CN113814604B

CN113814604B - Eutectic high-entropy alloy solder for brazing titanium, titanium alloy and stainless steel

Info

Publication number: CN113814604B
Application number: CN202111188128.1A
Authority: CN
Inventors: 李鹏; 董红刚; 李超; 孙浩田
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2021-10-12
Filing date: 2021-10-12
Publication date: 2023-01-17
Anticipated expiration: 2041-10-12
Also published as: CN113814604A

Abstract

The invention provides a titanium alloyAnd an eutectic high-entropy alloy solder brazed by titanium alloy and stainless steel and a preparation method thereof. The eutectic high-entropy alloy brazing filler metal is Al _x CoCrCuNi _1+x The eutectic high-entropy alloy solder is composed of the following raw material components in atomic percentage: 10 to 20 percent of Al, 10 to 20 percent of Co, 10 to 20 percent of Cr, 10 to 20 percent of Cu and 25 to 35 percent of Ni, wherein the sum of the atomic percentages of the components is 100 percent. The invention also discloses a preparation method of the brazing filler metal. The eutectic high-entropy alloy solder provided by the invention has the advantages of good fluidity and wettability, stable structure components, less brittle intermetallic compounds of welded joints and the like.

Description

Eutectic high-entropy alloy solder for brazing titanium, titanium alloy and stainless steel

Technical Field

The invention relates to the technical field of welding materials, in particular to an eutectic high-entropy alloy solder for brazing titanium, titanium alloy and stainless steel and a preparation method thereof.

Background

The titanium alloy has the excellent characteristics of high strength, high toughness, high corrosion resistance, low thermal conductivity, low density and the like, and is widely applied to the fields of aerospace, energy and chemical industry and the like. But the titanium alloy has higher smelting processing difficulty and higher price. Stainless steel has excellent corrosion resistance, good comprehensive mechanical property and low price, and is widely applied to industry. Therefore, the high-quality connector of titanium or titanium alloy and stainless steel has wide application prospect in the fields of nuclear industry, petrochemical industry and aerospace due to relatively low cost, high corrosion resistance and good mechanical property. However, the metallurgical compatibility between titanium alloy and stainless steel dissimilar metal is very poor, and brittle Ti-Fe intermetallic compounds are easily formed to seriously deteriorate the performance of the joint.

Vacuum brazing is a common dissimilar metal welding method, and can realize high-precision and small-deformation dissimilar material connection. In the vacuum brazing process, the type and the form of brazing filler metal are important links for realizing high-quality joints. The alloy component with the highest component ratio in the brazing filler metal is called a basic component, one or two core elements are usually selected as the basic component of the brazing filler metal for titanium/steel vacuum brazing, and the performance of the brazing filler metal is regulated and controlled by adding a small amount of alloying elements.

At present, ag or Ti with better metallurgical compatibility with a base metal is mainly used as a basic component in titanium/steel brazing vacuum welding, and other small amount of elements are added to prepare the silver-based brazing filler metal and the titanium-based brazing filler metal. However, the silver-based brazing filler metal has high cost and poor corrosion resistance of joints, and the titanium-based brazing filler metal is easy to generate Ti-Fe brittle intermetallic compounds to reduce brazing seam performance. Therefore, the brazing filler metal taking a single core element as a basic component has some defects in the development of realizing high-performance vacuum brazing joints of titanium/steel dissimilar metals.

The high-entropy alloy is an alloy with a simple solid solution structure prepared by utilizing the high mixed entropy of a multi-principal-element alloy system, and has the advantages of stable structure, good corrosion resistance and stable high-temperature mechanical property.

Therefore, there is a need to develop a solder prepared by utilizing the high entropy effect of high entropy alloy, so as to reduce the formation of intermetallic compounds and realize the high-efficiency connection of titanium and titanium alloy and stainless steel dissimilar metal joint through multi-component synergistic action.

