FR3099771A1

FR3099771A1 - Full dense parts obtained by pressing hybrid titanium alloy powder by high velocity compaction and sintering in high vacuum

Info

Publication number: FR3099771A1
Application number: FR1906425A
Authority: FR
Original assignee: Metal Additive Tech; Metal Additive Technologies
Current assignee: Metal Additive Tech; Metal Additive Technologies
Priority date: 2019-06-14
Filing date: 2019-06-14
Publication date: 2021-02-12
Also published as: FR3099772B1; FR3099772A1

Abstract

A process for compressing an agglomerated spherical titanium alloy powder with dendritically titanium alloy powder, characterized in that the agglomerated powder is pressed by high velocity compaction with a ram speed superior to 2 m/s to a green body having high green density superior to 78%.A process for compressing an agglomerated spherical titanium alloy powder with dendritically titanium alloy powder, characterized in that the agglomerated powder is pressed by high velocity compaction with a ram speed superior to 2 m / s to a green body having high green density superior to 78% .

Description

Full dense parts obtained by pressing hybrid titanium alloy powder by high velocity compaction and sintering in high vacuumFull dense parts obtained by pressing hybrid titanium alloy powder by high velocity compaction and sintering in high vacuum

The present invention describes the process to achieve full theoretical density by pressing by high velocity compaction hybrid titanium powder without using any internal organic lubricant and sintering in high vacuum.The present invention describes the process to achieve full theoretical density by pressing by high velocity compaction hybrid titanium powder without using any internal organic lubricant and sintering in high vacuum.

Hybrid powder is denoted here as a mixture of spherical powder and dendritic powder or coral like morphology.Hybrid powder is denoted here as a mixture of spherical powder and dendritic powder or coral like morphology.

The spherical powder of titanium is issued by gas atomizing process, GA, by the plasma rotating electrode process, PREP, or by plasma atomization, PA.The spherical powder of titanium is issued by gas atomizing process, GA, by the plasma rotating electrode process, PREP, or by plasma atomization, PA.

The dendritic powder is issued from the Armstrong Process® (1).The dendritic powder is issued from the Armstrong Process® (1).

Titanium parts for aerospace and automotive applications represent a special interest because of their weight, excellent behavior in corrosive environment and good mechanical properties.Titanium parts for aerospace and automotive applications represent a special interest because of their weight, excellent behavior in corrosive environment and good mechanical properties.

In terms of technological aspects, the fabrication of titanium alloys by melting technology to produce ingots needs very good know how in order to obtain homogenous and high-quality ingots for conversion to mill products. Or, in practice, defects such as high interstitial defects, solute segregation, high density inclusions, beta flecks or voids which occurs during solidification cannot be avoided. The difficulty to control the solidification depends as well on the chemical composition of the alloy. The high reactivity of titanium conduct to formation of interstitial defects such as high concentration of oxygen, carbon or nitrogen. As well, the high-density inclusions occur by contamination of titanium alloy with raw material (molybdenum, tantalum, tungsten or tungsten carbides) used in the production of the alloy (2). Therefore, the presence of TiN in the microstructure decrease the fatigue performance of the material. As mentioned by (2), alloys which contains Beta eutectoid elements such as Fe, Ni, Mn, Cr and Cu have depressed freezing temperatures. This situation can lead to solute segregation during ingot solidification. The segregated areas can have a length up to several millimeters.In terms of technological aspects, the fabrication of titanium alloys by melting technology to produce ingots needs very good know how in order to obtain homogeneous and high-quality ingots for conversion to mill products. However, in practice, defects such as high interstitial defects, solute segregation, high density inclusions, beta flecks or voids which occurs during solidification cannot be avoided. The difficulty to control the solidification depends as well on the chemical composition of the alloy. The high reactivity of titanium conducts to formation of interstitial defects such as high concentration of oxygen, carbon or nitrogen. As well, the high-density inclusions occur by contamination of titanium alloy with raw material (molybdenum, tantalum, tungsten or tungsten carbides) used in the production of the alloy (2). Therefore, the presence of TiN in the microstructure decreases the fatigue performance of the material. As mentioned by (2), alloys which contain Beta eutectoid elements such as Fe, Ni, Mn, Cr and Cu have depressed freezing temperatures. This situation can lead to solute segregation during ingot solidification. The segregated areas can have a length up to several millimeters.

Once formed, these defects can be difficult to eliminate through all processing steps (2). The presence of this defects in their microstructure are detrimental to the mechanical behavior (3).Once formed, these defects can be difficult to eliminate through all processing steps (2). The presence of this defects in their microstructure are detrimental to the mechanical behavior (3).

One of the most known method used to convert the mill products in shaped components parts is forging technology. The forging technology allows to achieve the required microstructure through several thermo-mechanical processing steps. Table 1 highlight the processing steps in order to realize fully lamellar microstructure for the titanium Alpha - Beta alloys, such as example, titanium Ti-6Al-4Al (grade 5), Ti-6Al-2Zn-4Zr-2Mo-Si (Ti-6242) or Ti-6Al-6V-2Sn (Ti-662) (4).One of the most known method used to convert the mill products into shaped components parts is forging technology. The forging technology allows to achieve the required microstructure through several thermo-mechanical processing steps. Table 1 highlight the processing steps in order to realize fully lamellar microstructure for the titanium Alpha - Beta alloys, such as example, titanium Ti-6Al-4Al (grade 5), Ti-6Al-2Zn-4Zr-2Mo-Si (Ti- 6242) or Ti-6Al-6V-2Sn (Ti-662) (4).

Steps (4)Steps (4) HomogenizationHomogenization DeformationDeformation RecrystallizationRecrystallization AnnealingAnnealing lamellar microstructure Alpha-Beta alloyslamellar microstructure Alpha-Beta alloys realized above the Beta transus during several hoursrealized above the Beta transus during several hours Forging or rolling the material in the Beta phase field or in the Alpha phase fieldForging or rolling the material in the Beta phase field or in the Alpha phase field Realized 30°C -50°C above the Beta transus during several hours in order to control the Beta grain size (≈ 600 µm) (4).Realized 30°C -50°C above the Beta transus during several hours in order to control the Beta grain size (≈ 600 µm) (4). Realized in the Alpha + Beta phase field in order to age hardening the microstructure by the presence of Ti₃Al precipitates (4).
Realized in the Alpha + Beta phase field in order to age hardening the microstructure by the presence of Ti ₃ Al precipitates (4).
Table 1. Processing steps forTable 1. Processing steps for Alpha - BetaAlpha-Beta titanium alloys.titanium alloys.

