Layered nano-heterogeneous high strength and toughness magnesium alloy plate based on centrifugal casting and preparation method thereof

Abstract

The application provides a preparation method of a layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate based on centrifugal casting, and the method comprises the following steps: smelting a first magnesium alloy material to obtain a first magnesium alloy solution, and smelting a second magnesium alloy material to obtain a second magnesium alloy solution; alternately performing centrifugal casting by using the first magnesium alloy solution and the second magnesium alloy solution; sequentially performing solid solution, water quenching, hot rolling and cold rolling treatment to obtain a multi-layer magnesium alloy plate; sequentially performing recrystallization annealing treatment and aging treatment to obtain a layered nano-heterogeneous magnesium alloy plate; and the layered nano-heterogeneous magnesium alloy plate comprises a nano-platelet-shaped Mg 17 Al 12 phase precipitated along a basal plane of a close-packed hexagonal crystal structure, and a disc-shaped nano-beta' phase precipitated along a column surface of the close-packed hexagonal crystal structure. The method has great flexibility and directionality in microstructure design, and can prepare a series of layered heterogeneous magnesium alloys, which have the characteristics of high toughness, high strength and excellent high-temperature creep resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material processing, in particular to a layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate based on centrifugal casting and a preparation method thereof. BACKGROUND

[0002] Magnesium alloy is the lightest metal structural material in the field of engineering application, which has the advantages of low density, high specific strength and specific stiffness, good vibration and noise reduction performance, excellent casting performance, dimensional stability and easy recycling, and has broad application prospects in the fields of automobile industry, instruments and meters, aerospace, etc.

[0003] Compared with aluminum alloy, titanium alloy, high-temperature alloy and other materials, magnesium alloy has the disadvantages of low strength, poor plasticity, poor corrosion resistance and low creep performance, and at present, alloying elements are added to strengthen the magnesium alloy material. For example, rare earth elements such as gadolinium, yttrium and neodymium are added to magnesium alloy to form rare earth magnesium alloy. After aging heat treatment, high-density nano precipitates are formed in the material, which can strongly hinder dislocation slip movement and greatly improve the strength and creep performance of magnesium alloy. In addition, during high-temperature deformation of the rare earth magnesium alloy, nano precipitates can effectively hinder grain boundary slip and dislocation climb, greatly reducing the steady-state creep rate, so the rare earth magnesium alloy has more excellent high-temperature creep resistance than AZ and AM series magnesium alloys.

[0004] However, the toughness of the rare earth magnesium alloy will be greatly reduced, and the plastic deformation ability is not strong, which greatly limits the application range of the rare earth magnesium alloy in actual production. Therefore, how to prepare magnesium alloy materials with high strength and high toughness has become a research hotspot in the field of metal structural materials.

[0005] Heterogeneous metal materials, also known as non-homogeneous metal materials, have the characteristics of large strength difference between different interface regions inside the material. This non-uniformity in strength is caused by factors such as different microstructures, different crystal structures or uneven element distribution. It has been found through research that during deformation, a large strain gradient is formed at the interface of heterogeneous metal materials, and the heterogeneous deformation-induced stress not only strengthens the metal material, but also further improves the work hardening capacity of the metal material, thereby obtaining excellent toughness.

[0006] At present, large plastic deformation technology is an effective way to prepare bulk high-strength and high-toughness heterogeneous metal materials. For example, Chinese invention patent CN108796330A discloses a preparation method of ultra-high-strength Mg-Gd-Y-Zr nano-heterogeneous magnesium alloy. The method uses rotary forging deformation technology to process an extruded Mg-Gd-Y-Zr alloy rod to prepare a nano-heterogeneous magnesium alloy material with a grain size of 30nm-2μm, and then combines a heat treatment process to make the yield strength of the magnesium alloy reach 470MPa and the elongation after fracture reach 6%.

[0007] However, it has the following limitations:

[0008] 1. The thermal stability and plastic deformation ability of nanocrystals are poor, so the work hardening ability and high temperature resistance of the prepared nanoheterogeneous magnesium alloy material are not strong, and the uniformity and elongation are not high;

[0009] 2. The preparation process of magnesium alloy rods is complicated, the extruded rods for rotary forging need to be polished, heated and deformed multiple times, the technical requirements under high temperature rotary forging are very high, and the production efficiency is low;

[0010] 3. The method is only suitable for preparing rods, and it is difficult to realize the processing and preparation of plate-shaped materials.

