Mg-12gd-3y-0.5zr (wt.%) Alloy Mechanical Properties And Deformation Twin Study

Lightweight magnesium alloys have attracted increasing interest in recent years for potential applications in the aerospace,aircraft and automotive industries due to their high strength/weight ratio. The poor plasticity at room temperature and difficulty for cold working restrain the development and application of magnesium.Mg-base alloys with rare-earth metals are becoming more and more attractive due to their high strength and creep resistance.In this paper,Mg-12Gd-3Y-0.5Zr(wt.%) alloy, which exhibits excellent mechanical properties, was researched. Strengthening techniques including hot extrusion(Ex), hydrostatic extrusion at room temperature(H.Ex), aging at 250℃for 48h, solid solution(S.S) treatment at 525℃were applied to the Mg-12Gd-3Y-0.5Zr(wt.%) alloy. The mechanical properties were tested by the tensile and compress testing along the extrusion direction, and the microstructure has been investigated using optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that high strength is achieved by Ex+H.Ex+Aging,whose ultimate tensil strength(UTS) is 390 MPa.Precipitation strengthening (σppt≈92MPa) and grain boundary strengthening (σgb≈72MPa) are the two main contributions to the high UTS. Precipitions prone to genterate along grain boundary , twin boundary and dislocation cells , that result in poor ductility. After hot extrusion both the yield tensile strength(YTS) and elongation increase when the hydrostatic extrusion ratio elevates,because of the strong base plan texture is weakened and broken up by H.Ex. So, hydrostatic extrusion at room temperature is considered to be an effective method used to improve the mechanical properties of Mg-12Gd-3Y-0.5Zr(wt.%) alloy.Many (?) deformation twinnings and dislocations are observed in hot extruded materials. The analysis shows that the rare-earth elements and precipitions inhibit (?) deformation twinnings. (?) deformation twinnings are observed after Ex, S.S and H.Ex treatment. (?) twinning ratio and twinning area fraction increas with the growing hydrostatic extrusion ratio. It has been shown that (?) twinning coincide with low temperature,coarse grain and high stress.