Disclosure of Invention

According to the technical problems, the eutectic high-entropy alloy solder for brazing titanium and titanium alloy and stainless steel and the preparation method thereof are provided. Al of the invention _x CoCrCuNi _1+x The eutectic high-entropy alloy solder has the advantages of good fluidity and wettability, stable structure components, less brittle intermetallic compounds of a welding joint and the like, and is particularly suitable for vacuum brazing of titanium, titanium alloy and stainless steel.

The technical means adopted by the invention are as follows:

eutectic high-entropy alloy brazing filler metal for brazing titanium, titanium alloy and stainless steel, wherein the brazing filler metal is Al _x CoCrCuNi _1+x The eutectic high-entropy alloy solder is composed of the following raw material components in atomic percentage:

10 to 20 percent of Al, 10 to 20 percent of Co, 10 to 20 percent of Cr, 10 to 20 percent of Cu and 25 to 35 percent of Ni, wherein the sum of the atomic percentages of the components is 100 percent. Wherein x represents the molar ratio of Al to Co, cr and Cu elements, namely the molar ratio of Al to Co to Cr to Cu to Ni is x: 1.

Further, the Al, co, cr, cu, and Ni are pure metal particles having a purity of 99.99%.

The invention also discloses a preparation method of the eutectic high-entropy alloy solder for brazing titanium, titanium alloy and stainless steel, which comprises the following steps,

step 1: placing a high-purity metal raw material into a 99.5% absolute ethyl alcohol solution, performing ultrasonic cleaning by using an ultrasonic cleaning machine, and drying for later use;

and 2, step: using an electronic balance with the precision of 0.001g, respectively weighing the following raw materials in atomic percent: 10 to 20 percent of Al, 10 to 20 percent of Co, 10 to 20 percent of Cr, 10 to 20 percent of Cu and 25 to 35 percent of Ni, wherein the sum of the atomic percentages of the components is 100 percent;

and 3, step 3: sequentially putting Al, cu, ni, co and Cr raw materials into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the raw materials in the step 2, and putting a pure titanium block into a crucible B of the vacuum arc melting furnace;

and 4, step 4: vacuumizing the vacuum arc melting furnace, filling high-purity argon into the furnace chamber, melting the pure titanium block placed in the step 3 in a crucible B by using electric arc to remove residual oxygen in the furnace, and then melting the sample in the crucible A to obtain an eutectic high-entropy alloy button ingot;

and 5: and (4) preparing the eutectic high-entropy alloy button ingot obtained in the step (4) into an alloy solder foil strip by using a single-roller rapid solidification device.

Furthermore, the purity of the high-purity metal raw material is more than 99.99 wt%.

Further, in step 4, the vacuum environment is 5 × 10 ^-3 Pa or less.

Further, in the step 4, the pure titanium block placed in the crucible B is smelted by using an electric arc, and the electric arc current is 100-120A and the duration is 15-30s.

Further, in step 4, the current for melting the samples in the crucible A ranges from 150A to 200A, and the melting is repeated at least 5 times for each sample.

Further, in the step 5, the roller rotating speed of the single-roller rapid solidification device is 10-30m/s, and the thickness of the prepared foil tape is about 30-100 mu m.

Compared with the prior art, the invention has the following advantages:

1. aiming at the defects of poor fluidity, poor casting performance, serious segregation and the like of the existing single-phase solid solution alloy, al is designed and prepared _x CoCrCuNi _1+x Eutectic high-entropy alloy solder. The eutectic high-entropy alloy has the advantages of good fluidity and excellent casting performance of the eutectic alloy, and is convenient for preparing the brazing filler metal foil strip;

2. the eutectic high-entropy alloy solder belongs to multi-principal-element alloy, in order to enable the structure of the high-entropy alloy to be an eutectic structure, pseudo-binary combination of AlNi and CoCrNi is adopted, cu is added to improve the performance of the alloy, the designed solder structure is a two-phase solid solution structure, and the structure components are uniform. The high mixed entropy of the multi-principal-element alloy can effectively improve the metallurgical reaction of the joint interface and inhibit the generation of brittle intermetallic compounds in the welding seam;

3. al of the invention _x CoCrCuNi _1+x The addition of Cu element in the brazing filler metal can slowly release the stress between two components of AlNi-CoCrNi in the preparation process of the high-entropy alloy, effectively improve the plasticity of the alloy and enhance the forming capability of the brazing filler metal;

4. the melting point of the eutectic high-entropy alloy solder is obviously higher than that of the common Ag-based, al-based and Ti-Cu-based solders, and the high-temperature service performance of the titanium/steel vacuum soldered joint can be effectively improved.