[0011] Therefore, it is necessary to improve the magnesium alloy material and its preparation method to solve the above problems. SUMMARY

[0012] In order to solve the problems of poor thermal stability, poor plastic deformation ability, complicated processing process and low efficiency of magnesium alloy material, a layered nanoheterogeneous high strength and toughness magnesium alloy plate based on centrifugal casting and a preparation method are disclosed. The design idea of the layered nanoheterogeneous high strength and toughness magnesium alloy plate is to select two or more magnesium alloys with different recrystallization temperatures and aging precipitation characteristics as raw materials, to prepare a plate-shaped heterogeneous structure magnesium alloy material by centrifugal casting and rolling deformation method, and to control the precipitation of different nanometer precipitates by combining aging heat treatment process. Finally, a layered nanoheterogeneous high strength and toughness magnesium alloy plate with multi-scale precipitation is prepared.

[0013] The technical scheme for achieving the purpose of the application is as follows:

[0014] In the first example of the present application, a preparation method of a layered nanoheterogeneous high strength and toughness magnesium alloy plate based on centrifugal casting is provided, and the preparation method comprises:

[0015] Step 1, melting the first magnesium alloy material to obtain a first magnesium alloy solution, and melting the second magnesium alloy material to obtain a second magnesium alloy solution, wherein the types of metal elements other than magnesium element in the first magnesium alloy material and the second magnesium alloy material are different;

[0016] Step 2, based on the centrifugal casting method, the first magnesium alloy solution and the second magnesium alloy solution are alternately centrifuged to prepare a multi-layer magnesium alloy casting;

[0017] Step 3, solid solution treatment, water quenching treatment, hot rolling treatment and cold rolling treatment are carried out on the multi-layer magnesium alloy casting to obtain a multi-layer magnesium alloy plate;

[0018] Step 4, sequentially performing recrystallization annealing treatment and aging treatment on the multi-layer magnesium alloy plate to obtain a layered nano-heterostructure magnesium alloy plate;

[0019] The layered nano-heterostructure magnesium alloy plate comprises Mg 17 Al 12 phase precipitated along the basal plane of the hexagonal close-packed structure, and a nano β' phase precipitated along the column surface of the hexagonal close-packed structure.

[0020] Further, in the step 1, the recrystallization temperature of the first magnesium alloy material is higher than that of the second magnesium alloy material.

[0021] Further, in the step 1, the first magnesium alloy material comprises any one of Mg-Gd alloy, Mg-Gd-Y-Zr alloy, Mg-Gd-Y-Zr-Ca alloy, and the second magnesium alloy material comprises any one of Mg-Mn alloy, Mg-Al alloy, and Mg-Zn alloy.

[0022] Further, in the step 4, in the layered nano-heterostructure magnesium alloy plate, the Mg 17 Al 12 phase is located in the casting layer formed by the second magnesium alloy solution, and the nano β' phase is located in the casting layer formed by the first magnesium alloy solution.

[0023] Further, in the step 1, the first magnesium alloy material and the second magnesium alloy material are both smelted in a crucible resistance furnace with SF6 and CO2 mixed gas at 650-800℃ for 5-10h.

[0024] Further, in the step 3, the multi-layer magnesium alloy casting is a multi-layer magnesium alloy ring-shaped casting, and the hot rolling treatment method of the multi-layer magnesium alloy ring-shaped casting comprises:

[0025] According to the user's needs, cutting along the radial direction of the multi-layer magnesium alloy ring-shaped casting to obtain a multi-layer magnesium alloy arc-shaped plate;

[0026] First hot rolling the multi-layer magnesium alloy arc-shaped plate with a first temperature to obtain a multi-layer magnesium alloy flat plate;

[0027] Hot rolling the multi-layer magnesium alloy flat plate with a second temperature at least once to obtain a multi-layer magnesium alloy plate before cold rolling.

[0028] Further, the first temperature is higher than the second temperature.

[0029] Further, in the step 4, the multi-layer magnesium alloy plate is subjected to recrystallization annealing treatment at 300-450 DEG C for 30-60 min in a vacuum furnace with argon gas protection.

[0030] Further, in the step 4, the multi-layer magnesium alloy plate is subjected to aging treatment at 180-250 DEG C for 15-30 h in a constant temperature oil bath furnace.

[0031] In the second example of the present application, a layered nano-heterostructured high-strength and high-toughness magnesium alloy plate based on centrifugal casting is provided, which is formed by sequentially and alternately casting a first magnesium alloy solution and a second magnesium alloy solution;

[0032] The first magnesium alloy solution and the second magnesium alloy solution are different in the types of metal elements other than magnesium element, the recrystallization annealing temperature of the first magnesium alloy layer formed by the first magnesium alloy solution is different from that of the second magnesium alloy layer formed by the second magnesium alloy solution, and the nano-precipitated phases in the first magnesium alloy layer and the second magnesium alloy layer are different.

