原位自生Mg_2Si/Mg基复合材料的高温蠕变行为

Microstructure and Creep Behavior at High Temperature of In-situ Mg_2Si/Mg Composite

采用原位自生技术制备出不同Mg2Si含量的Mg2Si/Mg复合材料,利用光学显微镜观察其铸态组织,进一步研究了原位自生Mg2Si/Mg复合材料在不同温度和应力下的高温蠕变行为。结果表明,随着Si含量的增加,初生Mg2Si相从原来的块状向树枝状和花瓣状转变,分布在α-Mg和汉字状的共晶Mg2Si之间。原位自生Mg2Si/Mg复合材料的高温蠕变性能随着Mg2Si含量的增加而得到明显地提高,根据蠕变幂率方程,可求得材料的蠕变应力指数和表观激活能。该材料的蠕变表观应力指数均大于5,蠕变表观激活能大于纯Mg的蠕变激活能,且这2个参数在一定的条件下随着Mg2Si含量的增加而变大。该复合材料的蠕变机制主要是由位错攀移和第二相增强机制控制。

The Mg2Si/Mg composite, which contains the various content of Mg2Si, was prepared by in-situ technology. The morphology of the primary Mg2Si was observed by optical microscope, and the creep behaviors of the. prepared composite under different temperature and stress were analyzed. The results show that the morphology of the primary Mg2Si changes from block shape to dendritic or petaliform shape with the increase of Mg2Si, and the MgESi phases distribute around the α-Mg and the Chinese eutectic Mg2Si. The creep resistance of the composites increases obviously with the increase of Mg2Si. According to the creep power exponent equation, the creep apparent stress exponent and the creep apparent activation energy can be calculated. It is founded that both of them get larger with the increase of the Mg2Si content. Moreover, the creep apparent stress exponents are all over 5, while the creep apparent activation energy is higher than the pure Mg （134 kJ/mol）. The creep mechanism ofin-situ Mg2Si/Mg composite is probably deem as the dislocation climbing and the second phase strengthing.