CN110666447B - Magnesium alloy material with mixed crystal structure and preparation method thereof - Google Patents

Magnesium alloy material with mixed crystal structure and preparation method thereof Download PDF

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CN110666447B
CN110666447B CN201910822560.8A CN201910822560A CN110666447B CN 110666447 B CN110666447 B CN 110666447B CN 201910822560 A CN201910822560 A CN 201910822560A CN 110666447 B CN110666447 B CN 110666447B
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magnesium alloy
blind holes
crystal structure
stirring
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CN110666447A (en
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王文
强菲
韩鹏
王快社
乔柯
张婷
刘强
陈善勇
刘志浩
王智
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Xian University of Architecture and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
    • B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
    • B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
    • B23K20/1245—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding characterised by the apparatus
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • 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
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/08—Non-ferrous metals or alloys
    • B23K2103/15—Magnesium or alloys thereof

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Abstract

The invention discloses a magnesium alloy material with a mixed crystal structure and a preparation method thereof, which comprises the steps of processing a plurality of blind holes on the surface of a magnesium alloy plate, adding powder A into the blind holes, carrying out friction stir processing on the magnesium alloy plate filled with the powder A by adopting a friction stir processing device at the temperature of-196-26 ℃, and carrying out heat treatment on the processed plate to obtain the magnesium alloy material. The powder A is mixed powder of one or more of vanadium nitride, silicon carbide or titanium diboride. The preparation method introduces the combination of the stirring friction processing process of controlling the cooling mode, the addition of the second phase particles and the subsequent heat treatment process to realize the preparation of the mixed crystal structure material. The method is convenient to operate, and the prepared mixed crystal structure material has excellent comprehensive mechanical properties of strength and plasticity.

Description

Magnesium alloy material with mixed crystal structure and preparation method thereof
Technical Field
The invention belongs to the field of metal material processing and preparation, and particularly relates to a magnesium alloy material with a mixed crystal structure and a preparation method thereof.
Background
In recent years, magnesium alloy has been widely used in the fields of automobiles, aerospace, medical instruments and the like, and is known as a green engineering material in the 21 st century. It is worth noting that the magnesium alloy is similar to human skeleton in physical properties such as density, elastic modulus and the like, so that the magnesium alloy is the most potential medical degradable metal material, but the defects of low strength and poor plasticity severely restrict the development and application of the magnesium alloy.
At present, the strength and plasticity of magnesium alloy are improved by adopting a severe plastic deformation technology to realize grain refinement, but the technology can cause great loss of plasticity while improving the strength. According to the theory of fine grain strengthening, there is a Hall-Peltier relationship between the yield strength and the grain size of the material: (
Figure BDA0002187983530000011
σyRepresenting the yield strength, σ, of the material0Representing the frictional resistance of the lattice generated when a single dislocation is moved, K being a constant associated with the material, and d being the grain diameter), the smaller the grain size, the higher the strength of the material. But the plasticity of the material is increasingly poor while the strength is improved. This is because the fine crystals have less space to accommodate mobile dislocations, resulting in a reduced work hardening capability of the material. Therefore, researchers propose a 'mixed crystal structure' to improve the strength and the plasticity of the magnesium alloy material at the same time, namely, coarse crystals are used for providing good plasticity for the material, and fine crystals are used for providing good strength for the material. The microstructure with the coarse grains and the fine grains which are uniformly mixed and matched with each other has great effect on improving the strength and the plasticity of the magnesium alloy material. However, how to prepare the magnesium alloy material with the mixed crystal structure is still in the exploration stage at present, and no specific preparation technology is found.
Disclosure of Invention
Aiming at the blank of the preparation technology of the magnesium alloy with the mixed crystal structure, the invention provides a magnesium alloy material with the mixed crystal structure and a preparation method thereof.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a magnesium alloy material with a mixed crystal structure and a preparation method thereof are provided, which comprises the steps of processing a plurality of blind holes on the surface of a magnesium alloy plate, adding powder A into the blind holes, carrying out friction stir processing on the magnesium alloy plate filled with the powder A by adopting a friction stir processing device at the temperature of-196-26 ℃, and carrying out heat treatment on the processed plate to obtain the magnesium alloy material, wherein the powder A is Vanadium Nitride (VN), silicon carbide (SiC) or titanium diboride (TiB)2) One or more kinds of mixed powder.
