Effect Of Extrusion And Heat Treatment On The Microstructure And Mechanical Property Of Mg-8Gd-3Y-0.4Zr Alloy

Optical microscope, scanning electron microscope, transmission electron microscope, X-Ray diffraction and mechanical tester were used to characterize the microstructure and mechanical property of the as-cast, homogenized, extruded, aged Mg-8Gd-3Y-0.4Zr(wt.%) alloy, the following results were obtained:1、As cast Mg-8Gd-3Y-0.4Z(wt.%) alloy contains αMg、Mg24(Gd,Y)5. Eutectic compounds contain Mg24(Gd,Y)5phase and αMg phase, and the cubic compound is Mg24(Gd,Y)5phase.2、460℃/6h+520℃/16h is the optimization of the homogenization. After homogenized, no eutectic compounds were found, and most Mg24(Gd,Y)5compounds were dissolved. The Y-rich compounds were found in the homogenized alloy.3、The β" phase was precipitated when the Mg-8Gd-4.8Y-0.4Zr (wt.%) alloy was extruded at380℃.4、With the extrusion enlarged, finer grains, higher strength and elongation to failure were obtained in the as extruded alloys. When extruded at380℃with the extrusion ratio of48, the alloy presents a yield strength of248MPa, an ultimate strength of333MPa, an elongation of12.1%.5、The maximum of the vikers micro hardness was obtained after the extruded Mg-8Gd-4.8Y-0.4Zr (wt.%) alloy was aged for21h at220℃. The strength of the peaked aged alloys was elevated about29-39%compared with the as extruded alloys. The highest yield strength is330MPa, with an ultimate strength of456MPa, yield strength of5.1%. β" phase and β’phase co-exit in the peak aged alloys.6、Ductile fracture dominates the fracture of the as-extruded alloy in the simple tension test at room temperature, while the brittle fracture dominate the fracture of the aged alloy.