阅读说明：本技术 一种层状双尺度镁合金的制备方法 (Preparation method of layered double-scale magnesium alloy ) 是由 徐岩 李玮 虎鹏鸿 阎泽文 刘孝轲 贾建波 杨志刚 彭伟劲 于 2019-10-25 设计创作，主要内容包括：本发明提供一种层状双尺度镁合金的制备方法,属于轻金属材料加工领域。其包括：将经过加热均匀化处理的镁合金板坯于280-370℃下等温加热20-30min后,立即进行第一道次轧制变形,轧制的应变速率为3.5-4.9s<Sup>-1</Sup>,得到变形板材；在对变形板材进行退火处理后,于280-340℃下进行第二道次轧制变形,轧制的应变速率为6.0-7.1s<Sup>-1</Sup>。这种层状双尺度镁合金的制备方法,采用高应变速率、梯度降温双道次轧制,能够获得具有层状双尺度组织结构的高强韧镁合金材料,超细晶层和微米晶层的交替层状分布,提高了镁合金的强度和塑韧性。(The invention provides a preparation method of a layered double-scale magnesium alloy, belonging to the field of light metal material processing. It includes: heating the magnesium alloy plate blank subjected to heating homogenization treatment at the temperature of 280-370 ℃ for 20-30min at the equal temperature, and immediately performing first-pass rolling deformation at the rolling strain rate of 3.5-4.9s ‑1 Obtaining a deformed plate; after the deformed plate is annealed, the second pass rolling deformation is carried out at the temperature of 280-340 ℃, and the strain rate of the rolling is 6.0-7.1s ‑1 . The preparation method of the layered double-scale magnesium alloy adopts high strain rate and gradient cooling double-pass rolling to obtain the high-toughness magnesium alloy material with a layered double-scale tissue structure, and the ultra-fine grain layer and the micron crystal layer are alternately layered and distributed, so that the strength and the plastic toughness of the magnesium alloy are improved.)

1. A preparation method of a layered double-scale magnesium alloy is characterized by comprising the following steps:

heating the magnesium alloy plate blank subjected to heating homogenization treatment at the temperature of 280-370 ℃ for 20-30min at the equal temperature, and immediately performing first-pass rolling deformation at the rolling strain rate of 3.5-4.9s^-1Obtaining a deformed plate;

after the deformation plate is annealed, the second pass rolling deformation is carried out at the temperature of 280-340 ℃, and the strain rate of the rolling is 6.0-7.1s^-1。

2. The method for preparing the layered double-scale magnesium alloy as recited in claim 1, wherein the temperature of the heating homogenization treatment is 400-440 ℃, and the heat preservation time is 12-16 h.

3. The method for preparing the layered double-scale magnesium alloy as recited in claim 1, wherein the annealing temperature of the annealing treatment is 280-340 ℃, and the annealing time is 30-60 min.

4. The method for preparing the layered double-scale magnesium alloy according to claim 1, wherein the linear speed of rolling in the first-pass rolling deformation and the second-pass rolling deformation is 15-18 m/min.

5. The method for preparing a layered double-scale magnesium alloy according to claim 1, wherein a reduction amount in the first pass rolling deformation is 30-40% of a height of the magnesium alloy slab.

6. The method of claim 1, wherein the reduction in the second pass rolling reduction is 50-60% of the height of the deformed sheet material.

7. The method for preparing the layered double-scale magnesium alloy according to claim 1, wherein the difference between the rolling temperature of the second-pass rolling deformation and the rolling temperature of the first-pass rolling deformation is 25-35 ℃.

Technical Field

The invention belongs to the field of light metal material processing, and particularly relates to a preparation method of a layered double-scale magnesium alloy.

Background

With the energy conservation and environmental protection becoming the subject of the modern times, magnesium and magnesium alloy have been widely applied to the fields of aerospace, rail transit, electronic products and the like due to the advantages of high specific strength, low density, good damping property and shielding property and the like, and the requirements on light weight of automobiles and the tension of energy resources greatly promote the development of magnesium alloy. With the increasing complexity of the service environment of engineering components, the requirements on the performance of magnesium alloys are higher and higher. However, magnesium alloys, which are the lightest metal structural materials used in engineering applications, have a typical close-packed hexagonal crystal structure, low stacking fault energy, few independent slip systems, and are likely to crack during low-temperature processing. At present, components of magnesium alloy are mainly cast, but cast magnesium alloy has the defects of looseness, shrinkage cavity, inclusion, microcrack and the like, so that the strength and the ductility and the toughness of the cast magnesium alloy are difficult to meet the industrial application requirements of the current times, and the application of the cast magnesium alloy in engineering is greatly limited. Therefore, a novel forming process method with high efficiency and low cost is urgently needed to prepare the magnesium alloy with excellent comprehensive mechanical properties, and the performance of the traditional magnesium alloy is improved, which has important significance for further expanding the industrial application range of the magnesium alloy.

