晶粒尺寸和晶界取向差对织构AZ31镁合金疲劳裂纹萌生机制的影响
Influence of grain size and grain boundary misorientation on the fatigue crack initiation mechanisms of textured AZ31 Mg alloy
摘要：
研究了织构AZ 31 B-O镁合金沿轧制方向进行完全反向应变控制循环变形50次（约为疲劳寿命的33%）后的变形和裂纹萌生机制。在2100个晶粒中，有538个晶粒出现明显的变形带，对应于锥体滑移或拉伸孪晶。滑移痕迹分析表明，72.3%为锥体滑移带，18.4%为孪晶界。在9.1%的变形带晶粒中，同时存在锥滑移和孪晶。50次循环后，裂纹普遍存在。在约15%的小晶粒（< 20 $μ$ m）中发现晶界裂纹，并且它们主要与高角度晶界（>40度）相关联。在大晶粒（>45 $μ$ m）中，平行于锥体滑移带或孪晶界的穿晶裂纹也会产生裂纹。这些大晶粒中的大多数（>60%）在50次循环后呈现穿晶裂纹。
英文摘要：
The deformation and crack initiation mechanisms were analyzed in a textured AZ31B-O Mg alloy subjected to fully-reversed, strain-controlled cyclic deformation along the rolling direction after 50 cycles (approximately 33% of the fatigue life). Distinct deformation bands corresponding to pyramidal slip or tensile twins were found in 538 grains out of 2100 grains. Slip trace analysis showed that 72.3% were pyramidal slip bands and 18.4% were twin boundaries. Both pyramidal slip and twinning was only found in 9.1% of the grains with deformation bands. Cracking was widespread after 50 cycles. Grain boundary cracks were found in approximately 15% of the small grains (< 20 $μ$m) and they were mainly associated with high angle grain boundaries (>40 degrees). Cracking was also found to occur by transgranular cracks parallel to the pyramidal slip bands or twin boundaries in large grains (>45 $μ$m). The majority (>60%) of these large grains presented transgranular cracks after 50 cycles.
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