ZK60镁合金塑性变形行为的实验与模拟研究

发布时间：2017-12-28 08:01

本文关键词：ZK60镁合金塑性变形行为的实验与模拟研究　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文选用具有强烈基面织构的固溶态及时效态ZK60镁合金板材,从不同方向对材料进行拉伸压缩变形。利用金相实验、电子背散射衍射(EBSD)等实验手段对镁合金的微观组织进行了表征。同时本文借助晶体塑性理论对材料变形的微观机制进行了模拟,重点研究了固溶及时效对材料变形的各向异性及拉压不对称性的影响,得到如下结论:①固溶态ZK60镁合金在175℃进行时效处理10h之后,材料的基面织构得到了保留,但由于析出相的引入,材料沿不同方向变形的强度有着不同程度的提高。利用VPSC粘塑性自洽模型,可以完美拟合固溶态和时效态镁合金沿不同方向拉伸压缩过程中的应力-应变曲线。②当沿轧板面RD方向进行拉伸时,固溶态和时效态的主导变形机制为基面滑移和柱面滑移。利用VPSC模拟材料的r值,发现时效处理后,材料的平均r值下降,试样沿厚度方向的变形能力得到了提高,其主要原因在于时效处理抑制了柱面滑移的启动,但是却促进了基面滑移的启动,因此会导致晶体产生不同程度的转动,进而影响到锥面c+a滑移在两种状态材料中的启动量。③ZK60镁合金在不同方向变形的织构演变差异主要来自于其微观启动机制的不同,时效处理不改变材料的主导变形机制,因而固溶态和时效态材料的织构演变规律是相同的。但是,模拟结果表明时效处理会促进压缩孪晶以及二次压缩孪晶的启动,因而90°压缩和0°压缩样的织构产生了差异。④时效处理可以强化材料在屈服变形中各个主导变形机制,因而时效处理同时提高了材料拉伸和压缩的屈服应力。但是由于时效处理对不同主导变形机制的强化程度不一样,故材料的拉压不对称性提高。⑤时效态ZK60材料在沿RD压缩过程中,其主导变形机制为{10-12}拉伸孪生和基面滑移,时效处理虽然会提高孪晶的启动应力,但是却不会影响在塑性变形过程中孪晶的长大。由于{10-12}拉伸孪生的临界剪切应力CRSS远远低于启动柱面滑移所需要的CRSS,所以ZK60镁合金在屈服过程中表现出来明显的拉压不对称性。
[Abstract]:In this paper, a solid solution state ZK60 magnesium alloy plate with strong solid surface texture is used to stretch and compress the material from different directions. The microstructure of magnesium alloy was characterized by means of metallographic experiment, electron backscatter diffraction (EBSD) and other experimental methods. At the same time the crystal plasticity theory to simulate the micro mechanism of deformation of the material with the help of solid solution and aging on anisotropic material deformation and the effect of tension compression asymmetry. The conclusions are as follows: 1. After solid solution aging treatment of ZK60 magnesium alloy 10h at 175 DEG C, basal texture of materials has been reserved, but due to the introduction of the precipitates, the material deformation strength along different directions have different degrees of improvement. By using the VPSC viscoplastic self consistent model, the stress-strain curves of the solid and aging magnesium alloys in the compression process in different directions can be fitted perfectly. The dominant deformation mechanism of the solid solution and the aging state is the base slip and the cylindrical slip when the RD direction is stretched along the rolled plate. Using VPSC to simulate the R value of the material, it was found that the aging treatment, the average R values decreased, the deformation ability of specimens along the thickness direction has been improved, the main reason is that the aging treatment inhibited the prismatic slip start, but promote the basal slip start, thus causing crystal rotation in different degree, and to start the amount of c+a in the two cone slip state of the material in the. (3) the difference of texture evolution of ZK60 magnesium alloy in different directions is mainly due to the different starting mechanism. Aging treatment does not change the dominant deformation mechanism of the material, so the texture evolution law of solid solution and aging material is the same. However, the simulation results show that aging treatment will promote the initiation of compressive twinning and the two compression twinning. Therefore, the texture of 90 degree compression and 0 degree compression sample is different. 4. Aging treatment can strengthen the main deformation mechanism of the material in the yield deformation, so the aging treatment improves the yield stress of the tensile and compression of the material. However, due to the different strengthening degree of aging treatment on different dominant deformation mechanisms, the tensile and pressure asymmetry of the material is increased. The main deformation mechanism of aging ZK60 materials is RD tensile twinning and base slip. The aging treatment will improve the starting stress of twins, but it will not affect the growth of twins in plastic deformation process. Because the critical shear stress CRSS of {10-12} twinning is far lower than the CRSS required for starting cylinder slip, ZK60 magnesium alloy exhibits obvious tension compression asymmetry during yielding.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.22;TG166.4

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