CN106435419B - Preparation method of AZ91D alloy with ultrafine-grained solidification structure - Google Patents

Preparation method of AZ91D alloy with ultrafine-grained solidification structure Download PDF

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CN106435419B
CN106435419B CN201610901581.5A CN201610901581A CN106435419B CN 106435419 B CN106435419 B CN 106435419B CN 201610901581 A CN201610901581 A CN 201610901581A CN 106435419 B CN106435419 B CN 106435419B
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solidification
alloy
az91d alloy
az91d
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CN106435419A (en
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王林
林小娉
樊志斌
李婵
李传会
陈思
苗琳坤
刘陈
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Northeastern University Qinhuangdao Branch
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • B22D27/11—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of mechanical pressing devices
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons

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Abstract

The invention discloses a preparation method of AZ91D alloy with an ultrafine crystal solidification structure, which comprises the following steps of (1) preprocessing, namely taking an AZ91D alloy cast ingot for diffusion annealing and cutting the ingot into a sample, and (2) performing high-pressure solidification treatment on the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment to obtain the AZ91D alloy with the ultrafine crystal solidification structure, wherein the obtained product has higher strength and good plasticity, in the AZ91D alloy prepared by the method, the size of Mg matrix grains is reduced to 10 mu m from 350 mu m of the original alloy, and dendritic crystal structures are remarkably refined, and β -Mg is used for refining the dendritic crystal structures17Al12The phases are connected into a net shape from the original alloy in a skeleton shape and are distributed among dendrites, and the net shape is converted into a nano-grade particle shape and is distributed among the dendrites in a dispersing way.

Description

Preparation method of AZ91D alloy with ultrafine-grained solidification structure
Technical Field
The invention relates to a preparation method of AZ91D alloy with an ultrafine grain solidification structure, and particularly belongs to the technical field of alloy preparation.
Background
The magnesium alloy has the characteristics of excellent electrical conductivity, thermal conductivity, electromagnetic shielding performance, high specific strength, specific stiffness, shock absorption and the like, is the lightest metal structure material in practical application at present, and has wide application prospect in the industries of aerospace, automobiles, 3C (computer, communication and consumer electronics) and the like. However, magnesium alloys have limited further industrial applications due to problems of low strength, poor toughness, difficult plastic working, poor high temperature creep properties, etc. Therefore, the improvement of the mechanical properties of the magnesium alloy through various preparation technologies and the expansion of the application range of the magnesium alloy are important points in the research and development of the technical field of the magnesium alloy.
The casting structure of the alloy is relatively coarse whether sand casting, metal mold casting or die casting with faster solidification, and the main strengthening phase β -Mg is disclosed17Al12Most of the materials are in a skeleton shape and are connected into a net shape and distributed among α -Mg dendrites, not only β -Mg17Al12The strengthening effect of the phase can not be fully exerted, and the mechanical property of the cast AZ91D alloy can be reduced, so that the mechanical property of the AZ91D alloy is further improved, the application range of the AZ91D alloy is expanded, the solidification structure of the AZ91D alloy is refined, and β -Mg is improved17Al12The morphology and distribution of the phases is very important.
At present, the main refining measures adopted for casting AZ91D alloy in the domestic and foreign solidification process are a melt superheating method, a solvent treatment method, an alloy element addition method, a melt stirring method and the like, but the refining effect is limited, the average grain size is difficult to reach below hundred microns, and β -Mg is difficult to reach17Al12The distribution and morphology of the phases is not substantially improved. Therefore, it is necessary to develop a method for preparing the AZ91D alloy having an ultra-fine grain solidification structure.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a preparation method of AZ91D alloy with ultra-fine grain solidification structure, and the obtained product has higher strength and good plasticity.
In order to achieve the above object, the present invention adopts the following technical solutions:
a preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and cutting the cast ingot into a sample;
(2) sample high-pressure solidification treatment: and (3) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment to obtain the sample.
Specifically, the preparation method of the AZ91D alloy with the ultrafine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to the solidification pressure, rapidly heating to the preset temperature, then carrying out heat preservation and pressure maintaining at the temperature, then stopping heating, naturally cooling to room temperature under the pressure maintaining condition, and releasing the pressure to obtain the product.
In the preparation method of the AZ91D alloy with the ultrafine grain solidification structure, in the step (2), the solidification pressure is 2-4 GPa.
In the preparation method of the AZ91D alloy with the ultrafine grain solidification structure, in the step (2), the preset temperature is 850-950 ℃.