In conclusion, the design concept of the brazing filler metal alloy provided by the invention can be widely applied to preparation of dissimilar metal welding brazing filler metal.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 shows Al _1.0 CoCrCuNi _2.0 XRD pattern of high entropy alloy.

FIG. 2 is Al _1.0 CoCrCuNi _2.0 DSC curve of high entropy alloy.

FIG. 3 shows the metallographic structure of the high-entropy alloy solder obtained in example 3 of the invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The invention provides Al for brazing titanium, titanium alloy and stainless steel _x CoCrCuNi _1+x The eutectic high-entropy alloy solder is particularly suitable for vacuum brazing and comprises the following components in atomic percentage: al (aluminum)10 to 20 percent of Co, 10 to 20 percent of Cr, 10 to 20 percent of Cu and 25 to 35 percent of Ni, wherein the sum of the atomic percentages of the components is 100 percent.

The reasons for limiting the components and the contents of the eutectic high-entropy alloy solder are as follows:

the invention adopts a pseudo-binary eutectic design concept, fully considers the element metallurgical reaction and chemical compatibility of each component of the brazing filler metal and parent metals on two sides, and utilizes the high mixed entropy of a multi-principal-element system to inhibit the formation of intermetallic compounds in the welding seam. In the multi-element alloy system, when the components are mixed in equal atomic ratio, the maximum configuration entropy is obtained, so that the components are in equal atomic ratio in the design. Al and Ni elements have strong affinity with Ti elements, and the Al and Ni elements have large negative mixed enthalpy and are easy to form a stable phase, so that AlNi with equal atomic ratio is taken as a component during component design; co, cr and Ni elements are completely dissolved in solid solution with Fe elements, the Co, cr and Ni elements have approximate atomic radii and small enthalpy of mixing between atom pairs, so CoCrNi with equal atomic ratio is used as a second component; the Cu element is segregated in the intergranular mode, so that the internal stress in the alloy can be weakened, and the plasticity of the alloy is effectively improved. The optimal solder proportioning is realized by regulating and controlling the AlNi-CoCrNiCu two-component proportion, namely the atomic ratio of the solder components is 1+ x for Al to Co to Cr to Cu to Ni =1 to 1.

Al provided by the invention _x CoCrCuNi _1+x The preparation method of the eutectic high-entropy alloy solder is implemented according to the following steps:

step 1: the high-purity metal raw material is placed in a 99.5% absolute ethyl alcohol solution to be subjected to ultrasonic cleaning by using an ultrasonic cleaning machine and is dried by using a vacuum drying oven. The method is mainly used for removing the possible pollution on the surface of the high-purity raw material in the storage process, such as oil stain, dust and the like.

And 2, step: using an electronic balance with the precision of 0.001g, weighing the following raw materials (with the purity of more than 99.99%) according to atomic percentage:

10 to 20 percent of Al, 10 to 20 percent of Co, 10 to 20 percent of Cr, 10 to 20 percent of Cu and 25 to 35 percent of Ni, wherein the sum of the atomic percentages of the components is 100 percent. The accuracy of the alloy composition is ensured to the maximum extent.

And step 3: and (3) sequentially putting the raw materials of Al, cu, ni, co and Cr into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the step 2. And a pure titanium block is placed in a crucible B of the vacuum smelting furnace. The metal with low melting point is arranged at the bottom of the crucible, so that the burning loss of the low melting point element caused by overhigh arc temperature in the smelting process is reduced, and the stability of the alloy components is further ensured.

