Study On Thermal Fatigue Relief Mechanism Of Aluminum Alloy Die-casting Die Based On ProCAST

During the aluminum alloy die casting process,die surface is rapidly heated and cooled periodically,which is prone to generate thermal fatigue failure,and then shorten in-service tool life.The experimental method is costly and long time consuming;and it is hard to build ideal model in theoretical calculation,thus using numerical method to study the thermal fatigue relief mechanism has significant meaning on improving thermal fatigue life of aluminum alloy die-casting die.The 2D model of the field joint was built using ProC AST software,the temperature field,effective stress field,effective plastic strain field and the method of evaluating the thermal fatigue life of aluminum ally die-casting die were analyzed,and orthogonal test was used to optimize the process parameters.The 2D layered die-casting die model of the field joint was built using ProCAST software,the materials and preparation process were chosen.The temperature field,effective stress field,effective plastic strain field of the layered die-casting die were analyzed,the thermal fatigue life of the three kind of layered was calculated and the effect of the materials of the cladding on the thermal fatigue life of the layered die-casting die was compared.The conclusions of this paper are as follows:?1?For homogeneous die-casting die,during the thermal equilibrium formation process,the temperatures of the nodes increase and the growth rates decrease gradually,the effective stresses of the nodes increase at first and then decrease gradually.In the heat balance state,the closer to the cavity surface,the higher the temperature and effective stress fluctuation.The effective plastic strain is mainly accumulated during the thermal equilibrium formation process.?2?The processing parameters were optimized through orthogonal experiment based on the formula of thermal fatigue life and the optimum processing parameters are the pouring temperature of 600?,the die preheating temperature of 250?,the heat transfer coefficient of release agent of 400 W/?m²·k?.?3?Compared with homogeneous die-casting die,during the thermal equilibrium formation process,the effective stresses of the nodes increase and the growth rates of the nodes in the cladding decrease gradually,and the effective plastic strains of the nodes decrease significantly.In the heat balance state,the temperature fluctuation ranges of the nodes of the layered die-casting die decrease compared with the homogeneous die-casting die.The fluctuation ranges of the temperatures and effective stresses of the nodes and the effective plastic strains increase when ceramic materials are added into the N i60 cladding.?4?The thermal fatigue is more likely to appear on the surface of the cavity.The thermal fatigue life of die-casting die with coating material N i60,N i60+TiC and Ni60+Al₂O₃ are 840000,1200000 and 1600000 cycles,respectively.Compared with the thermal fatigue life of the homo geneous die-casting die,the service life of the layered die-casting dies are much longer,thus the cladding coating can improve the thermal fatigue life effectively,and Al₂O₃ was better than TiC at improving the thermal fatigue life of the die-casting die.