In the preparation method of the AZ91D alloy with the ultrafine grain solidification structure, in the step (2), the heat preservation and pressure maintaining time is 15-20 min.
In the preparation method of the AZ91D alloy with the ultrafine grain solidification structure, in the step (1), the size of the sample is 6-12 mm in diameter and 6mm in length. The larger the diameter, the slower the cooling rate, and the larger the average grain size of the solidification structure.
In order to ensure the scientificity, reasonability and effectiveness of the scheme of the invention, the inventor carries out a series of experiments.
First, sample preparation
A cast AZ91D alloy ingot was subjected to diffusion annealing, and preferably wire-cut into specimens 6mm in diameter and 6mm in length. The larger the specimen size, the slower the cooling rate, the larger the grain size, and the lower the performance. Wherein the AZ91D alloy ingot comprises the following components (mass fraction): al 9.163, Zn 0.538, Mn 0.218, and the balance Mg. A CS-1B type high-pressure cubic press is adopted for high-pressure experiments. FIG. 1 is a schematic view of a high pressure cubic-anvil sample graphite assembly sleeve. As can be seen from the figure, the graphite assembly sleeve comprises a boron nitride crucible and a graphite crucible arranged outside the boron nitride crucible, the graphite crucible is integrally installed in a WC pressurizing column, pyrophyllite is arranged on two symmetrical sides of the WC pressurizing column, and hammers are arranged on six sides of the graphite assembly sleeve. And placing the sample in a boron nitride crucible in a graphite assembly sleeve, then placing the assembled graphite assembly sleeve in a cavity position of a high-pressure six-surface top, and starting a high-pressure solidification experiment after aligning the hammer head. Setting the solidification pressure and the preset temperature, raising the pressure to the solidification pressure of 2-4 GPa, simultaneously rapidly heating to the preset temperature of 850-950 ℃, then carrying out heat preservation and pressure maintaining at the temperature for 15-20 min, then stopping heating, cooling to the room temperature under the pressure maintaining condition, and releasing the pressure to obtain the material.
Second, experimental results and analysis
1. Observation with an optical microscope
The experimental alloy microstructure is observed and analyzed by using an Axio Scope A1 pol type Optical Microscope (OM), as shown in FIG. 2, FIG. 2 is respectively an AZ91D alloy ingot structure and an OM image of the AZ91D alloy with the ultrafine crystal solidification structure, as shown in FIG. 2A, the AZ91D alloy ingot structure is a coarse dendritic crystal structure, the average grain size is about 350 μm, FIG. 2B is an AZ91D alloy with the ultrafine crystal solidification structure obtained after the heating and melting temperature is 850 ℃ and the heat preservation is carried out for 20min under the action of 4GPa high pressure, the comparison of FIG. 2A shows that the maximum characteristic of the high pressure solidification structure is that the number of crystal nuclei is greatly increased on a unit area, the second is α -Mg crystal is an isometric crystal with a shorter arm length, the average grain size is only about 10 μm, FIG. 2C and FIG. 2D are respectively 4GPa high pressure action, the crystal nuclei obtained under the conditions of heating and melting at 900 ℃ and 950 ℃ are obviously influenced by overheating solidification, the overheating solidification of the melt is also shown in the comparison of the AZ91D B, and the overheating solidification structure is obviously influenced by one of the overheating solidification of the melt under the overheating solidification under the action of the overheating growth of the melt under the overheating growth of the melt.
2. Observation by scanning electron microscope
The microstructure of the experimental alloy was observed and analyzed by an LEO JSM 5400 Scanning Electron Microscope (SEM), as shown in FIG. 3, FIGS. 3-A and 3-B are SEM images of AZ91D alloy ingot at different magnifications, and it can be seen that the AZ91D alloy ingot structure is formed by primary alpha-Mg + (alpha-Mg + β -Mg)17Al12) Eutectic structure and white intermediate β -Mg formed by rich aluminum between dendrites17Al12Composition of eutectic β -Mg17Al12The phases are connected into a skeleton shape and are distributed among alpha-Mg dendrites, and an SEM image of an AZ91D alloy with an ultrafine grain solidification structure is obtained after heating and melting at 850 ℃ under the action of 4GPa high pressure is shown in figures 3-C and 3-D under different magnifications, compared with an AZ91D alloy cast structure in figures 3-A and 3-B, the AZ91D alloy with the ultrafine grain solidification structure is characterized in that a second phase is distributed on a matrix in a granular dispersion mode under the action of low power (figure 3-C), a granular second phase with the size close to nm level under the action of high power (figure 3-D) is distributed on grain boundaries in a uniform dispersion mode, EDS inspection results show that the atomic percentages of Mg, Al and Zn in the granular second phase are respectively 58.34%, 36.12% and 5.54%, and the solubilities of Al and Zn in the matrix are respectively 3.50% (mass fraction, lower phase) and 0.3635%, and compared with the original AZ 91- β alloy in the solidification structure, the AZ 91- β alloy in the cast structure is shown in the original β17Al12More Zn (original 2.48%) was dissolved in the matrix and more Al (original 2.46%) was dissolved in the matrix, in combination with the XRD spectrum shown in FIG. 4, the high pressure solidified AZ91D alloy structure was still formed from an alpha-Mg matrix and β -Mg17Al12Phase composition.