[0033] Further, the first magnesium alloy layer includes Mg 17 Al 12 nanoplatelets precipitated along the basal plane of the close-packed hexagonal crystal structure, and the second magnesium alloy layer includes disc-shaped nano-beta' phase precipitated along the prism plane of the close-packed hexagonal crystal structure.

[0034] Alternatively, the first magnesium alloy layer includes disc-shaped nano-beta' phase precipitated along the prism plane of the close-packed hexagonal crystal structure, and the second magnesium alloy layer includes Mg 17 Al 12 nanoplatelets precipitated along the basal plane of the close-packed hexagonal crystal structure.

[0035] Further, the layered nano-heterostructured high-strength and high-toughness magnesium alloy plate includes at least 3 layers of magnesium alloy plates.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] 1. The layered nano-heterostructured high-strength and high-toughness magnesium alloy plate is prepared by using the centrifugal casting method, combining with the deformation hot rolling treatment process, the recrystallization annealing treatment process and the aging treatment process, has great flexibility and directionality in microstructure design, can adjust the selection of magnesium alloy material according to the requirements, and can prepare a series of layered heterostructured magnesium alloys.

[0038] 2. The layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate prepared by the centrifugal casting method can realize perfect metallurgical bonding at the interface of the two magnesium alloy materials, and can avoid the problem of interlayer peeling caused by the stacking and rolling of two or more layers of metal plates, thereby ensuring the integrity of the casting.

[0039] 3. The layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate prepared by using magnesium alloy materials with different recrystallization annealing temperatures can realize the double heterogeneity of grain structure and internal nano-precipitated phase (i.e. the nano-platelet-shaped Mg 17 Al 12 phase precipitated along the basal plane of the hexagonal close-packed crystal structure, and the disc-shaped nano-β' phase precipitated along the column surface of the hexagonal close-packed crystal structure), so that the heterogeneous deformation-induced stress at the interface of adjacent layers is beneficial to the additional activation of non-basal slip systems, and the finally prepared layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate has the advantages of high strength of hard phase, high toughness of soft phase, and excellent high-temperature creep resistance.

[0040] 4. Using the centrifugal casting method, a large-size, layer number and layer thickness controllable layered nano-heterogeneous magnesium alloy plate can be prepared, which can meet the various requirements of the industry for magnesium alloy performance indicators. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows.

[0042] Figure 1 The flowchart of the preparation method of the layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate based on centrifugal casting in Example 1;

[0043] Figure 2 The schematic diagram of the layered magnesium alloy ring-shaped casting in Example 1;

[0044] Figure 3 The schematic diagram of the first hot rolling of the multi-layer magnesium alloy arc-shaped plate in Example 1;

[0045] Figure 4 The schematic diagram of the multiple hot rolling and cold rolling of the multi-layer magnesium alloy flat plate in Example 1;

[0046] Figure 5a The schematic diagram of the grains in the AZ31B material in Example 1;

[0047] Figure 5b The schematic diagram of the grains in the GW103K material in Example 1;

[0048] Figure 6 The schematic diagram of the structure of the soft and hard phases inside the layered nano-heterogeneous magnesium alloy plate after recrystallization annealing in Example 1;

[0049] Figure 7a Schematic diagram of the nanodisc-shaped β' phase in the GW103K material in the aged layered nanoheterostructured magnesium alloy plate in Example 1 17 Al 12 Schematic diagram of the nanodisc-shaped β' phase in the GW103K material in the aged layered nanoheterostructured magnesium alloy plate in Example 1

[0050] Figure 7b Schematic diagram of the nanodisc-shaped β' phase in the GW103K material in the aged layered nanoheterostructured magnesium alloy plate in Example 1

[0051] Wherein, 6, layered magnesium alloy annular casting; 7, multi-layered magnesium alloy arc plate; 8, upper and lower compression rollers; 9, multi-layered magnesium alloy flat plate; 10, multi-layered magnesium alloy flat plate with a set thickness; 11, multi-layered magnesium alloy flat plate after cold rolling. DETAILED DESCRIPTION

[0052] The advantages and features of the present application will become more apparent with the description of specific embodiments. However, these embodiments are only exemplary and do not constitute any limitation on the scope of the present application. Those skilled in the art should understand that the details and forms of the technical solutions of the present application can be modified or replaced without departing from the spirit and scope of the present application, and such modifications and replacements fall within the protection scope of the present application.