Furthermore, the blind holes are cylindrical, the diameter D of each blind hole is 1-3 mm, the distance a between every two rows of blind holes is 4-6 mm, and the distance b between every two rows of blind holes is 7-9 mm.
Further, the stirring head used in the friction stir processing process comprises a shaft shoulder and a stirring pin, wherein the shaft shoulder and the stirring pin are both cylindrical.
Further, the thickness of the magnesium alloy plate is 1-10 mm, and the diameter of a shaft shoulder of the stirring head is 8-30 mm; the stirring pin diameter is greater than blind hole diameter 0.5 ~ 2mm, and the stirring pin diameter is 1.5 ~ 5mm promptly, and stirring pin length is less than magnesium alloy panel thickness 0.2 ~ 0.5mm, and stirring pin length is 0.8 ~ 9.5mm promptly, blind hole degree of depth h is less than stirring pin length 0 ~ 1mm, and the blind hole degree of depth is 0.8 ~ 8.5mm promptly.
Further, the friction stir processing parameters are as follows: the rotating speed of the stirring head is 600-1500 rpm, the advancing speed is 20-40 mm/min, and the pressing amount of the shaft shoulder is 0.1-0.3 mm.
Further, the heat treatment temperature is 0.35Tm～0.45TmWherein, TmThe melting point of the material is shown, and the heat preservation time is 10-30 min.
Further, the method specifically comprises the following steps:
processing a plurality of blind holes in parallel and in multiple rows on the surface of the magnesium alloy plate, adding vanadium nitride into the blind holes, performing friction stir processing on the magnesium alloy plate filled with the vanadium nitride by using a friction stir processing device at the temperature of 5-26 ℃, and performing heat treatment on the processed plate to obtain the magnesium alloy plate.
For a magnesium alloy plate with the thickness of 4mm, the diameter D of blind holes is 2mm, the distance a between every two rows of blind holes is 5mm, the distance b between every two rows of blind holes is 8mm, the depth h of the blind holes is 3.7mm, the diameter of a stirring pin is 4mm, the length of the stirring pin is 3.8mm, the diameter of a shaft shoulder of a stirring head is 16mm, the pressing amount of the shaft shoulder is 0.2mm, the rotating speed of the stirring head is 750rpm, the advancing speed is 30mm/min, the heat treatment temperature is 228 ℃, and the heat preservation time is 20 min.
Further, the method specifically comprises the following steps:
processing a plurality of blind holes in parallel and in multiple rows on the surface of the magnesium alloy plate, adding vanadium nitride into the blind holes, performing friction stir processing on the magnesium alloy plate filled with the vanadium nitride by using a friction stir processing device at the temperature of-196-0 ℃, and performing heat treatment on the processed plate to obtain the magnesium alloy plate.
For a magnesium alloy plate with the thickness of 5mm, the diameter D of blind holes is 3mm, the distance a between every two rows of blind holes is 6mm, the distance b between every two rows of blind holes is 9mm, the depth h of the blind holes is 4.7mm, the diameter of a stirring pin is 4mm, the length of the stirring pin is 4.8mm, the diameter of a shaft shoulder of a stirring head is 16mm, the pressing amount of the shaft shoulder is 0.2mm, the rotating speed of the stirring head is 850rpm, the advancing speed is 35mm/min, the heat treatment temperature is 228 ℃, and the heat preservation time is 20 min.
The magnesium alloy material with the mixed crystal structure is prepared by any one of the preparation methods of the mixed crystal structure material, and the product of strength and elongation of the magnesium alloy material with the mixed crystal structure is 4446.75-4764.42 MPa.
The invention has the following technical effects:
the preparation method of the invention combines the stirring friction processing process of controlling the cooling mode, the addition of the second phase particles and the subsequent heat treatment process to realize the preparation of the mixed crystal structure material. The method is convenient to operate, and the prepared mixed crystal structure material has excellent comprehensive mechanical properties of strength and plasticity.
Drawings
FIG. 1 is a view showing the arrangement of holes on the surface of a metal plate;
FIG. 2 is a schematic illustration of a friction stir processing line;
FIG. 3 is a schematic of a heat treatment process route;
FIG. 4 is a microstructure diagram of an AZ31 magnesium alloy material produced in example 1;
fig. 5 is a microstructure diagram of the AZ31 magnesium alloy material prepared in comparative example 1;
fig. 6 is a microstructure diagram of an AZ31 magnesium alloy material prepared in example 2;
fig. 7 is a microstructure diagram of the AZ31 magnesium alloy material prepared in comparative example 3.