3. X-ray diffraction analysis
Performing phase analysis by using 2500/PC type X-ray diffractometer, scanning step length is 0.3 °, and XRD diffraction spectrum is obtained by measuring between 20 ° and 90 ° (2 θ). As shown in FIG. 4, half peak width of alpha-Mg after high pressure solidification clearly observed by XRD spectrum shown in FIG. 4 is widened, β -Mg17Al12The phase diffraction peak has the tendency of steamed bread peak, which further proves that not only alpha-Mg matrix is obviously refined, but also alpha-Mg matrix is divided intoβ -Mg between branchy crystal17Al12The phase morphology and distribution are also greatly improved, β -Mg17Al12The phases are changed from 'skeleton-shaped' in AZ91D alloy ingot into nm-grade particles which are uniformly dispersed and distributed on grain boundaries.
4. Compression performance
The WDW3100 microcomputer controlled electronic universal tester is used for room temperature compression experiment, strain rate
Figure BDA0001131787710000031
Is 0.001s-1And a computerized data recorder attached to the universal tester automatically collects data such as stress, strain and the like in the compression process. The results are shown in FIG. 5. As can be seen from the figure, the compression strength of the AZ91D alloy cast ingot is 263MPa, and the cross-sectional expansion rate is 14%; the AZ91D alloy solidified under the action of high pressure of 4GPa has the compressive strength as high as 402MPa and the section expansion rate of 20 percent. The high-pressure solidification not only greatly improves the strength of the magnesium alloy, but also improves the plasticity of the magnesium alloy to a certain extent.
FIG. 6 is a SEM image of fracture morphology of AZ91D alloy with ultrafine grained solidification structure. The fracture surface (fracture) of the AZ91D alloy cast ingot after compression fracture and the compression axis form about 45 degrees, and the fracture surface is smooth and bright; as can be seen from the SEM image of the fracture shown in fig. 6a, the fracture occurs along a specific crystallographic plane (cleavage plane), the cleavage plane is large and smooth, the cleavage step is relatively flat, and typical cleavage fracture occurs. As can be seen from fig. 6b, the compressive fracture cleavage plane area of the alloy with the ultrafine grain solidification structure AZ91D obtained by high-pressure solidification is obviously reduced, the cleavage step height is obviously reduced, and the cleavage steps are connected into slopes and uneven in undulation by smaller steps; the upper and lower cleavage step attachment areas have a tear-away band, and further enlargement (fig. 6c) clearly shows the presence of shear dimples at both ends of the tear-away band. The compression fracture mode of the AZ91D alloy with the ultra-fine grain solidification structure solidified under high pressure is shown to be changed compared with the AZ91D alloy cast ingot, and the fracture mode is closer to quasi-cleavage fracture.
In order to control the solidification process of metals or alloys, the conventional method is to change the solidification structure by adjusting the chemical composition and temperature, while another thermodynamic parameter, pressure, affecting the solidification process is usually ignored. Pressure, temperature and chemical composition are important thermodynamic variables, which also have important influence on the solidification process of the metal or the alloy, and particularly, when the pressure reaches the GPa grade, the thermodynamics and the kinetics of the solidification process of the metal or the alloy are greatly changed. According to the existing high-pressure solidification theory, the pressure always reduces the nucleation activation energy and increases the nucleation rate; the atomic diffusion is inhibited, so that the atomic diffusion activation energy is increased, the crystal growth activation energy is increased, and the crystal growth rate is reduced.