And 4, step 4: vacuumizing the vacuum arc melting furnace to 5 x 10 ^-3 And (5) filling high-purity argon into the furnace chamber below Pa. The pure titanium block placed in step 3 was melted in crucible B using an arc with an arc current of 100A for a duration of 20s. Then, the samples in the crucible A are smelted, the current ranges from 150A to 200A, and smelting is repeated for at least 5 times for each sample. The pure titanium block is used for consuming the oxygen remained in the furnace chamber of the vacuum melting furnace. The purpose of repeated melting of the sample is to make the composition of the alloy ingot uniform and the structure stable.

And 5: and (4) preparing the eutectic high-entropy alloy button ingot obtained in the step (4) into an alloy solder foil strip with the thickness of about 30-100 microns by using a single-roller rapid solidification device and the linear speed of a roller of 10-30 m/s. The brazing filler metal foil belt with good forming and smooth surface is obtained by reasonably adjusting the rotating speed of the roller in the single-roller rapid solidification device, and the poor forming quality of the foil belt can be caused by too high or too low rotating speed.

Table 1 below lists the contents of the various components in examples 1-4:

TABLE 1 brazing filler metals in examples 1-4 contain the respective component contents

Content of Components (at%)	Al	Co	Cr	Cu	Ni
						Example 1 (x = 0.6)	11.5	19.2	19.2	19.2	30.9
Example 2 (x = 0.8)	14.3	17.9	17.9	17.9	32
						Example 3 (x = 1.0)	16.7	16.7	16.7	16.7	33.2
Example 4 (x = 1.2)	18.7	15.6	15.6	15.6	34.5

Example 1

Step 1: the high-purity metal raw material is placed in a 99.5% absolute ethyl alcohol solution to be subjected to ultrasonic cleaning by using an ultrasonic cleaning machine and is dried by using a vacuum drying oven.

Step 2: the respective raw materials were weighed in accordance with the elemental component contents of example 1 listed in table 1 using an electronic balance with an accuracy of 0.001 g.

And step 3: and (3) sequentially putting the raw materials of Al, cu, ni, co and Cr into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the step 2. And a pure titanium block is placed in a crucible B of the vacuum smelting furnace.

And 4, step 4: vacuumizing the vacuum arc melting furnace to 5 x 10 ^-3 And filling high-purity argon into the furnace chamber below Pa. The pure titanium block placed in step 3 was melted in crucible B using an arc with an arc current of 100A for a duration of 20s. Then, the samples in the crucible A are smelted, the current ranges from 150A to 200A, and smelting is repeated for at least 5 times for each sample.

And 5: applying a single-roller rapid solidification device, wherein the roller rotating speed is 18m/s, and carrying out treatment on the Al obtained in the step 4 _0.6 CoCrCuNi _1.6 The eutectic high-entropy alloy button ingot is prepared into an alloy solder foil strip with the thickness of about 60 mu m.

Example 2

And 2, step: the respective raw materials were weighed in accordance with the elemental component contents of example 2 listed in table 1 using an electronic balance with an accuracy of 0.001 g.

And 3, step 3: and (3) sequentially putting the raw materials of Al, cu, ni, co and Cr into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the step 2. And a pure titanium block is placed in a crucible B of the vacuum smelting furnace.

And 4, step 4: vacuum pumping the vacuum arc melting furnace to 5 x 10 ^-3 And (5) filling high-purity argon into the furnace chamber below Pa. The pure titanium block placed in step 3 was melted in crucible B using an arc with an arc current of 100A for a duration of 20s. Then melting the sample in the crucible A, the current range is 150A-200A, eachThe melting of the sample was repeated at least 5 times.

And 5: applying a single-roller rapid solidification device, wherein the roller rotating speed is 20m/s, and carrying out the step 4 to obtain Al _0.8 CoCrCuNi _1.8 The eutectic high-entropy alloy button ingot is prepared into an alloy solder foil strip with the thickness of about 80 mu m.