Detailed Description
The principle of the invention is as follows: in the friction stir processing, the friction heat generated between the rotating stirring head and the workpiece surface is the main heat source in the processing process, and the friction heat is also the main reason for the recrystallization of the deformed crystal grains. However, excessive frictional heat easily coarsens the crystal grains. The invention controls the cooling mode in the friction stir processing process so as to inhibit the coarsening of the crystal grains. The purpose of cooling is to control the heat input for the friction stir process. In addition, on one hand, the addition of the second phase can effectively pin the grain boundary so as to refine the grains; on the other hand, the pinning resistance of the second phase particles pinned at the grain boundary is different, and a foundation is laid for the uneven growth of crystal grains in the subsequent heat treatment process. The effect of controlling the cooling mode and adding the second phase particles lays a foundation condition for uneven growth of crystal grains in the subsequent heat treatment process. Therefore, the invention utilizes the theory to prepare the magnesium alloy material with the mixed crystal structure through friction stir processing, and effectively improves the strength and plasticity of the magnesium alloy.
The blind hole is a through hole which is used for connecting the surface layer and the inner layer of the magnesium alloy plate and does not penetrate through the whole plate, is used for placing the powder A, and plays a role in refining grains in the recrystallization process of the magnesium alloy plate by taking the powder A as a second phase. For magnesium alloys, powder A may be Vanadium Nitride (VN), silicon carbide (SiC) or titanium diboride (TiB)2) And one or more of the above mixed powders.
Pretreatment of raw materials: selecting an AZ31 magnesium alloy plate as a raw material magnesium alloy plate, polishing the surface of AZ31 magnesium alloy by using sand paper to enable the surface roughness Ra to be less than or equal to 10 mu m, cleaning the surface by using acetone, removing oil stains, oxides and impurities on the surface, and drying. Then, the AZ31 magnesium alloy was fixed on a drill, and cylindrical blind holes in a plurality of rows were formed in the surface of the AZ31 magnesium alloy plate by using a drill, as shown in fig. 1. The diameter D of the blind holes is 1-3 mm, the distance a between every two rows of blind holes is 4-6 mm, the distance b between every two rows of blind holes is 7-9 mm, the depth h of the blind holes is smaller than the length of the stirring pin by 0-1 mm, and the depth of the blind holes is 0.8-8.5 mm.
The magnesium alloy plate filled with the second-phase particles is subjected to friction stir processing by adopting a friction stir processing device at the temperature of-196-26 ℃, the temperature during friction stir processing can be controlled by adopting circulating water or a circulating liquid nitrogen cooling device, the temperature of the circulating water cooling device can be controlled to be 5-26 ℃, and the temperature of the circulating liquid nitrogen cooling device can be controlled to be-196-0 ℃. The stirring head used in the friction stir processing process comprises a shaft shoulder and a stirring pin, and the shaft shoulder and the stirring pin are both cylindrical. The material of the stirring head is high-speed steel W18Cr4V, and the stirring pin is provided with threads. The diameter of the cylindrical shaft shoulder is 8-30 mm; the diameter of the cylindrical stirring pin is 1.5-5 mm, and the length of the cylindrical stirring pin is 0.8-9.5 mm.
Stirring friction processing parameters: the rotating speed of the stirring head is 600-1500 rpm, the advancing speed is 20-40 mm/min, and the pressing amount of the shaft shoulder is 0.1-0.3 mm.
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
Example 1:
according to the technical scheme, the invention provides a magnesium alloy material with a mixed crystal structure and a preparation method thereof.