[0053] Example 1

[0054] The present embodiment discloses a preparation method of a layered nanoheterostructured high-strength and high-toughness magnesium alloy plate based on centrifugal casting, as shown in Figure 1 The preparation method comprises the following steps:

[0055] Step 1, melting a first magnesium alloy material to obtain a first magnesium alloy solution, and melting a second magnesium alloy material to obtain a second magnesium alloy solution, wherein the types of metal elements other than magnesium in the first magnesium alloy material and the second magnesium alloy material are different.

[0056] In this step, the recrystallization temperature of the first magnesium alloy material is higher than that of the second magnesium alloy material.

[0057] Specifically, the first magnesium alloy material includes any one of Mg-Gd alloy, Mg-Gd-Y-Zr alloy, and Mg-Gd-Y-Zr-Ca alloy, and the second magnesium alloy material includes any one of Mg-Mn alloy, Mg-Al alloy, and Mg-Zn alloy.

[0058] Step 2, based on the centrifugal casting method, the first magnesium alloy solution and the second magnesium alloy solution are alternately centrifugally cast to prepare a multi-layered magnesium alloy casting.

[0059] Step 3, solid solution treatment, water quenching treatment, hot rolling treatment, cold rolling treatment are performed on the multi-layer magnesium alloy casting to obtain a multi-layer magnesium alloy plate;

[0060] Step 4, recrystallization annealing treatment and aging treatment are performed on the multi-layer magnesium alloy plate in sequence to obtain a layered nano-heterostructure magnesium alloy plate;

[0061] The layered nano-heterostructure magnesium alloy plate comprises Mg 17 Al 12 phase precipitated along the basal plane of the hexagonal close-packed structure, and disc-shaped nano-β' phase precipitated along the column surface of the hexagonal close-packed structure.

[0062] In this step, the Mg 17 Al 12 phase in the layered nano-heterostructure magnesium alloy plate is located in the casting layer formed by the second magnesium alloy solution, and the nano-β' phase is located in the casting layer formed by the first magnesium alloy solution.

[0063] Further, in the above step 1, the smelting conditions of the first magnesium alloy material and the second magnesium alloy material are as follows: in a crucible resistance furnace with SF6 and CO2 mixed gas, smelting at 650-800℃ for 5-10h. Specifically, during smelting, the magnesium alloy material with higher recrystallization annealing temperature among the first magnesium alloy material and the second magnesium alloy material has a slightly higher smelting temperature to ensure that the magnesium alloy material is fully melted into a magnesium alloy liquid.

[0064] Further, in the above step 2, the first magnesium alloy solution can be used as the first layer during casting, or the second magnesium alloy solution can be used as the first layer, and only the alternation of casting is required during the preparation of the multi-layer magnesium alloy casting, and the casting order is not limited.

[0065] This embodiment takes ring casting as an example to illustrate the casting process:

[0066] First, the first magnesium alloy solution (or the second magnesium alloy solution) is cast into the bushing mold through the sprue, and after the casting is completed, the centrifuge continues to operate for 30-60min, and the ring-shaped casting with one layer (i.e. the first magnesium alloy layer) is obtained after demolding;

[0067] The inner surface of the ring-shaped casting is turned to remove impurities and oxidation layer on the surface, and the inner surface of the ring-shaped casting is pickled with 30% chromic acid solution for 1-2min, and then rinsed with deionized water and alcohol and dried;

[0068] Secondly, the ring-shaped casting is put into the bushing mold again, and a second casting is performed using a second magnesium alloy solution (or the first magnesium alloy solution). After the casting is completed, the centrifuge is continuously operated for 30-60 min, and a ring-shaped casting with two layers of different magnesium alloys (i.e., a first layer of magnesium alloy and a second layer of magnesium alloy) is obtained by demolding.

[0069] The inner surface of the ring-shaped casting is turned to remove impurities and an oxide layer on the surface. The inner surface of the ring-shaped casting is pickled using a 30% chromic acid solution for 1-2 min, rinsed with deionized water and alcohol, and then dried.

[0070] The above casting, surface treatment, and cleaning processes are repeated multiple times until a multi-layer magnesium alloy casting is formed.

[0071] It should be noted that the number of layers of the multi-layer magnesium alloy casting is determined according to user requirements, and can be 2 layers, 3 layers, or more than 3 layers.