The solidification pressure has great influence on the obtaining of superfine dendritic crystal structure, when solidification is carried out under the action of high pressure of GPa, the diffusion coefficient of solute is exponentially reduced, a solute atom enrichment area is easily formed in a matrix, the crystal nucleation rate is greatly increased due to the existence of heterogeneous nucleation mass points in the crystal, and the growth speed of the crystal is inhibited, so that the dendritic crystal structure of the alloy is obviously refined when solidification is carried out under ultrahigh pressure, the heating temperature, namely the superheat degree of the melt, has great influence on the solidification structure, the overhigh heating temperature can not only coarsen the solidification structure, but also lead the crystal growth to be changed from spherical crystal to dendritic crystal, and the autogenous nano-scale granular β -Mg17Al12The formation of the phase has an optimal high-pressure solidification process parameter, and the excessive solidification pressure can promote more Al to be dissolved into the Mg matrix, so that the granular β -Mg17Al12The number of phases will decrease and the solidification pressure is too low, β -Mg17Al12The meeting still takes the shape of "skeleton" and is connected into a net or semi-continuous distribution among dendrites.
In the present invention, the AZ91D alloy having an ultrafine grain solidification structure is characterized by an as-cast structure consisting of nano-sized particles β -Mg17Al12The alloy consists of α -Mg matrix, α -Mg is spherical crystal, the average size of crystal grains is about 10 mu m, the solid solution amount of Al in α -Mg matrix is up to 3.50 wt% and is far higher than 2.48 wt% of the original AZ91D alloy, β -Mg17Al12The phase is granular, the size is nm grade, the phase is dispersedly distributed among α -Mg dendrites, β -Mg17Al12The volume percentage of the phase in the form of particles is about 8%.
The strength of the material is a mechanical property index which is extremely sensitive to components and tissue structures. As can be seen from FIGS. 2 and 3, the AZ91D alloy with a coarse primary structure (grain size 350 μm) was subjected to high-pressure solidification at 850 ℃ and 4GPa to reduce the grain size to 10 μm. According to the Hall-Petch formula (sigma)s＝σ0+kd-1/2In the formula: sigma is the yield strength of the alloy; sigma0And k is a constant related to the crystal type; d is the grain size), the yield strength of the alloy is inversely proportional to the square root of the grain size. The Hall-Petch constant k value of the magnesium alloy is large (k is 280-320 MPa.mu.m)-1/2) Secondly, after high-pressure solidification, the solubility of Al in a matrix is improved to 3.50 percent from 2.48 percent in the original alloy, and solid solution strengthening also contributes to the improvement of the alloy strength17Al12The phase is changed from the reticular shape of the fracture matrix into the nm-grade granular dispersion distribution, so that not only can the function of the matrix be fully exerted, but also the granular β -Mg with higher hardness is dispersed and distributed17Al12The phase can also play a certain role in dispersion strengthening. Therefore, the strength of the magnesium alloy solidified under high pressure is greatly improved under the combined action of fine crystal strengthening, dispersion strengthening and solid solution strengthening, and is improved from 263MPa of the original AZ91D alloy ingot to 402MPa by nearly 50%.
The AZ91D alloy with ultra-fine grain solidification structure solidified under high pressure has improved strength and plasticity, the high pressure solidification makes the AZ91D alloy grain size refined to 10 μm, along with the refinement of the grain size, the proportion of grain boundary is increased, the coordination of grain boundary is obvious, the material deformation is more uniform, the compression strength and plasticity of the material are improved, in addition, the improvement of the plasticity of the AZ91D alloy with ultra-fine grain solidification structure has great relation with the shape and distribution of the second phase, β -Mg in the original AZ91D alloy cast structure17Al12The phase is distributed among dendrites in a continuous net shape to surround the matrix phase, and the alloy is easy to crack along a continuous second phase; and is solidified under high pressurePost β -Mg17Al12The phase is dispersed and distributed on the grain boundary in nm-level particles, which may also be one of the reasons for improving the plasticity to some extent.
The invention has the beneficial effects that the AZ91D alloy with the ultrafine grain solidification structure is prepared by solidifying an AZ91D alloy cast ingot under the action of high GPa pressure, and obtaining the required alloy material by controlling the solidification pressure, the heating temperature and the solidification cooling rate, and the AZ91D alloy with the ultrafine grain solidification structure has higher mechanical property, on one hand, the grain size of the Mg matrix is reduced to 10 mu m from 350 mu m of the original alloy, and the dendritic structure is remarkably refined, on the other hand, β -Mg17Al12The phases are connected into a net shape from the original alloy in a skeleton shape and are converted into nano-scale particles which are dispersed and distributed among dendrites; furthermore, the amount of solid solution Al of the Mg matrix is greatly increased from 2.4 wt% of the original alloy to 3.50 wt% under high pressure, which is increased by 24%. Particularly, the AZ91D alloy prepared under the heating conditions of 4GPa of solidification pressure and 850 ℃ of heating temperature has the compression strength of 402MPa at room temperature and the section expansion rate of 20 percent. The high-pressure solidified AZ91D alloy is shown to have higher strength and good plasticity.