A plurality of cylindrical blind holes in a plurality of rows are formed in the surface of a 200 multiplied by 180 multiplied by 4mm (length multiplied by width multiplied by thickness) AZ31 magnesium alloy plate in parallel, as shown in FIG. 1, the diameter D of the blind holes is 2mm, the distance a between the blind holes in each row is 5mm, the distance b between the blind holes in each row is 8mm, and the depth h of the blind holes is 3.7 mm. Filling Vanadium Nitride (VN) powder with the particle size of 1 mu m into the processed blind holes and compacting; and (2) carrying out friction stir processing on the magnesium alloy plate filled with the vanadium nitride by using a friction stir processing device at the temperature of 5-26 ℃, specifically, placing the magnesium alloy plate added with the vanadium nitride in a circulating water cooling device, wherein the temperature of the circulating water is 5-26 ℃, the height of the water surface of the circulating water cooling device is lower than that of the surface of the magnesium alloy plate, carrying out friction stir processing on the magnesium alloy plate filled with the vanadium nitride by using the friction stir processing device according to a processing route shown by an arrow in figure 2, and then carrying out heat treatment on the processed plate in a box-type resistance furnace according to a heat treatment process route shown in figure 3 to obtain the magnesium alloy material A1 with a mixed crystal structure.
The stirring head used in the friction stir processing process comprises a shaft shoulder and a stirring pin, the stirring head is made of high-speed steel W18Cr4V, and a cylindrical threaded stirring pin is adopted. The diameter of the shaft shoulder of the stirring head is 16mm, the diameter of the stirring needle is 4mm, the length of the stirring needle is 3.8mm, the pressing amount of the shaft shoulder is 0.2mm, the rotating speed of the stirring head is 750rpm, and the advancing speed is 30 mm/min. In the heat treatment process, the heating rate of the heat treatment furnace is 8 ℃/min, the heat treatment temperature T1 is 228 ℃, the heat preservation time is 20min, and then water cooling is carried out to the room temperature.
Comparative example 1:
this comparative example is the same as example 1 except that no blind hole was machined in the pre-treated AZ31 magnesium alloy sheet and no Vanadium Nitride (VN) powder was added. In a friction stir processing device with a circulating water cooling device, processing is carried out according to a friction stir processing route schematic diagram shown in figure 2, and the magnesium alloy-A2 with a uniform crystal structure is prepared.
Microstructure observation was performed on the AZ31 magnesium alloy sheets processed in example 1 and comparative example 1, as shown in fig. 4 and 5. Fig. 4 shows a microstructure of AZ31 magnesium alloy having a mixed crystal structure prepared in example 1, in which arrows indicate Vanadium Nitride (VN) particles. FIG. 5 shows the microstructure of AZ31 magnesium alloy prepared in comparative example 1, and no mixed crystal structure was found.
The AZ31 magnesium alloy material-a 1 prepared through the processing procedure of example 1 (addition of Vanadium Nitride (VN) powder to a metal plate → treatment of a circulating water cooling friction stir processing process → a heat treatment process) had coarse grains and fine grains uniformly distributed and exhibited an obvious mixed grain structure. The comparison with the microstructure (isometric crystal with uniform grain size) of the AZ31 magnesium alloy-A2 processed by the stirring friction processing technique with circulating water cooling only in the figure 5 shows that the AZ31 magnesium alloy material with the mixed crystal structure can be prepared by the scheme of the invention.
The mechanical property test result shows that the yield strength of the AZ31 magnesium alloy material A1 with the mixed crystal structure is 281.3MPa, the tensile strength is 302.5MPa, the elongation is 14.7 percent, and the product of strength and elongation is 4446.75 MPa. The yield strength of the AZ31 magnesium alloy plate-A2 without the mixed crystal structure is 290.4MPa, the tensile strength is 324.1MPa, the elongation is 3.8 percent, and the product of strength and elongation is 1231.58 MPa. Compared with the AZ31 magnesium alloy material with the homogeneous crystal structure, the AZ31 magnesium alloy material with the mixed crystal structure processed in the embodiment 1 has slightly reduced strength, greatly improved elongation and improved product of strength and elongation of 3215.17MPa, which shows that the invention obviously improves the strength and plasticity of the magnesium alloy material.
Comparative example 2
This comparative example is the same as example 1 except that the friction stir processing apparatus was not equipped with a circulating water cooling apparatus.
The process of comparative example 2 is: adding Vanadium Nitride (VN) powder to the metal plate → stirring friction processing technique treatment → heat treatment technique treatment. The cooling treatment is not carried out in the stirring and rubbing processing process, the mixed crystal structure characteristics in the microstructure of the obtained magnesium alloy material are not obvious, and the distribution of large and small crystal grains is not uniform, so that the performance of the magnesium alloy material is poor. This is because the heat input during friction stir processing is too large to coarsen the crystal grains, which in turn affects the performance.
