Mg-5Sn合金中析出相取向演变及其对合金热导率的影响

Evolution of precipitate orientation and its effect on thermal conductivity of Mg−5Sn alloy

系统研究Mg-5Sn合金在不同处理条件下析出相取向的演变及其对合金热导率的影响。结果表明,在先时效后孪生处理的合金(样品AT)中,基面析出相被调整为柱面析出相,并且板条状析出相发生3.7°的刚性转动以协调孪晶剪切;而样品AT中厚度较大的六边形析出相则只发生了0.2°的刚性转动,这是由于堆垛层错能够释放部分析出相/孪晶界的应变。此外,析出相的取向显著影响合金的热导率。当热导率测试方向平行于挤压方向时,与平行于挤压方向的柱面析出相相比,垂直于挤压方向的基面析出相更有利于合金热导率的提高。基面有析出相的TA(先孪生后时效处理)样品具有最佳的热导率(137.81 W/(m·K))。

The evolution of precipitate orientation and its effect on the thermal conductivity of Mg−5Sn alloys under different treatments were systematically investigated.The results show that for the alloy subjected to aging prior to twinning(Sample AT),the basal precipitates are precisely regulated to be the prismatic precipitates,and the lath-shaped precipitates experience a rigid rotation of 3.7°to accommodate the twinning shear.For hexagon-shaped precipitates with a larger thickness in Sample AT,the precipitate only experiences a small rigid rotation of 0.2°,due to the development of stacking faults releasing part of the strain at the precipitate/twin interface.In addition,the orientation of precipitates has a significant effect on the thermal conductivity of the alloy.When the measurement direction of thermal conductivity is parallel to extrusion direction(ED),the precipitates lying on the basal plane,perpendicular to ED,are more beneficial to the improvement of thermal conductivity than precipitates lying on the prismatic plane parallel to ED.Sample TA(aging after twinning)with precipitates lying on the basal plane shows the best thermal conductivity of 137.81 W/(m×K).