论文部分内容阅读
The microstucture, mechanical properties and fracture behaviors of semi-continuous cast Mg-8Gd-3Y-0.5Zr (wt.%, GW83K) al oy after different heat treatments were investigated. Almost al 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 signiifcant precipitation hardening, which strengthened the al oy. Peak-aged at 200 °C, the al oy had the highest ultimate tensile strength (UTS) and lowest elongation at 395 MPa and 2.8%, respectively. When aged at 225 °C for 15 h, the al oy 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, 4 h+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 treatment, 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 inter-granular fracture, in which the inter-granular mode is dominant in the alloy peak-aged at 200 °C.