[0072] Further, in step 3 above, the multi-layer magnesium alloy casting is subjected to solid solution treatment and water quenching treatment using existing general methods, for example: the multi-layer magnesium alloy casting is placed in a vacuum tube furnace with argon protection, and is subjected to solid solution treatment at 450-540°C for 12-24 h; after the solid solution treatment is completed, the multi-layer magnesium alloy casting is rapidly water quenched to ensure that the solute atoms are completely dissolved in the matrix to form a supersaturated solid solution.

[0073] Further, in step 3 above, the multi-layer magnesium alloy casting formed by casting can have a ring-shaped structure or a plate-shaped structure. When the multi-layer magnesium alloy casting has a plate-shaped structure, it can be cut according to user requirements, and subjected to multiple hot rolling at the same temperature until the required thickness is reached. When the multi-layer magnesium alloy casting has a ring-shaped structure, after being cut along the radial direction according to user requirements, the obtained multi-layer magnesium alloy flat plate has a certain arc, and the hot rolling method needs to be redesigned to ensure that the magnesium alloy plate has good interface bonding effect after hot rolling.

[0074] In the specific embodiment, to reduce the casting difficulty, the bushing mold is designed to have a ring-shaped structure, so that the multi-layer magnesium alloy casting after casting is a multi-layer magnesium alloy ring-shaped casting. The hot rolling method of the multi-layer magnesium alloy ring-shaped casting includes:

[0075] According to user requirements, the multi-layer magnesium alloy ring-shaped casting is cut along the radial direction to obtain a multi-layer magnesium alloy arc-shaped plate.

[0076] On a small double-roller machine, the upper and lower rollers are synchronously rotated at a linear speed of 50-100 mm / s. The multi-layer magnesium alloy arc-shaped plate is first hot rolled at a first temperature to obtain a multi-layer magnesium alloy flat plate.

[0077] The multi-layered magnesium alloy plate is subjected to at least one hot rolling at a second temperature until a preset thickness is reached to form a pre-cold-rolled multi-layered magnesium alloy plate.

[0078] Further, the first temperature is greater than the second temperature, and in the embodiment, the difference between the first temperature and the second temperature is about 50-150°C, for example, when the first temperature is 400-500°C, the second temperature is 300-400°C.

[0079] The hot rolling makes the multi-layered magnesium alloy plate have high-density interfaces, and the multi-layered magnesium alloy plate is subjected to cold rolling after the hot rolling to make the deformation amount reach 15-20%, so that the multi-layered magnesium alloy plate has enough crystal defects, including dislocations, deformation twins and stacking faults.

[0080] Further, in the step 4, the recrystallization annealing of the multi-layered magnesium alloy plate is performed in a vacuum furnace with argon protection at a temperature of 300-450°C for 30-60 min.

[0081] During the recrystallization annealing, the recrystallization temperature of different layers of the multi-layered magnesium alloy plate is obviously different, one kind of magnesium alloy material quickly forms grain nucleation and growth, and the obtained grain structure is relatively coarse, and the recrystallization process of another kind of magnesium alloy material is relatively slow, and the obtained grain structure is uniform and fine.

[0082] Further, in the step 4, the aging treatment of the multi-layered magnesium alloy plate after the recrystallization annealing is performed in a constant-temperature oil bath furnace at a temperature of 180-250°C for 15-30 h.

[0083] During the aging treatment, the multi-layered magnesium alloy plate after the recrystallization annealing has different grain structures and obvious differences in aging precipitation characteristics between different layers, mainly including that rod-shaped precipitated phases are precipitated along the basal plane of the hexagonal close-packed structure in the matrix of one kind of magnesium alloy material, and fine and uniform disc-shaped nanometer precipitated phases are precipitated along the cylindrical surface of the hexagonal close-packed structure in the matrix of another kind of magnesium alloy material, and these metastable or equilibrium precipitated phases strongly hinder dislocation slip, thereby effectively strengthening the matrix.

[0084] The present embodiment takes GW103K rare earth magnesium alloy (main components: Mg-10wt% Gd-3wt% Y-0.5wt% Zr-0.4wt% Ca) of Mg-Gd-Y-Zr-Ca alloy as the first magnesium alloy material, and AZ31B (main components: Mg-3wt% Al-1wt% Zn-0.5wt% Mn) of Mg-Al alloy as the second magnesium alloy material as examples to illustrate the preparation method of the layered nano-heterostructure high strength and toughness magnesium alloy plate. The preparation steps include:

[0085] Step one: centrifugal casting, the GW103K magnesium ingot is placed in a 750°C crucible resistance furnace for melting, the melting is carried out under SF6 and CO2 mixed gas protection for 10h; the centrifugal power equipment is started, the rotating speed is 1000r / min, the GW103K metal liquid is first cast into the bushing mold through the sprue, after the casting is completed, the centrifuge continues to run for 50min, and then the mold is removed to obtain a ring-shaped casting; the inner surface of the ring-shaped casting is turned and the impurities and oxide layer on the surface are removed, and the inner surface is pickled with 30% chromic acid solution for 2min, then washed with deionized water and alcohol and dried.

