Al_2O_3-SiO_(2(sf))/AZ91D镁基复合材料蠕变本构方程

利用常应力拉伸蠕变试验法对体积分数为25%的硅酸铝短纤维(Al2O3-Si O2(sf))增强AZ91D镁基复合材料及其基体合金AZ91D在温度为473 K和573 K、外加应力为30～100 MPa下进行蠕变测试。根据应变和应变速率曲线,计算出复合材料的真应力指数、真蠕变激活能、真门槛应力、载荷转移因子和蠕变本构方程。TEM分析结果表明,复合材料蠕变后的门槛应力来源于短纤维表面上的MgO颗粒和Mg17Al12析出相对可动位错的钉扎作用,短纤维具有承载和传递载荷作用,从而提高了复合材料的抗蠕变性能。

Creep constitutive equation of Al2O3-SiO2(sf)/AZ91D magnesium matrix composite

Constant stress tensile creep tests were conducted on the 25vol% Al2O3SiO2 short fiber/AZ91D composite and the unreinforced AZ91D matrix alloy at 473K and 573K under the applied stresses of 30~100MPa. The true stress exponent, the true creep activation energy, the threshold stress and the creep constitutive equation of the composite were calulated according to the curves of strain and strain rate. Microstructural investigations by TEM reveal that the threshold stress of the composite results from the pinning effect of MgO particles and Mg17Al12 precipitation on the fiber surface on the movable dislocations during creep exposure. Short fibers have a great function in load bearing and load transfer, and result in the enhancement of the creep resistance of the composite.