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The microstucture,mechanical properties and fracture behaviors of semi-continuous cast Mg-8Gd-3Y-0.5Zr(wt.%,GW83K) alloy after different heat treatments were investigated.Almost all the eutectic compounds were dissolved into the matrix and there was no evident grain growth after optimum solution treatment at 500 ℃for 4h.Further ageing at low temperatures led to significant precipitation hardening,which strengthened the alloy.Peak-aged at 200 ℃,the alloy had the highest ultimate tensile strength(UTS) and lowest elongation at 395 MPa and 2.8%,respectively.When aged at 225 ℃ for 15 h,the alloy exhibited prominent mechanical performance with UTS and elongation of 363 MPa and 5.8%,respectively.With regard to microstructure and tensile properties,the processes of 500 ℃,4h+225℃,15 h are selected as the optimal heat treatment conditions.The alloy under different conditions shows different fracture behaviors:in the as-cast alloy,a quasi-cleavage pattern is observed;after solution treatment,the alloy exhibits a trans-granular quasi-cleavage fracture;after being peak-aged at 200 ℃ and 225 ℃,the fracture mode is a mixed mode of trans-granular and intergranular fracture,in which the inter-granular mode is dominant in the alloy peak-aged at 200 ℃.
The microstucture, mechanical properties and fracture behaviors of semi-continuous cast Mg-8Gd-3Y-0.5Zr (wt.%, GW83K) alloy after different heat treatments were investigated. Almost all the eutectic compounds were dissolved into the matrix and there was no The grain had after optimum solution treatment at 500 ° C for 4h.Further aging at low temperatures led to significant precipitation hardening, which strengthened the alloy. Peak-aged at 200 ° C, the alloy had the highest ultimate tensile strength (UTS) at 395 MPa and 2.8%, respectively.When aged at 225 ° C for 15 h, the alloy exhibited prominent mechanical performance with UTS and elongation of 363 MPa and 5.8%, respectively.With regard to microstructure and tensile properties, the processes of 500 ° C , 4h + 225 ° C, 15 h are selected as the optimal heat treatment conditions. The alloy under different conditions shows different fracture behaviors: in the as-cast alloy, a quasi-cleavage pattern is observed; after solution trea tment, the alloy exhibits a trans-granular quasi-cleavage fracture; after being peak-aged at 200 ° C and 225 ° C, the fracture mode is a mixed mode of trans-granular and intergranular fracture, in which the inter-granular mode is dominant in the alloy peak-aged at 200 ° C.