To be noticed that the most important parameter in the recrystallization step is the cooling rate which will influence the grain size, Alpha lamellae, the thickness of Alpha layers at Beta grain boundaries. The Alpha lamellae and the size of Alpha colonies decrease with increasing cooling rate. The width of the Alpha lamellae decrease from 5 µm (in slowly cooled condition 1°C/ min) to 0.5 µm (in fast cooling condition 100°C/min). While the Alpha colonies size decrease from 300 µm to 100 µm in the same cooling conditions. As well, very fine grains “broken-up” structure can be obtained in the Beta processing condition by omitting the recrystallization steps. This is not so common commercially.To be noticed that the most important parameter in the recrystallization step is the cooling rate which will influence the grain size, Alpha lamellae, the thickness of Alpha layers at Beta grain boundaries. The Alpha lamellae and the size of Alpha colonies decrease with increasing cooling rate. The width of the Alpha lamellae decrease from 5 µm (in slowly cooled condition 1°C/min) to 0.5 µm (in fast cooling condition 100°C/min). While the Alpha colonies size decrease from 300 µm to 100 µm in the same cooling conditions. As well, very fine grains “broken-up” structure can be obtained in the Beta processing condition by omitting the recrystallization steps. This is not so common commercially.

As mentioned by (4), in the final step for the annealing heat treatment, the temperature is more important than holding time because the temperature determines whether age hardening of the α phase by Ti₃Al particles occurs or not. In the case of titanium alloy, Ti-6Al-4V (grade 5), aging at 500°C will precipitate the Ti₃Al particles.As mentioned by (4), in the final step for the annealing heat treatment, the temperature is more important than holding time because the temperature determines whether age hardening of the α phase by Ti ₃ Al particles occurs or not. In the case of titanium alloy, Ti-6Al-4V (grade 5), aging at 500°C will precipitate the Ti ₃ Al particles.

It is worth to mention that are critical parameters which determine the final microstructure such as: deformation time, deformation mode, deformation degree and the cooling rate (5). Those parameters are costly and influencing the shape of Beta grains, the recrystallized structure, the size of Alpha colonies and width of Alpha lamellae.It is worth to mention that are critical parameters which determine the final microstructure such as: deformation time, deformation mode, deformation degree and the cooling rate (5). Those parameters are costly and influencing the shape of Beta grains, the recrystallized structure, the size of Alpha colonies and width of Alpha lamellae.

Further, these shapes created by forging technology are finished by mechanical metal removal (machining) to the final design. From the economical point of view, the forging technology is costly in order to create a high-quality component part. The cost is increased by the extensively machining of the forged parts to create a complex light component. The requirement of machining is a consequence of two main reasons. Firstly, the inability to create a homogenous microstructure and secondly, the need to create a rectilinear shape known as “sonic shape” for ultrasonic investigation (2). It is common to obtain a finished part that weight less than 10% from the starting forged block (2).Further, these shapes created by forging technology are finished by mechanical metal removal (machining) to the final design. From the economical point of view, the forging technology is costly in order to create a high-quality component part. The cost is increased by the extensively machining of the forged parts to create a complex light component. The requirement of machining is a consequence of two main reasons. Firstly, the inability to create a homogeneous microstructure and secondly, the need to create a rectilinear shape known as “sonic shape” for ultrasonic investigation (2). It is common to obtain a finished part that weight less than 10% from the starting forged block (2).

Powder metallurgy route has been developed more and more in the last decades mainly because of their homogenous chemistry obtained on powder particles. According to (6), powder metallurgical route has a major advantage in terms of cost efficiency producing near net shapes with an efficiency of 80%. This is mainly because, little material removal for final design is necessary. In order to produce complex parts, the powder is used by different technologies such as additive manufacturing, metal injection molding, press and sintering, or hot isostatic pressing. Among those technologies the additive manufacturing technologies has a disadvantage in producing industrially scale complex parts because is limited by one hand by the processing time and by other hand because this technology requires very fine spherical powder inferior to 100 µm (7),(8),(9).Powder metallurgy route has been developed more and more in the last decades mainly because of their homogeneous chemistry obtained on powder particles. According to (6), powder metallurgical route has a major advantage in terms of cost efficiency producing near net shapes with an efficiency of 80%. This is mainly because, little material removal for final design is necessary. In order to produce complex parts, the powder is used by different technologies such as additive manufacturing, metal injection molding, press and sintering, or hot isostatic pressing. Among those technologies the additive manufacturing technologies has a disadvantage in producing industrially scale complex parts because is limited by one hand by the processing time and by other hand because this technology requires very fine spherical powder inferior to 100 µm (7),(8), (9).

Producing near net shape component by pressing of the powder and sintering from pre-alloyed powder seems a promising solution. Process technologies that can produce titanium powder such as plasma rotating electrode process, plasma atomization and gas atomizing process allows to obtain very clean chemistry with very low defects. Spherical powder titanium alloy grade 5 issued from the plasma rotating electrode process, gas atomizing process, or plasma atomization have a very clean chemistry with low oxygen content which can be inferior to 1500 ppm. Oxygen has a significant interstitial solubility in titanium. From one hand, the interstitial oxygen offers a strengthening effect, and by other hand it degrades the ductility. This is explained by the precipitation of Alpha from Beta leading to grain boundary alpha precipitates which are detrimental to ductility. Another reason, as mentioned by (10) is that the oxygen can induce oxygen enriched cluster or ordering and such microstructure inhomogeneities can block plastic deformation and as a consequence reduce ductility. For this reason, the oxygen content of ingot metallurgy Ti-6Al-4V is limited to 0.2% maximum (10).Producing near net shape component by pressing of the powder and sintering from pre-alloyed powder seems a promising solution. Process technologies that can produce titanium powder such as plasma rotating electrode process, plasma atomization and gas atomizing process allows to obtain very clean chemistry with very low defects. Spherical powder titanium alloy grade 5 issued from the plasma rotating electrode process, gas atomizing process, or plasma atomization have a very clean chemistry with low oxygen content which can be inferior to 1500 ppm. Oxygen has a significant interstitial solubility in titanium. From one hand, the interstitial oxygen offers a strengthening effect, and by other hand it degrades the ductility. This is explained by the precipitation of Alpha from Beta leading to grain boundary alpha precipitates which are detrimental to ductility. Another reason, as mentioned by (10) is that the oxygen can induce oxygen enriched cluster or ordering and such microstructure inhomogeneities can block plastic deformation and as a consequence reduce ductility. For this reason, the oxygen content of ingot metallurgy Ti-6Al-4V is limited to 0.2% maximum (10).