The production method of the magnesium alloy mainly comprises two modes of casting forming and forging forming. The cast magnesium alloy has the defects of looseness, shrinkage cavity, inclusion, microcrack and the like, so that the strength and the plasticity and toughness of the cast magnesium alloy are poor; in contrast to cast magnesium alloys, forged magnesium alloys may undergo conventional plastic forming processes such as: extrusion, rolling, etc. or novel large plastic deformations such as: high-pressure torsion, equal-channel angular extrusion, reciprocating pier-extrusion and the like can effectively eliminate the internal structure defect of the material and obtain obvious refinement of a microstructure. The performances of the fine-grain magnesium alloy in various mechanical aspects are incomparable with those of the traditional coarse-grain materials, such as higher strength, hardness and wear resistance. However, when deformed at room temperature and under a large strain rate condition, the fine grain magnesium alloy has lower plasticity than the conventional coarse grain material.

The dual-scale structural alloy, namely the internal organization structure of the material is composed of two scale organization morphologies of a certain amount of coarse crystal, ultra-fine crystal or nano crystal, and the dual-scale alloy has the advantages of two composition scale organizations: the coarse grains have strong work hardening capacity, can resist deformation instability of the fine grains during plastic deformation, and improves the deformation stability and plasticity of the material; the formation of ultra-fine crystals or nano-crystals greatly increases the grain boundary area of crystal grains, and improves the capability of hindering dislocation migration, thereby showing the mechanical characteristics of high strength of the alloy. In summary, the material with double-scale structure has excellent plasticity and toughness and higher strength and hardness, thereby meeting increasingly demanding application requirements of engineering components.

At present, the magnesium alloy material with the double-scale structure is mainly prepared by a powder metallurgy and plastic deformation method. The powder metallurgy method is to mechanically mix two kinds of powder particles with crystal grains of different sizes and then perform solid state sintering to obtain a magnesium alloy block material. The plastic deformation method can introduce large strain in the deformation process, so that coarse crystals in the original blank are effectively refined, and a complete large-size block sample can be obtained. However, the regulation of the magnesium alloy forming process requires reasonable selection and even combination of plastic deformation process, and selection of appropriate deformation process parameters and whether to carry out heat treatment on the material, and the variation of the factors ensures that the property of the magnesium alloy regulated by the process is full of uncertainty.

Disclosure of Invention

The invention aims to provide a preparation method of a layered double-scale magnesium alloy, which adopts high strain rate and gradient cooling double-pass rolling to obtain a high-toughness magnesium alloy material with a layered double-scale organizational structure, and improves the strength and the ductility and the toughness of the magnesium alloy due to the alternate layered distribution of an ultra-fine grain layer and a micron crystal layer.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

a method of preparing a layered dual-scale magnesium alloy, comprising:

heating the magnesium alloy plate blank subjected to heating homogenization treatment at the temperature of 280-370 ℃ for 20-30min at the equal temperature, and immediately performing first-pass rolling deformation at the rolling strain rate of 3.5-4.9s^-1Obtaining a deformed plate;

after the deformation plate is annealed, the second pass rolling deformation is carried out at the temperature of 280-340 ℃, and the strain rate of the rolling is 6.0-7.1s^-1。

Further, in the preferred embodiment of the present invention, the temperature of the heating homogenization treatment is 400-440 ℃, and the heat preservation time is 12-16 h.

Further, in the preferred embodiment of the present invention, the annealing temperature of the annealing treatment is 280-340 ℃, and the annealing time is 30-60 min.

Further, in the preferred embodiment of the present invention, the linear speed of rolling in the first rolling deformation and the second rolling deformation is 15-18 m/min.

Further, in a preferred embodiment of the present invention, in the first rolling deformation, the reduction amount is 30 to 40% of the height of the magnesium alloy slab.

Further, in a preferred embodiment of the present invention, in the second pass rolling deformation, the reduction is 50-60% of the height of the deformed plate.