Example 2
This example employs a circulating liquid nitrogen cooling device.
A250X 200X 5mm (length, width and thickness) AZ31 magnesium alloy plate is taken, a plurality of parallel columns of cylindrical blind holes are processed on the surface of the magnesium alloy plate, as shown in figure 1, the diameter D of the blind holes is 3mm, the distance a between every two adjacent rows of blind holes is 6mm, the distance b between every two adjacent rows of blind holes is 9mm, and the depth h of the blind holes is 4.7 mm. Vanadium Nitride (VN) powder having a particle diameter of 1 μm was filled into the above-mentioned processed blind holes and compacted. And (3) carrying out friction stir processing on the magnesium alloy plate filled with the vanadium nitride by adopting a friction stir processing device at the temperature of-196-0 ℃, specifically, placing the magnesium alloy plate added with the vanadium nitride in a circulating liquid nitrogen cooling device, wherein the temperature of circulating liquid nitrogen is-196-0 ℃, and the liquid nitrogen surface of the circulating liquid nitrogen cooling device is lower than the surface of the magnesium alloy plate. According to the processing route shown by an arrow in figure 2, stirring and rubbing processing is carried out on the magnesium alloy plate filled with vanadium nitride by using a stirring and rubbing processing device, and then the processed plate is subjected to heat treatment in a box-type resistance furnace according to the heat treatment process route shown in figure 3, so as to obtain the magnesium alloy material-B1 with a mixed crystal structure.
The stirring head used in the friction stir processing process comprises a shaft shoulder and a stirring pin, the stirring head is made of high-speed steel W18Cr4V, and a cylindrical threaded stirring pin is adopted. The diameter of the shaft shoulder of the stirring head is 16mm, the diameter of the stirring needle is 4mm, the length of the stirring needle is 4.8mm, the pressing amount of the shaft shoulder is 0.2mm, the rotating speed of the stirring head is 850rpm, and the advancing speed is 35 mm/min. In the heat treatment process, the heating rate of the heat treatment furnace is 8 ℃/min, the heat treatment temperature T1 is 228 ℃, the heat preservation time is 20min, and then water cooling is carried out to the room temperature.
Comparative example 3:
the comparative example is the same as the example 2, except that the AZ31 magnesium alloy plate after pretreatment is processed according to the schematic diagram of the friction stir processing route shown in the figure 2 in the friction stir processing device with a circulating liquid nitrogen cooling device without processing blind holes and adding Vanadium Nitride (VN) powder, and AZ31 magnesium alloy-B2 is obtained.
Microstructure observation was performed on the AZ31 magnesium alloy sheets processed in example 2 and comparative example 3, as shown in fig. 6 and 7. Fig. 6 is a microstructure diagram of a B1 of an AZ31 magnesium alloy material having a mixed crystal structure prepared in example 2. FIG. 7 is a microstructure diagram of AZ31 magnesium alloy-B2 prepared in comparative example 3, and no mixed crystal structure was found.
The AZ31 magnesium alloy material-B1 prepared through the processing procedure of example 2 (addition of Vanadium Nitride (VN) powder to a metal plate → processing of circulating liquid nitrogen cooling friction stir processing → heat treatment process) had uniform distribution of coarse grains and fine grains, and exhibited an obvious mixed grain structure. The result is obviously compared with the microstructure (isometric crystal with uniform grain size) of AZ31 magnesium alloy-B2 processed by the stirring friction processing technology with circulating liquid nitrogen cooling in the figure 7, and the AZ31 magnesium alloy material with the mixed crystal structure can be prepared by the scheme of the invention.
The mechanical property test result shows that the yield strength of the AZ31 magnesium alloy-B1 with the mixed crystal structure, which is prepared after being cooled by a circulating liquid nitrogen cooling device, is 282.4MPa, the tensile strength is 311.4MPa, the elongation is 15.3 percent, and the product of strength and elongation is 4764.42 MPa. The yield strength of the AZ31 magnesium alloy plate-B2 is 299.3MPa, the tensile strength is 331.5MPa, the elongation is 3.7 percent, and the product of strength and elongation is 1226.55 MPa. The product of strength and elongation is improved by 3537.87MPa, and the AZ31 magnesium alloy material B1 with the mixed crystal structure after being processed by the embodiment is obviously superior to the AZ31 magnesium alloy plate B2 with the uniform crystal structure in the aspect of strength and plasticity.