Drawings
FIG. 1 is a schematic view of a high pressure cubic-anvil sample graphite assembly sleeve;
FIG. 2 is an optical microscope photograph of an AZ91D alloy having an ultrafine grained solidification structure according to the present invention;
FIG. 3 is an SEM image of an AZ91D alloy having an ultrafine grained solidification structure;
FIG. 4 is an XRD pattern of an AZ91D alloy having an ultra-fine grained solidification structure;
FIG. 5 is a stress-strain plot of AZ91D alloy with ultra-fine grained solidification structure;
FIG. 6 is a fracture morphology SEM image of AZ91D alloy with ultra-fine grained solidification structure;
the meaning of the reference symbols in the figures: FIG. 1: 1-pyrophyllite, 2-graphite crucible, 3-WC pressurizing column, 4-boron nitride crucible, 5-sample, 6-pressing hammer; FIG. 2: A-AZ91D alloy ingot, B-4GPa, 850 ℃, C-4GPa, 900 ℃, D-4GPa and 950 ℃; FIG. 3: A-AZ91D alloy ingot is amplified by 100 times, B-AZ91D alloy ingot is amplified by 500 times, C-4GPa and 850 ℃ are amplified by 100 times, D-4GPa and 850 ℃ are amplified by 500 times; fig. 4 and 5: a-4GPa, 850 ℃ and b-AZ91D alloy ingot casting; FIG. 6: the magnification of a-AZ91D alloy ingot is 200 times, b-the invention AZ91D alloy is 200 times, c-the invention AZ91D alloy is 500 times.
Detailed Description
The invention is further described with reference to specific examples.
Example 1
A preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample with the diameter of 10mm and the length of 6 mm;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to the solidification pressure of 2GPa, simultaneously rapidly heating to the preset temperature of 950 ℃, carrying out heat preservation and pressure maintaining at the temperature, then stopping heating for 18min, naturally cooling to room temperature under the pressure maintaining condition, and relieving the pressure to obtain the product.
Example 2
A preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample with the diameter of 12mm and the length of 6 mm;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to the solidification pressure of 3GPa, simultaneously rapidly heating to the preset temperature of 900 ℃, carrying out heat preservation and pressure maintaining at the temperature, then stopping heating for 20min, naturally cooling to room temperature under the pressure maintaining condition, and relieving the pressure to obtain the product.
Example 3
A preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample with the diameter of 6mm and the length of 6 mm;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to 4GPa, rapidly heating to 850 ℃ at the preset temperature, then carrying out heat preservation and pressure maintaining at the temperature, then stopping heating for 15min, naturally cooling to room temperature under the pressure maintaining condition, and relieving the pressure to obtain the product.
Example 4
A preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample with the diameter of 9mm and the length of 6 mm;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to 4GPa, rapidly heating to 900 ℃, keeping the temperature and pressure at the temperature, stopping heating for 16min, naturally cooling to room temperature under the pressure keeping condition, and relieving the pressure to obtain the product.
Example 5
A preparation method of AZ91D alloy with ultra-fine grain solidification structure comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample with the diameter of 8mm and the length of 6 mm;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification treatment, setting solidification pressure and preset temperature, raising the pressure to the solidification pressure of 2.5GPa, simultaneously rapidly heating to the preset temperature of 930 ℃, carrying out heat preservation and pressure maintaining at the temperature, then stopping heating for 19min, naturally cooling to room temperature under the pressure maintaining condition, and relieving the pressure to obtain the product.

Claims (2)

1. A preparation method of AZ91D alloy with ultra-fine grain solidification structure is characterized by comprising the following steps: the method comprises the following steps:
(1) pretreatment: carrying out diffusion annealing on the AZ91D alloy cast ingot, and carrying out wire cutting to obtain a sample;
(2) sample high-pressure solidification treatment: and (2) placing the sample in the step (1) in a CS-1B type high-pressure cubic press for high-pressure solidification, setting the solidification pressure to be 4GPa and the preset temperature to be 850 ℃, raising the pressure to the solidification pressure, simultaneously rapidly heating to the preset temperature, keeping the temperature and the pressure for 15-20 min at the temperature, then stopping heating, naturally cooling to room temperature under the pressure keeping condition, and releasing the pressure to obtain the product.
2. The method for preparing an AZ91D alloy having an ultrafine grained solidification structure according to claim 1, wherein: in the step (1), the size of the sample is 6mm in diameter and 6mm in length.
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