Example 3

Step 2: the respective raw materials were weighed in accordance with the elemental component contents of example 3 listed in table 1 using an electronic balance with an accuracy of 0.001 g.

And 3, step 3: and (3) sequentially putting the raw materials of Al, cu, ni, co and Cr into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the raw materials in the step 2. And a pure titanium block is placed in a crucible B of the vacuum smelting furnace.

And 4, step 4: vacuum pumping the vacuum arc melting furnace to 5 x 10 ^-3 And (5) filling high-purity argon into the furnace chamber below Pa. The pure titanium block placed in step 3 was melted in crucible B using an arc with an arc current of 100A for a duration of 20s. Then, the samples in the crucible A are smelted, the current ranges from 150A to 200A, and smelting is repeated for at least 5 times for each sample.

And 5: applying a single-roller rapid solidification device, wherein the roller rotating speed is 20m/s, and carrying out treatment on the Al obtained in the step 4 _1.0 CoCrCuNi _2.0 The eutectic high-entropy alloy button ingot is prepared into an alloy solder foil strip, and the thickness of the alloy solder foil strip is about 80 mu m.

As shown in fig. 1, 2 and 3. An XRD diffraction pattern shows that the prepared high-entropy alloy is of an FCC + BCC two-phase solid solution structure, and the Cu-rich phase can improve the plasticity of the high-entropy alloy; the melting point of the obtained brazing filler metal is about 1030 ℃; the high-entropy alloy solder is good in forming and free of obvious casting defects in the structure.

Example 4

Step 2: the respective raw materials were weighed in accordance with the elemental component contents of example 4 listed in table 1 using an electronic balance with an accuracy of 0.001 g.

And step 3: and (3) sequentially putting the raw materials of Al, cu, ni, co and Cr into a crucible A of a vacuum arc melting furnace according to the sequence of melting points from low to high in the raw materials in the step 2. And a pure titanium block is placed in a crucible B of the vacuum smelting furnace.

And 5: using a single-roller rapid solidification device, wherein the roller rotating speed is 24m/s, and carrying out the step 4 to obtain Al _1.2 CoCrCuNi _2.2 The eutectic high-entropy alloy button ingot is prepared into an alloy solder foil strip with the thickness of about 70 mu m.

The high-entropy brazing filler metal prepared by the method is subjected to vacuum brazing of TC4 titanium alloy and 316L stainless steel, and the shear strength of a joint is tested according to a strength test method of a brazed joint GB/T11363-2008. As can be seen from the table 2, the eutectic high-entropy alloy solder component provided by the invention can realize reliable connection of TC4 titanium alloy and 316L stainless steel, the welding effect is stable, and the average maximum shear strength of a welded joint can reach more than 200 MPa.

TABLE 2 average shear strength after vacuum brazing of different high-entropy alloy solders

Numbering	Average shear strength
		Example 1	≥215MPa
Practice ofExample 2	≥238MPa
		Example 3	≥260MPa
Example 4	≥220MPa

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An eutectic high-entropy alloy solder for brazing titanium, titanium alloy and stainless steel is characterized in that the solder is Al _x CoCrCuNi _1+x The eutectic high-entropy alloy solder is prepared by pseudo-binary combination of AlNi and CoCrNi, and is added with a Cu element to slowly release stress between two components of AlNi-CoCrNi, wherein the solder structure is a two-phase solid solution structure;

the material consists of the following raw materials in atomic percentage:

11.5-18.7% of Al, 15.6-19.2% of Co, 15.6-19.2% of Cr, 15.6-19.2% of Cu and 30.9-34.5% of Ni, wherein the sum of the atomic percentages of the components is 100%, wherein x represents the molar ratio of Al to Co, cr and Cu elements, namely the molar ratio of Al to Co to Cr to Cu to Ni is x: 1.

2. An eutectic high entropy alloy solder for brazing titanium and titanium alloys with stainless steel according to claim 1, characterized in that the Al, co, cr, cu and Ni are pure metal particles with a purity of 99.99%.