Comparative example 4
This comparative example is the same as example 2 except that the friction stir processing apparatus was not equipped with a circulating liquid nitrogen cooling apparatus.
The process of comparative example 4 was: adding Vanadium Nitride (VN) powder to the metal plate → stirring friction processing technique treatment → heat treatment technique treatment. The cooling treatment is not carried out in the stirring and rubbing processing process, the mixed crystal structure characteristics in the microstructure of the obtained magnesium alloy material are not obvious, and the distribution of large and small crystal grains is not uniform, so that the performance of the magnesium alloy material is poor. This is because the heat input during friction stir processing is too large to coarsen the crystal grains, which in turn affects the performance.
The above embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and the second phase may be silicon carbide (SiC) or titanium diboride (TiB)2) One or more of the powders are mixed to prepare the magnesium alloy material with a mixed crystal structure. All equivalent changes made by the claims of the present invention are intended to be included within the scope of the claims of the present invention.

Claims (3)

1. The preparation method of the magnesium alloy material with the mixed crystal structure is characterized by comprising the steps of processing a plurality of blind holes in the surface of a magnesium alloy plate, adding powder A into the blind holes, performing primary friction stir processing on the magnesium alloy plate filled with the powder A at the temperature of-196-26 ℃ by using a friction stir processing device, and performing heat treatment on the processed plate to obtain the magnesium alloy material, wherein the powder A is one or more mixed powder of vanadium nitride, silicon carbide or titanium diboride;
the blind holes are cylindrical, the diameter D of each blind hole is 1-3 mm, the distance a between every two rows of blind holes is 4-6 mm, and the distance b between every two rows of blind holes is 7-9 mm;
the stirring head used in the friction stir processing process comprises a shaft shoulder and a stirring needle, wherein the shaft shoulder and the stirring needle are both cylindrical;
the thickness of the magnesium alloy plate is 1-10 mm, the diameter of a shaft shoulder of the stirring head is 8-30 mm, the diameter of the stirring pin is larger than the diameter of the blind hole by 0.5-2 mm, namely the diameter of the stirring pin is 1.5-5 mm, the length of the stirring pin is smaller than the thickness of the magnesium alloy plate by 0.2-0.5 mm, namely the length of the stirring pin is 0.8-9.5 mm, the depth of the blind hole is smaller than the length of the stirring pin by 0-1 mm, namely the depth of the blind hole is 0.8-8.5 mm;
the heat treatment temperature is 0.35Tm～0.45TmWherein, TmThe melting point of the material is shown, and the heat preservation time is 10-30 min;
the friction stir processing parameters are as follows: the rotating speed of the stirring head is 600-1500 rpm, the advancing speed is 20-40 mm/min, and the pressing amount of the shaft shoulder is 0.1-0.3 mm.
2. The method for producing a magnesium alloy material having a mixed crystal structure according to claim 1, characterized by specifically comprising:
processing a plurality of blind holes which are arranged in parallel and in multiple rows on the surface of the magnesium alloy plate, adding vanadium nitride into the blind holes, performing friction stir processing on the magnesium alloy plate filled with the vanadium nitride by adopting a friction stir processing device at the temperature of 5-26 ℃, and performing heat treatment on the processed plate to obtain the magnesium alloy plate,
the diameter D of the blind holes is 2mm, the distance a between every two rows of blind holes is 5mm, the distance b between every two rows of blind holes is 8mm, the depth of the blind holes is 3.7mm, the diameter of a stirring pin is 4mm, the length of the stirring pin is 3.7mm, the diameter of a shaft shoulder of a stirring head is 16mm, the pressing amount of the shaft shoulder is 0.2mm, the rotating speed of the stirring head is 750rpm, the advancing speed is 30mm/min, the heat treatment temperature is 228 ℃, and the heat preservation time is 20 min.
3. The magnesium alloy material with the mixed crystal structure is characterized by being prepared by the preparation method of any one of the magnesium alloy materials with the mixed crystal structure in claims 1-2, wherein the product of strength and elongation of the prepared magnesium alloy material with the mixed crystal structure is 4446.75-4764.42 MPa.
CN201910822560.8A 2019-09-02 2019-09-02 Magnesium alloy material with mixed crystal structure and preparation method thereof Active CN110666447B (en)

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