The spherical titanium powder with low oxygen content and their clean chemistry with low defects allow to achieve good mechanical properties if sintered density is close to the full theoretical density. Reason why, parts made from spherical powder represents a special interest for aerospace applications. Meanwhile, the spherical powder has bad behavior in terms of compaction because the resulted green body has low density and it is very difficult to reach full density after sintering.The spherical titanium powder with low oxygen content and their clean chemistry with low defects allow to achieve good mechanical properties if sintered density is close to the full theoretical density. Reason why, parts made from spherical powder represents a special interest for aerospace applications. Meanwhile, the spherical powder has bad behavior in terms of compaction because the resulted green body has low density and it is very difficult to reach full density after sintering.

In order to be compressed, the spherical powder needs to be mixed with a hydrocolloid binder before pressing. However, the green body has a low green strength, according to the standard ASTM B312 -14 (11) and needs care in order to be handled. Furthermore, in order to remove the organic binder from the green body, a debinding process is necessary to be carried prior to the sintering. The debinding process can be performed during 4 to 7 hours at a range temperature from 300ºC to 500ºC. To be noticed that the organic binder is not completely evaporated in the above-mentioned temperature range. Amines (CH-NH) or amides (CONH2) which represents 10% to 20% from the total molecule weight have a higher debinding temperature (700°C to 900°C). Those molecules are highly reactive with titanium and can lead to formation of carbides, nitrides and oxides in the matrix during the final densification. The presence of those carbides can be harmful for the mechanical behavior and cannot match the standard requirements for aerospace applications.In order to be compressed, the spherical powder needs to be mixed with a hydrocolloid binder before pressing. However, the green body has a low green strength, according to the standard ASTM B312 -14 (11) and needs care in order to be handled. Furthermore, in order to remove the organic binder from the green body, a debinding process is necessary to be carried prior to the sintering. The debinding process can be performed during 4 to 7 hours at a range temperature from 300ºC to 500ºC. To be noticed that the organic binder is not completely evaporated in the above-mentioned temperature range. Amines (CH-NH) or amides (CONH2) which represents 10% to 20% of the total molecule weight have a higher debinding temperature (700°C to 900°C). Those molecules are highly reactive with titanium and can lead to formation of carbides, nitrides and oxides in the matrix during the final densification. The presence of those carbides can be harmful for the mechanical behavior and cannot match the standard requirements for aerospace applications.

The high velocity compaction (HVC) technology is a powder compaction method which allows to obtain high densities of the compacted part. As mentioned by (5), the stage of compaction is 500-1000 times faster and that the ram speed of an HVC impact machine is in the range of 2- 30 m/s. Densification in HVC is achieved by intensive shockwaves created by a hydraulically-operated hammer, which transfers the compaction energy through the compaction tool to the powder [1 (2). (6) has noticed that the high velocity compaction technology is used to reach high density over 99.5 % by compaction of an agglomerated spherical powder with an organic binder. Or, in the case of titanium or titanium alloy, the presence of this organic binder in his composition can be harmful for the mechanical properties due of its high reactivity with carbon, nitrogen or oxygen from their molecules.The high velocity compaction (HVC) technology is a powder compaction method which allows to obtain high densities of the compacted part. As mentioned by (5), the stage of compaction is 500-1000 times faster and that the ram speed of an HVC impact machine is in the range of 2- 30 m/s. Densification in HVC is achieved by intensive shockwaves created by a hydraulically-operated hammer, which transfers the compaction energy through the compaction tool to the powder [1 (2). (6) has noticed that the high velocity compaction technology is used to reach high density over 99.5% by compaction of an agglomerated spherical powder with an organic binder. However, in the case of titanium or titanium alloy, the presence of this organic binder in its composition can be harmful for the mechanical properties due of its high reactivity with carbon, nitrogen or oxygen from their molecules.

From the point of view of cost & performance, high velocity compaction method presents a special interest because of high densities obtained and improved mechanical properties compared to conventional pressing and forging products.From the point of view of cost & performance, high velocity compaction method presents a special interest because of high densities obtained and improved mechanical properties compared to conventional pressing and forging products.

The geometry of the parts that can be produced by the high velocity compaction method is mentioned in (6).The geometry of the parts that can be produced by the high velocity compaction method is mentioned in (6).

The present invention has been focused to eliminate the organic binder from the mixing and as a consequence to eliminate the debinding process from the sintering cycle in order to reduce the costs. Moreover, the present invention has been focused to improve the mechanical properties of the pressed & sintered part. The pressing has been performed by high velocity compaction and sintering has been realized in high vacuum. The mechanical behavior fulfills the standards requirements for aerospace applications and are very competitive compared to ingot metallurgy parts.The present invention has been focused to eliminate the organic binder from the mixing and as a consequence to eliminate the debinding process from the sintering cycle in order to reduce the costs. Moreover, the present invention has been focused to improve the mechanical properties of the pressed & sintered part. The pressing has been performed by high velocity compaction and sintering has been realized in high vacuum. The mechanical behavior fulfills the standards requirements for aerospace applications and are very competitive compared to ingot metallurgy parts.

PREP powder PREP powder

Amstrong powder Armstrong powder

Measured porosity on sample 70% PREP-30% Armstrong Measured porosity on sample 70% PREP-30% Armstrong

Measured porosity on sample 70% PA-30% Armstrong Measured porosity on sample 70% PA-30% Armstrong

Microstructure on sample 70% PREP-30% Armstrong Microstructure on sample 70% PREP-30% Armstrong

Microstructure on sample 70% PA-30% Armstrong Microstructure on sample 70% PA-30% Armstrong

Spherical powderSpherical powder

Gaz atomized process (GA)Gas atomized process (GA)

A gas atomization process for titanium, was developed by Crucible Research Division of Crucible Materials Corporation in 1988 (13). In this process, the starting charge is induction skull melted under vacuum or an inert gas. The molten charge is then bottom poured into an induction heated nozzle and the resultant metal stream is atomized with high-pressure argon gas. The resulted droplets are rapidly solidified during cooling and allows formation of spherical powder particles with small satellites. The powder particles produced by the gas atomizing process lies from 10 µm till 500 µm and has a very good flowability. The oxygen content depends on the size of the particle powder. An average oxygen content of 0.06 % can be obtained on the coarser particle powder from 90 µm till 500 µm. While, an average oxygen content of 0.1 % can be meet on the smaller particle powder from 10 µm till 90 µm. The carbon, nitrogen and hydrogen do not depend on the particle size.A gas atomization process for titanium, was developed by Crucible Research Division of Crucible Materials Corporation in 1988 (13). In this process, the starting charge is induction skull melted under vacuum or an inert gas. The molten charge is then bottom poured into an induction heated nozzle and the resultant metal stream is atomized with high-pressure argon gas. The drop resultedlets are rapidly solidified during cooling and allows formation of spherical powder particles with small satellites. The powder particles produced by the gas atomizing process lie from 10 µm till 500 µm and has a very good flowability. The oxygen content depends on the size of the particle powder. An average oxygen content of 0.06 % can be obtained on the coarser particle powder from 90 µm till 500 µm. While, an average oxygen content of 0.1 % can be meet on the smaller particle powder from 10 µm till 90 µm. The carbon, nitrogen and hydrogen do not depend on the particle size.

