The microstructural evolution of the Mg-6Y-3Gd-3Zn-0.5Zr alloys in the as-cast,solid solution and aging states and its influence on the mechanical properties were investigated by using OM,SEM,XRD,TEM and property testing methods.The results show that the as-cast alloy consists of dendritic α-Mg matrix with a continuous network of 18R-LPSO and Mg24(Gd,Y,Zn)5 mixed phases at the grain boundaries.After solid solution treatment,the most of Mg24(Gd,Y,Zn)5 phase and part of the 18R-LPSO phase are dissolved back into the matrix.A large amount of lamellar 14H-LPSO and Mg3(Y,Gd)and Mg5(Y,Gd)phases are precipitated in the matrix after aging at 250 ℃and 300 ℃.Only 14H-LPSO phase is precipitated in the crystals after aging at 400 ℃.The tensile strength and elongation of the as-cast alloy are 222.7 MPa and 4.1％,respectively.The strength of the alloy decreases and the elongation increases slightly after aging.The alloy peak aged at 400 ℃ shows the greatest decrease in strength due to the large number and size of 14H-LPSO precipitated in the crystals,and the tensile strength decreases by 39 MPa compared with that of the as-cast state.
NETL
NSTL
万方数据