Further, in a preferred embodiment of the present invention, the difference between the rolling temperature of the second pass rolling deformation and the rolling temperature of the first pass rolling deformation is 25-35 ℃.

Compared with the prior art, the invention has the following beneficial effects:

because the magnesium alloy is a typical close-packed hexagonal crystal structure, and has low stacking fault energy and few independent slip systems, if a single-pass hot rolling method is adopted, the strain rate is high, and cracking and the like are easy to occur. In the traditional rolling process, in order to avoid cracking of the plate, small reduction and multi-pass hot rolling are generally adopted, and the method comprises an intermediate heat treatment process, so that the process is complex, the production efficiency is low, and the cost is high.

1. The preparation method of the layered double-scale magnesium alloy provided by the invention adopts high strain rate and gradient cooling double-pass rolling, so that the magnesium alloy plate with fine structure and excellent performance can be obtained, the rolling passes are reduced, the flow of an intermediate process is simplified, the production efficiency is high, and the market prospect of industrial application is wide.

2. The high strain rate rolling can introduce large strain amount into the cast magnesium alloy plate in a short time, a large amount of twin crystals can be generated in a deformation structure through the high strain rate, the structure is refined through the interaction between the twin crystals and the dynamic recrystallization in the twin crystals, stress concentration can be released to avoid rolling cracking, a dual-scale structure can be obtained, and the improvement of strength is facilitated.

3. The magnesium alloy plate can only bear the deformation of high strain rate through the continuous and rapid rheology of local areas by rolling deformation with high strain rate and large strain, and has obvious shear band in the magnesium alloy plate, and the superfine crystal structure in the shear band and the micron crystal structure in other areas form the alternate layered distribution of superfine crystal layers and micron crystal layers, thereby improving the strength and the plastic toughness of the magnesium alloy.

4. In the method, the strain rate of the first rolling is 3.5-4.9s^-1The strain rate of the second pass rolling is 6.0-7.1s^-1. The plate can be refined by coarse grains in the original structure through the first-pass rolling, which has the beneficial effect on the second-pass high strain rate rolling: on one hand, the material is softened and is not easy to generate stress concentration so as to crack; on the other hand, the plastic property of the plate is improved.

5. Before rolling the magnesium alloy plate blank, carrying out homogenization heating treatment on the magnesium alloy plate blank, which is beneficial to the dispersion distribution of the second phase in a matrix and the elimination of excessive coarse second phase distributed in the as-cast structure.

6. In the invention, the rolling reduction of the first pass rolling deformation is 30-40%, the rolling reduction of the second pass rolling deformation is 50-60%, which is beneficial to forming a double-scale structure of the magnesium alloy, and if the rolling reduction is too large, the magnesium alloy with a close-packed hexagonal structure is easy to crack or even split; on the contrary, if the rolling reduction is too small, the number of rolling passes is increased, and the production efficiency is reduced.

Drawings

FIG. 1 is a microstructure diagram of a magnesium alloy sheet produced in example 1 after finish rolling in a second pass;

FIG. 2 is a grain size distribution diagram of the magnesium alloy sheet produced in example 1 after the second pass of finish rolling;

FIG. 3 is a microstructure diagram of the magnesium alloy sheet produced in example 2 after the second pass of finish rolling;

FIG. 4 is a grain size distribution diagram of the magnesium alloy sheet produced in example 2 after the second pass of finish rolling;

FIG. 5 is a microstructure diagram of the magnesium alloy sheet produced in example 3 after the second pass of finish rolling;

FIG. 6 is a grain size distribution diagram of the magnesium alloy sheet produced in example 3 after the second pass of finish rolling; and

fig. 7 is a microstructure view of the magnesium alloy sheet prepared in comparative example 1.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The preparation method of the layered double-scale magnesium alloy provided by the invention is suitable for magnesium alloys of various specifications and models. In the embodiment, the alloy selected is cast AM60, and the alloy comprises, by weight, 5.6-6.4% of Al, 0.26-0.5% of Mn, 0.1-0.2% of Zn, 0.3-0.5% of Si, 0.002-0.004% of Fe, 0.001-0.008% of Cu, 0.0005-0.001% of Ni, and the balance of Mg and inevitable impurities, wherein the total weight of the impurities is less than or equal to 0.01%.

The features and properties of the present invention are further described in detail below with reference to examples: