论文部分内容阅读
In the present research, semisolid billet of 7005 aluminum alloy was fabricated by using recrystallization and partial remelting(RAP), then thixoformed at different isothermal temperatures, preheating temperatures and load routes. Mechanical properties and microstructure of the thixoformed product were investigated. The results showed that microstructure achieved by three-step induction heating warm extruded 7005 aluminum alloy consists of a uniform and spheroidal microstructure suitable for thixoforming.Preheating temperature of the die affected signi?cantly the ?lling status of semisolid billet of 7005 aluminum alloy. Complete ?lling status with good surface quality was obtained at a preheating temperature of 365 °C. Thixoformed microstructures consisting of relatively spheroidal grains illustrate the dependence of ?lling process on the sliding and rotating of solid grains rather than plastic deformation of solid grains. A non-uniform distribution of liquid phase was found in the different regions of the thixoformed product due to the slower adjustable velocity of solid grains as compared with liquid phase. Increase of isothermal temperatures led to a slight decrease of mechanical properties of the thixoformed product due to coarsening of solid grains. The highest yield strength, ultimate tensile strength and elongation of thixoformed components with T6 heat treatment are 237 MPa, 361 MPa and 16.8%, respectively, which were achieved at the isothermal temperature of 605 °C. Load route has a signi?cant effect on mechanical properties and microstructure of the thixoformed product. Defects, such as crack and microporosity occurred in the microstructure of the thixoformed product obtained under load route 2. It led to an obvious reduction of mechanical properties as compared with route 1. A better compatibility of deformation caused by more liquid fraction at the isothermal temperature of 612 °C is bene?cial to reducing nonuniformity of liquid phase in the different regions of the thixoformed product.
In the present research, semisolid billet of 7005 aluminum alloy was fabricated by using recrystallization and partial remelting (RAP), then thixoformed at different isothermal temperatures, preheating temperatures and load routes. The properties showed that the thixoformed product were investigated. that microstructure achieved by three-step induction heating warm extruded 7005 aluminum alloy consists of a uniform and spheroidal microstructure suitable for thixoforming. Plyating temperature of the die affected signi? cantly the lling status of semisolid billet of 7005 aluminum alloy. Complete? lling status with good surface quality was obtained at a preheating temperature of 365 ° C. Thixoformed microstructures consisting of relatively spheroidal grains illustrate the dependence of? lling process on the sliding and rotating of solid grains rather than plastic deformation of solid grains. A non-uniform distribution of liquid phase was found in the di fferent regions of the thixoformed product due to the slower adjustable velocity of solid grains as compared with liquid phase. Increase of isothermal temperatures led led to a slight decrease of mechanical properties of the thixoformed product due to coarsening of solid grains. tensile strength and elongation of thixoformed components with T6 heat treatment are 237 MPa, 361 MPa and 16.8% respectively, which were achieved at the isothermal temperature of 605 ° C. Load route has a signi? cant effect on mechanical properties and microstructure of the thixoformed product. Defects, such as crack and microporosity in the microstructure of the thixoformed product obtained under load route 2. It led to an obvious reduction of mechanical properties as compared with route 1. A better compatibility of deformation caused by more liquid fraction at the isothermal temperature of 612 ° C is bene? cial to reducing nonuniformity of liquid phase in the different regions of the thixoformed product.