摘要
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 ~C for 4 h. 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℃, 4 h ＋ 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 inter-granular 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 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 ℃.
基金
financially supported by the National Natural Science Foundation of China(51074106)
the National Key Technology R&D Program of China(2011BAE22B01-5)
