MgCO3对AZ81镁合金晶粒的细化行为及影响机制

Effect of MgCO3 on grain refinement of AZ81 magnesium alloy and its mechanism

添加不同量的MgCO3对AZ81镁合金进行晶粒细化实验,结果表明:MgCO3对AZ81镁合金细化效果明显,当加入量w(MgCO3)=1.2%时,合金晶粒最小;随后继续增加MgCO3加入量,晶粒又开始变粗大。经X射线衍射发现MgCO3加入后,合金中出现新的Al4C3相;经计算,Al4C3与α-Mg晶格常数相近,晶粒错配度小,Al4C3成为α-Mg基底的异质形核质点从而细化晶粒。

The grain refinement test of AZ81 magnesium alloy was carried out by adding different amount of MgCO3 . The results show that MgCO3 has obvious effect on the refinement of AZ81 magnesium alloy. When w( MgCO3 )= 1.2%,the grain size of the alloy is the smallest. As the amount of MgCO3 continues to increase subsequently,the grain is turning coarse again. It is found by X-ray diffraction that a new Al4C3 phase appears with addition of MgCO3 into the alloy. The calculation indicates that the lattice constants of Al4C3 and α-Mg are close to each other and their grain misfit is small. Al4C3 becomes a heterogeneous nucleated particle in α-Mg substrate,thus refining the grain.