[0086] The obtained ring-shaped casting is placed in the bushing mold, the AZ31B magnesium ingot is placed in a 700°C crucible resistance furnace for melting, the melting is carried out under SF6 and CO2 mixed gas protection for 8h; the centrifugal equipment is started, the rotating speed is 1000r / min, the AZ31B metal liquid is cast into the bushing, after the casting is completed, the centrifuge continues to run for 40min, and then the mold is removed to obtain a ring-shaped casting with two layers of different magnesium alloys; the above melting, casting and pickling process is repeated for multiple times to obtain a layered magnesium alloy ring-shaped casting 6, as shown in Figure 2 .

[0087] It should be noted that the GW103K magnesium ingot and the AZ31B magnesium ingot can both be used as the first layer of the layered magnesium alloy ring-shaped casting 6.

[0088] Step two: solid solution treatment, the obtained layered magnesium alloy ring-shaped casting 6 is placed in a vacuum tube furnace under argon protection for solid solution treatment, the solid solution temperature is 530°C, the solid solution time is 12h, and after the solid solution is completed, the casting is quickly water quenched to form a supersaturated solid solution in the matrix;

[0089] Step three: rolling deformation, the obtained layered magnesium alloy ring-shaped casting 6 is cut to obtain a suitable size; as shown in Figure 3 , the cut layered magnesium alloy arc-shaped plate 7 is placed on a small rolling mill for 450°C hot rolling deformation, the synchronous linear speed of the upper and lower compression rollers 8 is set to 80mm / s to obtain a layered magnesium alloy flat plate 9.

[0090] As shown in Figure 4As shown, the multi-layer magnesium alloy plate 9 is subjected to multi-pass hot rolling deformation at 400°C to a thickness of 10 mm, and the plate is densified by high-temperature and high-strain methods; finally, the multi-layer magnesium alloy plate 10 of the set thickness after hot rolling is subjected to cold rolling to obtain the multi-layer magnesium alloy plate 11 after cold rolling, with a deformation of 20%, and a large number of crystal defects such as dislocations, deformation twins and stacking faults are accumulated in the material, which provides sufficient driving force for subsequent nucleation and growth of recrystallization.

[0091] Step four: recrystallization annealing treatment, the multi-layer magnesium alloy plate 11 after cold rolling is placed in a vacuum tube furnace protected by argon gas for heat treatment. The annealing temperature is set to 450°C, and the holding time is 30 min. Since the recrystallization temperatures of AZ31B and GW103K materials are different, the soft-phase AZ31B material will quickly undergo grain nucleation and growth, and the obtained grain structure is relatively coarse, as shown in Figure 5a , and the average grain size is 45 μm; while the recrystallization process of the hard-phase GW103K material is relatively slow, and the obtained grain structure is small and uniformly distributed, as shown in Figure 5b , and the average grain size is 1.5 μm, and a multi-grain scale distribution layered nanohetero magnesium alloy plate is obtained, and the structure diagram of the soft and hard phases in the material is as shown in Figure 6 .

[0092] Step five: aging treatment, the layered nanohetero magnesium alloy plate after annealing is placed in a constant-temperature oil bath furnace for aging treatment. The aging temperature is set to 180°C, and the holding time is 20 h. Since the aging precipitation characteristics of AZ31B and GW103K materials are significantly different, after aging, a large number of nanometer plate-shaped Mg 17 Al 12 phases are precipitated in the AZ31B material along the basal plane of the close-packed hexagonal crystal structure, as shown in Figure 7a ; while the GW103K material uniformly precipitates disc-shaped nanometer β' phases along the column surface of the close-packed hexagonal crystal structure, as shown in Figure 7b .

