Anisotropic degradation behavior of moduli of extruded pure magnesium during low cyclic-tension fatigue
Anisotropic degradation behavior of moduli of extruded pure magnesium during low cyclic-tension fatigue
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低周张力疲劳过程中挤压纯镁模量的各向异性退化行为
DOI：
10.1088/1742-6596/843/1/012026
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
H. Yamagishi
中科院分区：
文献类型：
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作者：
大西 航助;朱 世杰;安池 俊也，高橋 剛，福地 孝平;岡根正樹，清水貴明，安井利明，福本昌宏;H. Yamagishi
采用纵波和横波的超声反射方法，研究了挤压纯镁在挤压和横向加载方向下的室温低周拉疲劳力学性能，以澄清挤压方向之间是否存在各向异性的退化行为。在不考虑LD的情况下，随着循环次数的增加，声速以及计算得到的杨氏模量和剪切模量都显著下降，这是由于晶界和孪晶界处空隙的增大。结果表明：当偏转面在LD方向上排列时，模量的减少量大于横向排列时（TD）。此外，当调整应力幅值以提供相同的破坏循环次数时，当LD平行于挤压方向时，模量的下降幅度略大于与TD平行时。利用基于场发射扫描电镜（FE-SEM）的电子背散射衍射（EBSD）对疲劳后的晶界和孪晶界进行了纵向和SW传播特性的研究，结果表明，大多数空隙宽度小于几纳米（几乎闭合），与纵波振幅相对应。通过x射线衍射（XRD）、光学显微镜（OM）、扫描电镜（SEM）和维氏硬度测试获得了其他损伤相的数据；各向异性降解行为主要是由孔隙形态和取向的微小差异引起的。
The mechanical properties of extruded pure magnesium during low cyclic-tension fatigue at room temperature were investigated in the extrusion and transverse loading directions (LDs) using ultrasonic reflection methods with longitudinal and shear waves (SWs), to clarify if there was an anisotropic degradation behavior between the extruded directions (EDs), which had not yet revealed. Regardless of the LD, the acoustic velocities and calculated Young's and shear moduli decreased significantly with an increasing number of cycles because of the growth of voids at the grain and twin boundaries. An anisotropic behavior was revealed: when the deflection surface of the SWs was aligned in the LD, the amount of decrease in the moduli was greater than when the alignment was in the transverse direction (TD). Additionally, when the stress amplitude was adjusted to provide the same number of cycles to failure, the decrease in the moduli was somewhat greater when the LD was parallel to the extruded direction than to the TD. Longitudinal and SW propagation characteristics, and investigations of grain and twin boundaries after fatigue using electron backscatter diffraction (EBSD) based on field-emission scanning electron microscopy (FE-SEM), revealed that the most of the void-gap width was less than several nanometers (almost closed), which corresponded to the longitudinal wave amplitude. Other damaged-phase data were obtained using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and Vickers-hardness test; the anisotropic degradation behaviors were attributed to the void morphology and the slight difference in orientation.