Solidification Microstructure and Properties of Mg-4Al-0.5Me Alloys Cast by Graphite Crucible

The solidification structure and properties of Mg-4Al-0.5Me (Nd, Y, Ca) alloys cast by graphite crucible were studied by SEM, EDS and XRD.The results show that the solidification structure of the alloys is mainly composed of α-Mg and β-Mg₁₇Al₁₂.The structure of Mg-4Al-0.5Nd and Mg-4Al-0.5Y alloys is coarse and has granular phase precipitated along the grain boundary.After adding a small number of Ca element to Mg-4Al, the structure is effectively refined.The micro-hardness of Mg-4Al-0.5Nd and Mg-4 Al-0.5Y alloy is 50.78 HV and 50.82 HV, respectively.The micro-hardness of Mg-4Al-0.5Ca alloy is significantly improved to 60.8 HV.The pressure strength of the three alloys is 330.14 MPa, 334.56 MPa and 361.77 MPa, respectively.