[0093] The uniaxial tensile test of the prepared layered nanohetero magnesium alloy material shows that: the layered nanohetero magnesium alloy material prepared from AZ31B and GW103K by centrifugal casting realizes the dual heterostructure of grain structure and internal nanometer precipitated phase in the microstructure, the stress-induced strengthening and toughening effect of the material is obvious, and the yield strength of the finally prepared sample is as high as 480-495 MPa, the tensile strength is as high as 560-580 MPa, the uniform elongation is 15%-18%, and the fracture elongation is 16%-19%. The strengthening and toughening micro-mechanism of this type of magnesium alloy material mainly reflects in the following four aspects:

[0094] ①The large strain gradient will be formed at the interface of different materials, and the heterogeneous deformation induced stress is beneficial to the improvement of the work hardening ability of magnesium alloy, thereby strengthening the magnesium alloy material;

[0095] ②The lattice distortion field is formed at the interface by the different bonding state (coherent or partially coherent matching relationship) of the basal plane or columnar precipitated phase and the matrix, thereby strengthening the matrix;

[0096] ③The strong interaction between the precipitated phase and the dislocation stress field during the deformation process hinders the slip movement of the dislocation, thereby strengthening the magnesium alloy;

[0097] ④The basal plane dislocation shearing the precipitated phase during the deformation process will cause local lattice mismatch, and a large number of non-basal plane dislocations will be activated under high stress, which is helpful to coordinate the tensile strain, thereby improving the tensile plasticity of the heterogeneous magnesium alloy sample.

[0098] The embodiment can also be applied to other magnesium alloy materials with different fine-grain strengthening and precipitate strengthening effects. For example, AZ91 and GW103K magnesium alloys, AM60 and GW83K magnesium alloys, ZK60 and WE43 magnesium alloys, etc. By using the method proposed in the present application, a multi-scale precipitated large block layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate can be obtained.

[0099] Embodiment 2:

[0100] The embodiment discloses a layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate based on centrifugal casting, which is a magnesium alloy plate formed by alternately pouring a first magnesium alloy solution and a second magnesium alloy solution to form at least 3 layers.

[0101] The first magnesium alloy solution and the second magnesium alloy solution are different in the types of metal elements except magnesium, the recrystallization annealing temperature of the first magnesium alloy layer formed by the first magnesium alloy solution is different from that of the second magnesium alloy layer formed by the second magnesium alloy solution, and the nano-precipitated phases in the first magnesium alloy layer and the second magnesium alloy layer are different.

[0102] Further, the first magnesium alloy layer includes Mg 17 Al 12 phase precipitated along the basal plane of the close-packed hexagonal crystal structure, and the average grain size of the crystals in the magnesium alloy layer is 40-80 μm. The second magnesium alloy layer includes disc-shaped nano-β' phase precipitated along the columnar surface of the close-packed hexagonal crystal structure, and the average grain size of the crystals in the magnesium alloy layer is 1-5 μm;

[0103] Alternatively, the first magnesium alloy layer includes disc-shaped nano-β' phase precipitated along the columnar surface of the close-packed hexagonal crystal structure, and the second magnesium alloy layer includes Mg17 Al 12 phases.

[0104] The preparation method of the layered nano-heterostructured high-strength and high-toughness magnesium alloy plate based on centrifugal casting provided by the specific embodiment has the following advantages compared with the prior art:

[0105] 1. The layered nano-heterostructured high-strength and high-toughness magnesium alloy plate is prepared by adopting a centrifugal casting method, combining a deformation hot rolling process, a recrystallization annealing process and an aging treatment process, has great flexibility and directivity of microstructure design, can adjust the selection of magnesium alloy materials according to requirements, and can prepare a series of layered heterostructured magnesium alloys.

[0106] 2. The interface of the two magnesium alloy materials of the layered nano-heterostructured high-strength and high-toughness magnesium alloy plate prepared by the centrifugal casting method can realize perfect metallurgical bonding, can avoid the problem of interlayer peeling caused by the stacking and rolling of two or more metal plates, and further ensures the integrity of the casting.

[0107] 3. The layered nano-heterostructured high-strength and high-toughness magnesium alloy plate made of magnesium alloy materials with different recrystallization annealing temperatures can realize double heterostructure of grain organization and internal nano precipitated phases (i.e. nano platelet-shaped Mg 17 Al 12 phases along the basal plane of the hexagonal close-packed structure and disc-shaped nano β' phases along the column surface of the hexagonal close-packed structure), so that the heterogeneous deformation induced stress at the interface of adjacent layers is beneficial to the additional activation of non-basal slip systems, and the finally prepared layered nano-heterostructured high-strength and high-toughness magnesium alloy plate has the advantages of high strength of hard phases, high toughness of soft phases, and excellent high-temperature creep resistance.

[0108] 4. Using the centrifugal casting method, a large-size layered nano-heterostructured magnesium alloy plate with controllable number of layers and layer thickness can be prepared, which can meet various requirements of the industry on the performance indicators of magnesium alloys.

