Study On The Micro Structure And Properties Of Magnesium Alloys With The LPSO Structure Phase

Mg-Gd-Y magnesium alloy exhibits excellent mechanical properties, but because of its high manufacturing cost adverse for universal application. Therefore, under the premise of ensuring the mechanical performance advantage, reducing the rare earth elements content and studying on some new alloy become one of the key development directions in Mg-RE alloys. Accordingly, this paper based on Mg-6Gd-3Y-0.5Zr alloy which Gd:Y mole ratios of1:1with constant Gd+Y content of9wt%, through adding1%,2%,3%of Zn element get long period stacking order (LPSO) structure strengthen phase. Investigate effect of solid solution and deformation process on the microstructure and mechanical of these alloys. And also study the effect of LPSO structure phase on the microstructure and mechanical of alloys.The results show that X-Mg12(Y, Gd)Zn phase with LPSO structure is observed in the cast Zn-containing alloys. With the increasing of Zn addition, the volume of X-Mg12(Y, Gd)Zn phase first increase and then decrease. During heat-treatment at500°Cxl6h, Mg5(Gd,Y) phase which distributing along the grain boundary dissolves into the matrix, LPSO structure phase come into being, namely happen β-X phase transition process. In addition, after500°CX64h solid solution heat-treatment Mg-6Gd-3Y-2Zn-0.5Zr alloy grain size not grow up, LPSO structure phase unable to dissolve into the matrix. During540°CX64h solid solution heat-treatment, LPSO structure phase which distributing along the grain boundary shows disappearing process with time prolonging. At the same time a new straight lamellar LPSO structure phase throughout the grain.In order to further investigate the effect of LPSO structure phase on the deformation behavior of Mg-6Gd-3Y-2Zn-0.5Zr alloy, the alloy after500°CxlOh homogenization treatment was treated by hot extrusion and rolled treatment. After450°C hot extrusion, dynamic recrystallization occurs during hot extrusion, LPSO structure phase distributes along to the extrusion streamlined direction, LPSO structure phase has good plasticity, hot extrusion promoted the formation of LPSO structure phase. At ambient temperature, as-extruded Mg-6Gd-3Y-2Zn-0.5Zr alloy exhibits high strength and good ductility, and the value of ultimate tensile strength and yield tensile strength are335MPa and276MPa, respectively, companied with an elongation of17%. After450°C rolling deformation can obtain complete and no crack plank. LPSO structure phase is bent and distributes along to the streamlined direction, at the same time, straight lamellar LPSO structure phase forms from Mg matrix. The rolled Mg-6Gd-3Y-2Zn-0.5Zr alloy with good comprehensive mechanical property with the ultimate tensile strength of340MPa and yield tensile strength of264MPa, companied with an elongation of12.3%.