Plasma rotating electrode process (PREP)Plasma rotating electrode process (PREP)

The plasma rotating electrode process, PREP, is a centrifugal atomization process for making titanium pre-alloyed powder developed by Nuclear Metals/Starmet (13). In this process, a helium plasma is used to melt the end of rapidly rotating bar. Molten droplets are spun off and solidify in flight in a helium atmosphere. The PREP powder is spherical and is presented in . The PREP powder has a very good flowability. The particle size is between 50 to 350 µm (10). The oxygen content on the PREP powder lies from 0.06 % till 0.15% and depends, as well, on the particle size. A higher oxygen content is meet on the smaller particle size inferior to 100 µm while a lower oxygen content is meet on the coarser powder superior to 100 µm.The plasma rotating electrode process, PREP, is a centrifugal atomization process for making titanium pre-alloyed powder developed by Nuclear Metals/Starmet (13). In this process, a helium plasma is used to melt the end of rapidly rotating bar. Molten droplets are spun off and solidify in flight in a helium atmosphere. The PREP powder is spherical and is presented in . The PREP powder has a very good flowability. The particle size is between 50 to 350 µm (10). The oxygen content on the PREP powder lies from 0.06% till 0.15% and depends, as well, on the particle size. A higher oxygen content is meet on the smaller particle size inferior to 100 µm while a lower oxygen content is meet on the coarser powder superior to 100 µm.

Plasma atomization (PA)Plasma atomization (PA)

In the plasma atomization process, a titanium wire is submitted to a non-transferred arc plasma torch. The high-velocity plasma melts the wire and breaks the liquid into fine droplets that solidify in flight. The powders produced by this process are spherical and has a particle size distribution from 5 µm till 250 µm. The oxygen content is inferior to 0.15% and as well depends on the particle size.In the plasma atomization process, a titanium wire is submitted to a non-transferred arc plasma torch. The high-velocity plasma melts the wire and breaks the liquid into fine droplets that solidify in flight. The powders produced by this process are spherical and has a particle size distribution from 5 µm till 250 µm. The oxygen content is inferior to 0.15% and as well depends on the particle size.

Dendritic powderDendritic powder

The Armstrong Process® [1] is a metal halide reduction process which allows formation of a titanium powder from titanium tetrachloride gaseous stream solution introduced into reaction with a stream of Natrium liquid solution. The reaction occurs as follow:The Armstrong Process® [1] is a metal halide reduction process which allows formation of a titanium powder from titanium tetrachloride gaseous stream solution introduced into reaction with a stream of Natrium liquid solution. The reaction occurs as follow:

TiCl₄(g)+ 4Na(l) → Ti(s)+ 4NaCl(s)TiCl ₄ (g)+ 4Na(l) → Ti(s)+ 4NaCl(s)

As well, other metal chlorides such as aluminum trichloride and vanadium tetrachloride can be introduced into the reaction stream to produce a homogeneous, pre-alloyed Ti-6Al-4V. The resulted powder has a dendritic, “coral-like” particle morphology and is presented in . The powder particle size lies from few microns till 250 µm. The powder issued from the Armstrong process have an oxygen content in the range from 0.12% till 0.2%, which matches the standard requirements for titanium grade 5 [1]. The powder has a high surface area to volume ratio and as a consequence offer very good behavior in terms of compressibility and green strength.As well, other metal chlorides such as aluminum trichloride and vanadium tetrachloride can be introduced into the reaction stream to produce a homogeneous, pre-alloyed Ti-6Al-4V. The powder resulted has a dendritic, “coral-like” particle morphology and is presented in . The powder particle size lies from a few microns till 250 µm. The powder issued from the Armstrong process has an oxygen content in the range from 0.12% till 0.2%, which matches the standard requirements for titanium grade 5 [1]. The powder has a high surface area to volume ratio and as a consequence offers very good behavior in terms of compressibility and green strength.

Two spherical powders issued from the PREP process and plasma atomization, PA respectively has been tested in these experiments.Two spherical powders issued from the PREP process and plasma atomization, PA respectively has been tested in these experiments.

The dendritic powder is issued from the Armstrong process.The dendritic powder is issued from the Armstrong process.

The chemical composition and particle size for all powders are presented in table 2.The chemical composition and particle size for all powders are presented in table 2.

GradeGrade Processprocess TiYou AlAl VV FeFe CVS NNOT HH OO Particle size
[µm]particle size
[µm] Ti-6Al-4VTi-6Al-4V PREPPREP Rest%Rest% 6.506.50 4.504.50 0.4000.400 0.0050.005 0.0500.050 0.0150.015 0.2000.200 88-15088-150 Ti-6Al-4VTi-6Al-4V PAPA Rest%Rest% 6.296.29 3.943.94 0.1480.148 0.0090.009 0.0160.016 0.0120.012 0.0740.074 <150<150 Ti-6Al-4VTi-6Al-4V Armstrongarmstrong Rest %Rest % 5.315.31 3.853.85 0.0050.005 0.0130.013 0.0060.006 0.0030.003 0.1380.138 <44<44 Ti-6Al-4V
Standard ASTM B988-13Ti-6Al-4V
Standard ASTM B988-13 Rest%Rest% 5.50-6.755.50-6.75 3.50-4.503.50-4.50 0.4
max0.4
max 0.080
max0.080
max 0.050 max0.050 max 0.015
max0.015
max 0.3
max0.3
max

Table 2. Chemical composition of tested powders.Table 2. Chemical composition of tested powders.

The agglomerated powder represents a mixture between spherical powder and dendritic powder. A total of 5 batches (mixtures) have been realized with different compositions in weight %, (60 to 90 % for spherical powder and 10 to 40% for dendritic powder). Here, the batch represent the agglomeration between spherical powder and dendritic powder.The agglomerated powder represents a mixture between spherical powder and dendritic powder. A total of 5 batches (mixtures) have been realized with different compositions in weight %, (60 to 90 % for spherical powder and 10 to 40% for dendritic powder). Here, the batch represents the agglomeration between spherical powder and dendritic powder.

