Internal stress relaxation and load redistribution during the twinning–detwinning-dominated cyclic deformation of a wrought magnesium alloy, ZK60A
Internal stress relaxation and load redistribution during the twinning–detwinning-dominated cyclic deformation of a wrought magnesium alloy, ZK60A
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DOI：
10.1016/j.actamat.2008.04.006
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发表时间：
2008-08
期刊：
影响因子：
9.4
通讯作者：
L. Wu;S. Agnew;D. Brown;G. M. Stoica;B. Clausen;A. Jain;D. Fielden;P. Liaw
中科院分区：
文献类型：
--
作者：
L. Wu;S. Agnew;D. Brown;G. M. Stoica;B. Clausen;A. Jain;D. Fielden;P. Liaw
利用原位中子衍射研究了镁合金 ZK60A 中以{101´2}<101´1>孪生和解孪机制为主的循环变形过程中的内应变（应力）演变。结果表明，一旦基体晶粒孪晶，(00.2) 基体和孪晶晶粒相对于相邻晶粒就会松弛。软晶粒取向和硬晶粒取向之间的这种载荷重新分布是塑性各向异性的结果。当卸载时施加的压应力小于~80MPa时，在初始压缩过程中形成的孪晶沿c轴承受拉应力。假设这种局部（晶间）拉伸应力可有效驱动沿 c 轴的宏观压缩场下的解孪事件。基于基体和孪晶晶粒中内应力的松弛，{101´2}<101´1>延伸孪晶和解孪的激活应力分别为 15 和 6MPa。
A study of the internal strain (stress) evolution during cyclic deformation dominated by {101¯2}〈101¯1〉 twinning and detwinning mechanisms within a magnesium alloy, ZK60A, was conducted using in situ neutron diffraction. It is shown that once the matrix grains twin, the (00.2) matrix and twin grains are relaxed relative to the neighbors. This load redistribution between the soft- and hard-grain orientations is a result of plastic anisotropy. The twins which formed during the initial compression sustain a tensile stress along the c-axis, when the applied compressive stress is less than ∼80MPa upon unloading. This local (intergranular) tensile stress is hypothesized to be effective for driving the detwinning event under a macroscopic compressive field along the c-axis. The activation stresses, 15 and 6MPa, respectively, for the {101¯2}〈101¯1〉 extension twinning and detwinning, are approximated, based on the relaxation of the internal stresses in the matrix and twin grains.