[0109] 5. The layered nano-heterostructured high-strength and high-toughness magnesium alloy plate prepared by the method has a wide range of applications and can be used to prepare magnesium alloy workpieces with high toughness, high strength and high-temperature creep resistance.

[0110] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0111] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. A method for preparing layered nano-heterogeneous high-strength and high-toughness magnesium alloy plates based on centrifugal casting, characterized in that, Preparation methods include: Step 1: Melt a first type of magnesium alloy material to obtain a first type of magnesium alloy solution; melt a second type of magnesium alloy material to obtain a second type of magnesium alloy solution. The first type of magnesium alloy material and the second type of magnesium alloy material contain different metal elements except for magnesium. The second type of magnesium alloy material is a Mg-Al alloy. The recrystallization temperature of the first type of magnesium alloy material is higher than that of the second type of magnesium alloy material. The first type of magnesium alloy material includes any one of the following: Mg-Gd alloy, Mg-Gd-Y-Zr alloy, or Mg-Gd-Y-Zr-Ca alloy. Step 2: Based on the centrifugal casting method, the first magnesium alloy solution and the second magnesium alloy solution are alternately centrifugally cast to prepare multi-layer magnesium alloy castings; Step 3: Perform solution treatment, water quenching, hot rolling and cold rolling on the multilayer magnesium alloy casting to obtain multilayer magnesium alloy plates; Step 4: Perform recrystallization annealing and aging treatment on the multilayer magnesium alloy sheet in sequence to obtain layered nano-heterogeneous magnesium alloy sheet; The layered nano-heterogeneous magnesium alloy plate comprises Mg nanoplate strips precipitated along the basal plane of a close-packed hexagonal crystal structure. 17 Al 12 The Mg phase, along the prismatic planes of the close-packed hexagonal crystal structure, precipitates in a disk-shaped nano-β' phase. 17 Al 12 The phase is located in the casting layer formed by the second type of magnesium alloy solution, and the nano β' phase is located in the casting layer formed by the first type of magnesium alloy solution.

2. The preparation method according to claim 1, characterized in that, In step 1, both the first type of magnesium alloy material and the second type of magnesium alloy material are smelted in a crucible resistance furnace with a mixture of SF6 and CO2 gas, at 650~800 °C for 5~10 h.

3. The preparation method according to claim 1, characterized in that, In step 3, the multi-layer magnesium alloy casting is a multi-layer magnesium alloy ring casting, and the hot rolling treatment method for the multi-layer magnesium alloy ring casting includes: According to user requirements, the multi-layer magnesium alloy ring casting is cut along the radial direction to obtain a multi-layer magnesium alloy arc plate. The multi-layer magnesium alloy arc plate is hot-rolled for the first time at a first temperature to obtain a multi-layer magnesium alloy flat plate. The multilayer magnesium alloy plate is hot-rolled at least once at a second temperature to obtain a multilayer magnesium alloy plate before cold rolling.

4. The preparation method according to claim 3, characterized in that, The first temperature is greater than the second temperature.

5. The preparation method according to claim 1, characterized in that, In step 4, the multilayer magnesium alloy plate is subjected to recrystallization annealing treatment in a vacuum furnace with argon protective gas, at 300~450 ℃ for 30~60 min.

6. The preparation method according to claim 1 or 5, characterized in that, In step 4, the multilayer magnesium alloy sheet is aged in a constant temperature oil bath furnace at 180~250 ℃ for 15~30 h.

7. A layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate based on centrifugal casting, characterized in that: The layered nano-heterogeneous high-strength and high-toughness magnesium alloy plate is formed by sequentially casting a first magnesium alloy solution and a second magnesium alloy solution using the preparation method described in any one of claims 1 to 6. The first magnesium alloy solution and the second magnesium alloy solution contain different types of metallic elements except for magnesium. The recrystallization annealing temperatures of the first magnesium alloy layer formed from the first magnesium alloy solution and the second magnesium alloy layer formed from the second magnesium alloy solution are different. Furthermore, the nano-precipitated phases in the first and second magnesium alloy layers are different. The first magnesium alloy layer includes Mg nanoplatelets precipitated along the basal plane of a close-packed hexagonal crystal structure. 17 Al 12 The second magnesium alloy layer includes disk-shaped nano-β' phases precipitated along the prismatic faces of a close-packed hexagonal crystal structure; or, the first magnesium alloy layer includes disk-shaped nano-β' phases precipitated along the prismatic faces of a close-packed hexagonal crystal structure, and the second magnesium alloy layer includes nano-lamellar Mg phases precipitated along the basal faces of a close-packed hexagonal crystal structure. 17 Al 12 Mutually.

Images