The agglomeration has been blended in a mixer during 2 hours in order to homogenize the distribution of dendritic powder and spherical powder. It should be mentioned that no organic binder has been added to the mixture.The agglomeration has been blended in a mixer during 2 hours in order to homogenize the distribution of dendritic powder and spherical powder. It should be mentioned that no organic binder has been added to the mixture.

The green strength has been measured on every batch according to the standard ASTM B312 -14 and the results are presented in table 3.The green strength has been measured on every batch according to the standard ASTM B312 -14 and the results are presented in table 3.

Batchbatch Mixture in weight %Mixture in weight % Green strength [MPa]Green strength [MPa] 11 70% PA 30% Armstrong70% PA 30% Armstrong 4.14.1 22 90% PREP 10% Armstrong90% PREP 10% Armstrong 44 33 80% PREP 20% Armstrong80% PREP 20% Armstrong 77 44 70% PREP 30% Armstrong70% PREP 30% Armstrong 7.67.6 55 60% PREP 40% Armstrong60% PREP 40% Armstrong 1010

Table 3. Green strength resultsTable 3. Green strength results

As recommendation, in order to handle parts, the green strength should be superior to 4 MPa. It can be noticed that the green strength meets the requirements for handling the green parts. This result can be explained by a good repartition of dendritic powder thorough spherical powder which allows for spherical particles to have a good grip and as a consequence a good green strength. Moreover, the positive effect of adding dendritic powder it is observed on the mixture PREP/ Armstrong. The results show the green strength increases from 4 MPa to 10 MPa while the dendritic powder is added in the mixture from 10 % to 40% in weight.As recommendation, in order to handle parts, the green strength should be superior to 4 MPa. It can be noticed that the green strength meets the requirements for handling the green parts. This result can be explained by a good distribution of dendritic powder thorough spherical powder which allows for spherical particles to have a good grip and as a consequence a good green strength. Moreover, the positive effect of adding dendritic powder it is observed on the PREP/ Armstrong mixture. The results show the green strength increases from 4 MPa to 10 MPa while the dendritic powder is added in the mixture from 10 % to 40% in weight.

To be mentioned, that green strength has been measured separately on spherical powder and dendritic powder. The green strength on spherical powder was measured in two configurations: without organic binder and with organic binder (5% in weight). The green strength results obtained on the spherical powder without organic binder was 0 MPa. While, the green strength obtained on the spherical powder with organic binder was of 2 MPa.To be mentioned, that green strength has been measured separately on spherical powder and dendritic powder. The green strength on spherical powder was measured in two configurations: without organic binder and with organic binder (5% in weight). The green strength results obtained on the spherical powder without organic binder was 0 MPa. While, the green strength obtained on the spherical powder with organic binder was of 2 MPa.

The green strength measured on dendritic powder showed a value of 40 MPa.The green strength measured on dendritic powder showed a value of 40 MPa.

It can be concluded that using a dendritic powder improve significantly the green strength of the green part.It can be concluded that using a dendritic powder significantly improves the green strength of the green part.

Pressing by High Velocity Compaction (HVC)Pressing by High Velocity Compaction (HVC)

It has been decided to press cylinders samples with a diameter of 82 mm and a height of 13 mm by High Velocity Compaction (HVC). The HVC-machine used for this experiment is equipped with a hydraulic driven hammer and has a maximum capacity of 18 kJ. The ram speed used was superior to 2 m/s. To be mentioned that 2 pressing conditions has been tested: with a ram speed of 2 m/s and 4m/s. The samples pressed with a ram speed of 2 m/s (≈600 MPa) reached a relative density of 78 %. While the samples pressed with a ram speed superior to 4 m/s (≈1500 MPa) reached a relative density of 82%. Further in this presentation are showed the samples pressed with a ram speed superior to 4 m/s.It has been decided to press sample cylinders with a diameter of 82 mm and a height of 13 mm by High Velocity Compaction (HVC). The HVC-machine used for this experiment is equipped with a hydraulic driven hammer and has a maximum capacity of 18 kJ. The ram speed used was greater than 2 m/s. To be mentioned that 2 pressing conditions has been tested: with a ram speed of 2 m/s and 4m/s. The samples pressed with a ram speed of 2 m/s (≈600 MPa) reached a relative density of 78 %. While the samples pressed with a ram speed superior to 4 m/s (≈1500 MPa) reached a relative density of 82%. Further in this presentation are shown the samples pressed with a ram speed superior to 4 m/s.

A total of four cylinders samples from the batch 70% PA - 30% Armstrong and four cylinders samples from the batch 70%PREP-30% Armstrong has been pressed by HVC with a ram speed superior to 4 MPa. The average relative density results obtained on compacted cylinders by HVC are presented in table 3.A total of four cylinders samples from the batch 70% PA - 30% Armstrong and four cylinders samples from the batch 70%PREP-30% Armstrong has been pressed by HVC with a ram speed superior to 4 MPa. The average relative density results obtained on compacted cylinders by HVC are presented in table 3.

Batchbatch Mixture in weight %Mixture in weight % Relative density [%]Relative density [%] 11 70% PA 30% Armstrong70% PA 30% Armstrong 8282 44 70% PREP 30% Armstrong70% PREP 30% Armstrong 83.483.4

Table 4. Average results on compacted specimens by high velocity compaction.Table 4. Average results on compacted specimens by high velocity compaction.

SinteringSintering

The sintering cycle has been realized in a temperature range from 1200º to 1350°C in the high vacuum pressure from 10^-4Torr to 10^- ⁷ Torr with a holding time of 7 hours in order to obtain the full densification. A slow cooling has been realized in high vacuum during 24 hours in order to reach room temperature. Here, are presented the results obtained on sintered samples at 1300ºC for 7 hours followed by a slow cooling in high vacuum (24 hours) to reach room temperature.The sintering cycle has been realized in a temperature range from 1200º to 1350°C in the high vacuum pressure from 10^-4Torr to 10^- ⁷ Torr with a holding time of 7 hours in order to obtain the full densification. A slow cooling has been realized in high vacuum during 24 hours in order to reach room temperature. Here, are presented the results obtained on sintered samples at 1300ºC for 7 hours followed by a slow cooling in high vacuum (24 hours) to reach room temperature.

