Twinning, Detwining and Fatigue Crack Initiation in Extruded Magnesium Alloy AZ31
Twinning, Detwining and Fatigue Crack Initiation in Extruded Magnesium Alloy AZ31
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挤压镁合金 AZ31 中的孪生、解缠和疲劳裂纹萌生
DOI：
10.1016/j.msea.2021.141941
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Hayata Yoshida
中科院分区：
文献类型：
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作者：
Yoshikazu Nakai;Shoichi Kikuchi;Kaito Asayama;Hayata Yoshida
几种类型的循环应力施加到由挤压镁合金AZ 31制成的试样上，通过电子背散射衍射分析来阐明孪晶、去孪晶和疲劳裂纹萌生机制。在织构和随机取向中，在超过压缩屈服强度的压缩应力下发生孪生。解孪晶只发生在随后施加的拉伸应力小于单调加载的拉伸屈服强度的纹理，而解孪晶没有发生在随机取向的结构。在压-压疲劳试验中，连续孪生发生，改变了基面的取向。结果，晶粒的随机取向转变为基面法线平行于加载方向的织构。裂纹沿着晶界形成，晶界处的滑移系Schmid因子较高，两侧晶粒错配较大。在裂纹萌生点附近，观察到孪晶带;然而，在循环压缩载荷后的拉伸应力下，没有发生解孪晶。
Several types of cyclic stress were applied to specimens made of an extruded magnesium alloy, AZ31, to elucidate twinning, detwinning, and fatigue crack initiation mechanisms by electron backscattered diffraction analysis. In both the texture and the random orientation, twinning occurred under compressive stress exceeding the compressive yield strength. Detwinning occurred only in the texture upon the subsequent application of tensile stress less than the tensile yield strength of monotonic loading, whereas detwinning did not occur in the structure with random orientation. Under compression–compression fatigue test, successive twinning occurred, which changed the orientation of the basal plane. As a result, the random orientation of grains changed to the texture in which the normal of the basal plane was parallel to the loading direction. Cracks were formed along the boundary of grains with a high Schmid factor of the basal slip system and the misfit of grain on both sides was large. Near the crack initiation site, twin bands were observed; however, detwinning did not occur under the tensile stress after the cyclic compression loading.