热挤压AZ31镁合金的组织结构与蠕变行为

通过对热挤压态AZ31镁合金进行组织形貌观察、内摩擦应力测定及蠕变性能测试,研究了热挤压AZ31合金的组织结构和蠕变行为.结果表明:热挤压AZ31镁合金的组织具有带状结构特征,并沿轧制方向分布,且有β-Mg17Al12相在合金中弥散析出.蠕变期间,位错运动的内摩擦力有较强的温度敏感性,随温度增加,内应力值明显降低,致使合金具有较高的蠕变速率.合金在蠕变期间,大量位错的形成与运动是蠕变初期的变形机制;蠕变稳态阶段,高密度位错逐渐束集形成位错胞,进一步发生蠕变期间的动态再结晶.随裂纹在晶界处萌生使蠕变进入第三阶段,而裂纹沿晶界韧性撕裂扩展是合金的蠕变断裂机制.

Microstructure and creep behaviors of hot extrusion AZ31 magnesium alloy

By means of microstructure observation,internal frictional stress and creep properties measurement,an investigation has been made into the microstructure and creep properties of hot extraction AZ31 alloy.Results show that the microstructure of hot extruded AZ31 alloy possesses strip-like feature which distribute along the extruded direction,and the β-Mg17Al12 particles are dispersedly precipitated in the alloy.During creep,the internal frictional stress values of dislocation movement possess an obvious sensitivity on the applied temperature,and the value of internal frictional stress decrease as the temperature increases,which result in the alloy possessing larger strain rate during creep at high temperature.Significant amount of dislocations activated in the alloy is thought to be the main deformed mechanism in the initial stage of creep.During steady state creep,the denser dislocations are concentrated to form the cells structure,and gradually transformed into the fine subgrain structure due to the occurrence of the dynamic recrystallization.Once the micro-cracks initiate along the grain boundary,the creep of the alloy turns into the tertiary stage.As creep goes on,the cracks are viscously propagated along the boundary,which is thought to be the fracture mechanism of the alloy during creep.