Porosity, microstructure and chemistryPorosity, microstructure and chemistry

Once the cylinder samples have been sintered the density, internal porosity and microstructure has been measured. The apparent density has been measured by Archimedes technique according to the standard ASTM B-311-17 (14). All cylinder samples have reached a relative density superior to 99.5 %. The average porosity has been measured by cross section image analysis. shows the porosity obtained on sintered cylinder from the batch 70% PREP-30% Armstrong while the show the porosity measured on sintered cylinder from the batch 70% PA -30 % Armstrong. It can be noticed that the samples are close to the full theoretical density and confirm the results obtained by Archimedes technique. The average porosity measured on the sample 70%PREP-30%Amstrong it is 0.014 % ± 0.001. While, the average porosity measured on the sample 70%PA-30% Armstrong has a value of 0.03 %±0.001.Once the cylinder samples have been sintered the density, internal porosity and microstructure has been measured. The apparent density has been measured by Archimedes technique according to the standard ASTM B-311-17 (14). All cylinder samples have reached a relative density greater than 99.5%. The average porosity has been measured by cross section image analysis. shows the porosity obtained on sintered cylinder from the batch 70% PREP-30% Armstrong while the show the porosity measured on sintered cylinder from the batch 70% PA -30 % Armstrong. It can be noticed that the samples are close to the full theoretical density and confirm the results obtained by Archimedes technique. The average porosity measured on the sample 70%PREP-30%Amstrong it is 0.014% ± 0.001. While, the average porosity measured on the sample 70%PA-30% Armstrong has a value of 0.03%±0.001.

It can be observed that the microstructure on both samples as shown in and consist in a typical Widman-stätten structure with acicular alpha grains and intergranular beta. On the samples 70 % PREP-30% the average Alpha lamellae size is 5 µm while the Alpha colonies are around 100 µm in size. Those are consistent with the slow cooling rate performed which allowed to avoid the pick up the oxygen during the cooling. Meanwhile, the microstructure observed on the sample 70 PA-30% Armstrong is finer (2 µm for Alpha lamellae width and 80 µm for the Alpha colonies). This can be explained by a lower oxygen content for the PA powder as received, approximately 0.07%, comparably with the PREP which was 0.2% (see table 2). To be mentioned that no carbides were observed on sintered microstructures.It can be observed that the microstructure on both samples as shown in and consist in a typical Widman-stätten structure with acicular alpha grains and intergranular beta. On the samples 70% PREP-30% the average Alpha lamellae size is 5 µm while the Alpha colonies are around 100 µm in size. Those are consistent with the slow cooling rate performed which allowed to avoid the pick up the oxygen during the cooling. Meanwhile, the microstructure observed on the sample 70 PA-30% Armstrong is finer (2 µm for Alpha lamellae width and 80 µm for the Alpha colonies). This can be explained by a lower oxygen content for the PA powder as received, approximately 0.07%, comparably with the PREP which was 0.2% (see table 2). To be mentioned that no carbides were observed on sintered microstructures.

The chemical analysis was performed on sintered samples using a Leco analyzer type ONH836 for oxygen and nitrogen and a Leco type CS444 for carbon measurements. The analyses were performed according to the standard ASTM E1409 (15) to identify the oxygen and nitrogen content, the standard ASTM E1447 (16) was used to analyze the hydrogen. Finally, the standard ASTM E 1941 (17) has been used to measure the carbon content. The results are presented in table 5 and compared with the standards ASTM B988-13 (18) and ASTM B-348-13 (19):The chemical analysis was performed on sintered samples using a Leco analyzer type ONH836 for oxygen and nitrogen and a Leco type CS444 for carbon measurements. The analyzes were performed according to the standard ASTM E1409 (15) to identify the oxygen and nitrogen content, the standard ASTM E1447 (16) was used to analyze the hydrogen. Finally, the standard ASTM E 1941 (17) has been used to measure the carbon content. The results are presented in table 5 and compared with the standards ASTM B988-13 (18) and ASTM B-348-13 (19):

ElementsItems TiYou AlAl VV FeFe OO NNOT CVS HH 70%PREP/30%Armstrong70%PREP/30%Armstrong restrest 66 3.83.8 0.40.4 0.1400.140 0.0110.011 0.0210.021 0.010.01 70%PA/30%Armstrong70%PA/30%Armstrong restrest 66 3.93.9 0.140.14 0.1400.140 0.0100.010 0.020.02 0.010.01 ASTM B-988 13 maxASTM B-988 13 max restrest 5.5-6.755.5-6.75 3.5-4.53.5-4.5 0.40.4 0.30.3 0.050.05 0.080.08 0.0150.015 ASTM B-348-13 maxASTM B-348-13 max restrest 5.5-6.755.5-6.75 3.5-4.53.5-4.5 0.40.4 0.20.2 0.050.05 0.080.08 0.0150.015

Table 5. Chemical analysis in weight % obtained on sintered samples compared to standards.Table 5. Chemical analysis in weight % obtained on sintered samples compared to standards.

The analysis results from the table 5 put in evidence that the oxygen pick-up during sintering was kept as in the received powder (see table 2). Moreover, the oxygen content is inferior to 0.2 % (imposed as maximum allowance content by the standard ASTM B-348-13). This can be explained by the high vacuum at 10^-6Torr which prevented the oxidation during the sintering. In conclusion the chemical composition of the sintered parts fulfills all the requirements as required by the standard ASTM B-348-13 and ASTM B988-13.The analysis results from the table 5 put in evidence that the oxygen pick-up during sintering was kept as in the received powder (see table 2). Moreover, the oxygen content is inferior to 0.2 % (imposed as maximum allowance content by the standard ASTM B-348-13). This can be explained by the high vacuum at 10 ^-6 Torr which prevented the oxidation during the sintering. In conclusion the chemical composition of the sintered parts fulfills all the requirements as required by the standard ASTM B-348-13 and ASTM B988-13.

Mechanical testingMechanical testing

From the sintered cylinders, two tensile specimens were machined in order to test the mechanical behavior. The tensile testing machine used for these experiments is type Zwick/Roell Z250. The tensile testing was carried out in accordance with standard SS EN 6892. The tensile test piece used is type 6B30. The tensile tests were performed at room temperature. The mechanical properties results are presented in table 5 and compared to grade 5 ASTM B-988-13 and ASTM B-348-13. It should be mentioned that the standard B-988-13 is required for the powder metallurgy titanium and titanium structural components. While the standard B-348-13 is required for the annealed titanium and titanium alloys bar and billets.From the sintered cylinders, two tensile specimens were machined in order to test the mechanical behavior. The tensile testing machine used for these experiments is type Zwick/Roell Z250. The tensile testing was carried out in accordance with standard SS EN 6892. The tensile test piece used is type 6B30. The tensile tests were performed at room temperature. The mechanical properties results are presented in table 5 and compared to grade 5 ASTM B-988-13 and ASTM B-348-13. It should be mentioned that the standard B-988-13 is required for the powder metallurgy titanium and titanium structural components. While the standard B-348-13 is required for the annealed titanium and titanium alloys bar and tickets.

