高应变速率下AZ31镁合金的力学性能和微观组织演变

发布时间：2018-06-25 00:54

本文选题：各向异性 + 加工硬化　；参考：《重庆大学》2016年硕士论文

【摘要】：本文选用具有典型基面织构的商用AZ31热轧板,设计了七类不同初始取向的圆柱样品,取其压缩轴(LD)与板材的法向(ND)分别成0°,15°,30°,45°,60°,75°和90°,在不同的应变速率(10-3和103量级)下进行单轴压缩实验,利用金相和电子背散射衍射(EBSD)技术定量表征指定变形量的样品组织。本研究中的高应变速率变形是通过霍普金森压杆技术实现的。通过分析高应变速率变形的应力应变曲线,讨论了AZ31镁合金在高应变速率下变形的各向异性和加工硬化现象;并通过与低应变速率下的变形进行比较,讨论了应变速率敏感性。得出了以下主要结论:1、不同取向AZ31镁合金在高应变速率变形下的力学性能表现出强烈的各向异性;2、在孪晶为主导变形机制的45°、60°、75°和90°取向中,加工硬化第二阶段与孪晶同步进行,在指定变形量下的完成率几乎相同;3、0°取向在高应变速率下具有更高的屈服强度,30°-90°取向在高应变速率下屈服强度几乎不变。采用金相和EBSD技术对AZ31镁合金高应变速率下的变形组织进行表征,讨论了样品孪晶行为、剪切带等微观组织演变,并通过与低应变速率下的孪晶形貌进行比较,讨论了孪晶形核与长大的竞争。得出了以下主要结论:1、0°和15°取向AZ31镁合金,在高应变速率变形中形成了明显的剪切带;2、对45°、60°、75°和90°这四种由孪生主导塑形变形的取向,在高应变速率时,{10-12}拉伸孪晶变体的选择规律基本上符合Schmid法则,但与低应变速率相比,高应变速率时更有利于孪晶形核;3、0°取向剪切带组织中有少量孪晶和大量滑移发生,其中的基面滑移具有最大的SF,与基面滑移之间的协调作用可能为孪生发生提供驱动力。
[Abstract]:In this paper, commercial AZ31 hot rolled plates with typical basal texture are selected and seven kinds of cylindrical samples with different initial orientations are designed. Taking the normal direction (ND) of compression axis (LD) and plate as 0 掳/ 15 掳/ 30 掳/ 45 掳/ 60 掳/ 60 掳/ 75 掳and 90 掳respectively, uniaxial compression experiments were carried out at different strain rates (10 ~ (-3) and 10 ~ (-3). The microstructure of samples with specified deformation was quantitatively characterized by metallography and electron backscattering diffraction (EBSD). The high strain rate deformation in this study is realized by the Hopkinson pressure bar technique. By analyzing the stress-strain curve of high strain rate deformation, the anisotropy and work hardening of AZ31 magnesium alloy at high strain rate are discussed, and the strain rate sensitivity is discussed by comparing the deformation at low strain rate with that of AZ31 magnesium alloy at high strain rate. The main conclusions are as follows: 1. The mechanical properties of AZ31 magnesium alloys with different orientations show strong anisotropy under high strain rate deformation. In the twinning orientation of 45 掳, 60 掳, 75 掳and 90 掳, the second stage of work hardening is synchronized with the twin. The yield strength of 30 掳-90 掳orientation at high strain rate is almost unchanged at high strain rate. The microstructure of AZ31 magnesium alloy at high strain rate was characterized by metallography and EBSD. The twinning behavior and shear band evolution of AZ31 magnesium alloy were discussed and compared with those at low strain rate. The competition between twin nucleation and growth is discussed. The main conclusions are as follows: 1 0 掳and 15 掳orientation of AZ31 magnesium alloy formed obvious shear band in high strain rate deformation, and the four twinning orientations of 45 掳~ 60 掳~ 75 掳and 90 掳were formed. At high strain rate, the selection rule of {10-12} tensile twin is basically in accordance with Schmid's rule. However, compared with low strain rate, high strain rate is more favorable to the formation of a small amount of twins and a large number of slippages in the structure of the twinning nucleation 30 掳orientation shear band. Among them, the base slip has the largest SF. and the coordination between the base slip and the base slip may provide the driving force for the twinning.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG146.22

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