Titanium
Grade 5Titanium
Grade 5 Yield strength
Rp_0.2
[N/mm²]Yield strength
Rp _0.2
[N/ ^mm2 ] Tensile strength
Rm
[N/mm²]Tensile strength
rm
[N/ ^mm2 ] Elongation A
[%]Elongation A
[%] Reduction Area
Z [%]Reduction Area
Z[%] PREP/ArmstrongPREP/Armstrong 915915 10401040 1212 3030 PA/armstrongPA/armstrong 910910 10271027 1212 3030 Grade 5
ASTM B 988-13
Min requirements
Grade 5
ASTM B988-13
Minimum requirements
745745 810810 99 >=23>=23 Grade 5
ASTM B 348-13
Min requirements
Grade 5
ASTM B348-13
Minimum requirements
828828 895895 1010 >=25>=25 Grade 5
Typical values
Grade 5
Typical values
890±30890±30 970±30970±30 14±214±2 >=25>=25

Table 6. Mechanical results obtained on sintered samples PA/Armstrong and PREP/Armstrong compared to grade 5 ASTM B-348 and ASTM 988-13Table 6. Mechanical results obtained on sintered samples PA/Armstrong and PREP/Armstrong compared to grade 5 ASTM B-348 and ASTM 988-13

The mechanical properties as shown in table 6 shows that yield tensile strength, ultimate tensile strength and elongation obtained on sintered samples on both types of samples are significant superior to the standard requirements ASTM B-988-14 necessary for powder metallurgy titanium alloys parts. Moreover, the results obtained in those tests shows that are slightly superior to the values required by the standard ASTM B-348-13 necessary for annealed titanium parts. Those results can be explained by a low oxygen content in sintered material and homogenous microstructure.The mechanical properties as shown in table 6 shows that yield tensile strength, ultimate tensile strength and elongation obtained on sintered samples on both types of samples are significant superior to the standard requirements ASTM B-988-14 necessary for powder metallurgy titanium alloys parts. Moreover, the results obtained in those tests shows that are slightly superior to the values required by the standard ASTM B-348-13 necessary for annealed titanium parts. Those results can be explained by a low oxygen content in sintered material and homogeneous microstructure.

The present invention put in evidence a very good cost efficiency. Mainly, because the debinding process is eliminated from the process and no organic binder was used in the agglomeration.The present invention put in evidence a very good cost efficiency. Mainly, because the debinding process is eliminated from the process and no organic binder was used in the agglomeration.

Moreover, a study accomplished by Metafensch a research institute specialized in research for metallurgy in industry for the life cycle product putted in evidence:Moreover, a study accomplished by Metafensch a research institute specialized in research for metallurgy in industry for the life cycle product putted in evidence:

loss of 15 % of material in the atomization process in order to produce the powderloss of 15% of material in the atomization process in order to produce the powder

a material removal inferior to 3 % in order to produce near net shapes using the MMS Scanpac® the process.a material removal inferior to 3 % in order to produce near net shapes using the MMS Scanpac® the process.

a loss of 10 to 20 % material in order to produce a finished part by material removing process (machining).a loss of 10 to 20 % material in order to produce a finished part by material removing process (machining).

Therefore, compared to forging technology which represent an efficiency of 10 % in order to produce a finished part, the presented process, represent an efficiency superior to 60%.Therefore, compared to forging technology which represents an efficiency of 10% in order to produce a finished part, the presented process, represents an efficiency superior to 60%.

ReferencesReferences

(1) K. Araci, D. Mangabhai, K. Akhtar, 9 - Production of titanium by the Armstrong Process®, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 149-162, ISBN 9780128000540(1) K. Araci, D. Mangabhai, K. Akhtar, 9 - Production of titanium by the Armstrong Process®, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 149-162, ISBN 9780128000540

(2) G. Lütjering, J.C. Williams “Titanium” second edition, 3 - technological aspects Springer, 2007, pages 53-173, ISBN 978-3-540-71397-5(2) G. Lütjering, J.C. Williams “Titanium” second edition, 3 - technological aspects Springer, 2007, pages 53-173, ISBN 978-3-540-71397-5

3] R. Boyer, E.W. Collings, and G. Welsch: “Materials Properties Handbook: Titanium Alloys”, 1994, ISBN 978-0-87170-481-83] R. Boyer, E.W. Collings, and G. Welsch: “Materials Properties Handbook: Titanium Alloys”, 1994, ISBN 978-0-87170-481-8

(4) G. Lütjering, J.C. Williams “Titanium” second edition, 5 – Alpha + Beta alloys Springer, 2007, pages 203-258, ISBN 978-3-540-71397-5(4) G. Lütjering, J.C. Williams “Titanium” second edition, 5 – Alpha + Beta alloys Springer, 2007, pages 203-258, ISBN 978-3-540-71397-5

(5) N. Gey, M. Humbert, M.J. Philippe, Y. Combres, Investigation of the α- and β- texture evolution of hot rolled Ti-64 products, Materials Science and Engineering: A, Volume 219, Issues 1–2, 1996, Pages 80-88, ISSN 0921-5093(5) N. Gey, M. Humbert, MJ Philippe, Y. Combres, Investigation of the α- and β- texture evolution of hot rolled Ti-64 products, Materials Science and Engineering: A, Volume 219, Issues 1–2 , 1996, Pages 80-88, ISSN 0921-5093

(6) Chrier Åslund, “Multilevel parts from agglomerated spherical powder”, patent US2015239045(6) Chrier Åslund, “Multilevel parts from agglomerated spherical powder”, patent US2015239045

(7) F. Nobuo: “Titanium- Based Powder, Titanium based ingot obtained by fusing titanium- based powder, and titanium based sintered article obtained by sintering titanium-based powder” patent JP2018145467.(7) F. Nobuo: “Titanium-Based Powder, Titanium based ingot obtained by fusing titanium-based powder, and titanium based sintered article obtained by sintering titanium-based powder” patent JP2018145467.

(8) F. Nobuo: “Titanium based powder and ingot and sintered ingot thereof”, patent US2018021854(8) F. Nobuo: “Titanium based powder and ingot and sintered ingot thereof”, patent US2018021854

(9) S. Knittek, G. Fribourg. “Composition for manufacturing parts from titanium aluminide by powder sintering, and manufacturing method using such a composition” patent US2018112293(9) S. Knittek, G. Freiburg. “Composition for manufacturing parts from titanium aluminide by powder sintering, and manufacturing method using such a composition” patent US2018112293

(10) M. Yan, H.P. Tang, M. Qian, 15 - Scavenging of oxygen and chlorine from powder metallurgy (PM) titanium and titanium alloys, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 253-276, ISBN 9780128000540(10) M. Yan, HP Tang, M. Qian, 15 - Scavenging of oxygen and chlorine from powder metallurgy (PM) titanium and titanium alloys, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 253-276, ISBN 9780128000540

(11) ASTM B312 -14 Standard Test Method for Green Strength of Specimens Compacted from Metal Powders, ASTM International, West Conshohocken, PA, 2014(11) ASTM B312 -14 Standard Test Method for Green Strength of Specimens Compacted from Metal Powders, ASTM International, West Conshohocken, PA, 2014

(12) P. Skoglund, M. Kejzelman, I. Hauer “High density components PM by high velocity compaction” PM2 TEC, Orlando, USA, 2002(12) P. Skoglund, M. Kejzelman, I. Hauer “High density components PM by high velocity compaction” PM2 TEC, Orlando, USA, 2002

(13) C.F. Yolton, Francis H.Froes, 2 - Conventional titanium powder production, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 21-32, ISBN 9780128000540.(13) CF Yolton, Francis H. Froes, 2 - Conventional titanium powder production, Editor(s): Ma Qian, Francis H. (Sam) Froes, Titanium Powder Metallurgy, Butterworth-Heinemann, 2015, Pages 21-32, ISBN 9780128000540.

(14) ASTM B311-17, Standard Test Method for Density of Powder Metallurgy (PM) Materials Containing Less Than Two Percent Porosity, ASTM International, West Conshohocken, PA, 2017(14) ASTM B311-17, Standard Test Method for Density of Powder Metallurgy (PM) Materials Containing Less Than Two Percent Porosity, ASTM International, West Conshohocken, PA, 2017

(15) ASTM E1409-13, Standard Test Method for Determination of Oxygen and Nitrogen in Titanium and Titanium Alloys by Inert Gas Fusion, ASTM International, West Conshohocken, PA, 2013(15) ASTM E1409-13, Standard Test Method for Determination of Oxygen and Nitrogen in Titanium and Titanium Alloys by Inert Gas Fusion, ASTM International, West Conshohocken, PA, 2013

(16) ASTM E1447-09(2016), Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion Thermal Conductivity/Infrared Detection Method, ASTM International, West Conshohocken, PA, 2016(16) ASTM E1447-09(2016), Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion Thermal Conductivity/Infrared Detection Method, ASTM International, West Conshohocken, PA, 2016

(17) ASTM E1941-10(2016), Standard Test Method for Determination of Carbon in Refractory and Reactive Metals and Their Alloys by Combustion Analysis, ASTM International, West Conshohocken, PA, 2016,(17) ASTM E1941-10(2016), Standard Test Method for Determination of Carbon in Refractory and Reactive Metals and Their Alloys by Combustion Analysis, ASTM International, West Conshohocken, PA, 2016,

(18) ASTM B988-13 Standard specification for powder metallurgy titanium and titanium alloy structural component, ASTM International, West Conshohocken, PA, 2013.(18) ASTM B988-13 Standard specification for powder metallurgy titanium and titanium alloy structural component, ASTM International, West Conshohocken, PA, 2013.

(19) ASTM B-348-13 Standard specification for titanium and titanium alloys bar and billets, ASTM International, West Conshohocken, PA, 2013.(19) ASTM B-348-13 Standard specification for titanium and titanium alloys bar and billets, ASTM International, West Conshohocken, PA, 2013.

Claims

A process for compressing an agglomerated spherical titanium alloy powder with dendritically titanium alloy powder, characterized in that the agglomerated powder is pressed by high velocity compaction with a ram speed superior to 2 m/s to a green body having high green density superior to 78%.A process for compressing an agglomerated spherical titanium alloy powder with dendritically titanium alloy powder, characterized in that the agglomerated powder is pressed by high velocity compaction with a ram speed superior to 2 m/s to a green body having high green density superior to 78% .

A process according to claim 1, where the spherical powder is in amount of 60% to 90% in weight and the dendritically powder is in amount 10% to 40%.A process according to claim 1, where the spherical powder is in amount of 60% to 90% in weight and the dendritically powder is in amount 10% to 40%.

A process according to claim 1 and 2, where there is no used internal binder.A process according to claim 1 and 2, where there is no used internal binder.

A process according to the claim 1 to 3, wherein the ram speed is superior to 4 m/s and a pressure of 600-1500 MPa.A process according to the claim 1 to 3, wherein the ram speed is superior to 4 m/s and a pressure of 600-1500 MPa.

A process according to the claim 1 to 4, wherein the spherical titanium alloy powder is obtained from the PREP process, the PA process or the GA process.A process according to the claim 1 to 4, wherein the spherical titanium alloy powder is obtained from the PREP process, the PA process or the GA process.

A process according to the claim 1 to 5, wherein the dendritically titanium alloy powder is obtained from the Armstrong process.A process according to the claim 1 to 5, wherein the dendritically titanium alloy powder is obtained from the Armstrong process.

A process for the preparation of the sintered product from the agglomerated spherical powder and dendritically powder with no organic binder pressed by high velocity compaction with a ram speed superior to 2 m/s and a pressure of 600 - 1500 MPa and the sintering is realized in a reducing atmosphere with a vacuum pressure in the range 10^-4Torr to 10^-7Torr and the sintering temperature is preformed in the range 1200°C - 1350°C in accordance with any claims 1 to 6 and said green body is sintered to full or near full theoretical density, ie at least 99% of the full theoretical density, preferably at least 99.9%.A process for the preparation of the sintered product from the agglomerated spherical powder and dendritically powder with no organic binder pressed by high velocity compaction with a ram speed superior to 2 m/s and a pressure of 600 - 1500 MPa and the sintering is realized in a reducing atmosphere with a vacuum pressure in the range 10 ^-4 Torr to 10 ^-7 Torr and the sintering temperature is preformed in the range 1200°C - 1350°C in accordance with any claims 1 to 6 and said green body is sintered to full or near full theoretical density, ie at least 99% of the full theoretical density, preferably at least 99.9%.