Simulation And Experimental Study On Rheo-Rolling Process Of A2017Alloy Under Action Of Shearing/Vibrating

In this paper, Based on the Natural Science Foundation of China (No.51034002), continuous rheo-rolling of A2017alloy under action of shearing/vibration was studied. Thermal and fluid multiple fields during manufacturing A2017alloy strip by continuous rheo-rolling process were simulated by FEM software. Effects of experimental parameters on microstructures were investigated and obtained, and the parameters have been optimized. Microstructures formation mechanisms of A2017alloy was investigated during the process of continuous rheo-rolling. Main work and results are described as follows:(1) The experimental device has been designed. The process conditions of continuous rheo-rolling of A2017alloy under action of shearing/vibrating have been set up.(2) Thermal and fluid multiple fields during continuous rheo-rolling of A2017alloy under action of shearing/vibrating were simulated by FEM software. Effects of process conditions on distributions of thermal and fluid multiple fields have been obtained. It could provide a reference for optimizing processing parameters.①On the sloping plate surface, alloy temperature decreases gradually from the casting mouth to the exit with a linear pattern, the alloy temperature near the sloping plate surface is lower than that on the above surface. The alloy velocity on the plate increases gradually from the casting mouth to the exit, the velocity near the plate is lower than that on the above surface. Both the temperatrue and velocity increase with the casting temperature.②In the roll gap, alloy temperature decreases gradually from the entrance to the exit of the roll gap, and the center alloy temperature is higher than that of the surface.The alloy temperature in the roll gap exit decreases with the casting temperature, but it has the little effect on the alloy velocity. Both the temperatrue and velocity increase with the roll speed.(3) The effects of process parameter of continuous rheo-rolling on microstructure of A2017alloy plate were obtained, and the experimental parameters have been optimized. When the casting temperature decrease from680℃to660℃, the solid fraction of the alloy increases, so the alloy was sheared enough. Roll speed varies from0.084m·s-1to0.105m·s-1, with the decrease of roll speed, the shear time increases and the grains grow in golobular form. The optimum processing condition is that the casting temperature is660℃～680℃, the roll speed is0.084m·s-1, the work roll is cooled by internal wate and the frequency of sloping plate is50Hz. Under this condition, the strip tensile strength is274MPa and elongation is12.7%.(4) Microstructures formation mechanisms of A2017alloy was analyzed during the process of continuous rheo-rolling under action of shearing/vibrating. The nucleation mechanisms on the sloping plate:①heterogeneous nucleation on the plate;②eruptive nucleation. The growing of crystal nucleus also had two ways:①direct globular growth;②dendrite arm necking and break to spheroidization. The semisolid slurry was made by the sloping plate will be cooled further in the roll gap. Under strong cooling provided by the water-cooling rolls, the primary grains grew further, and most of grains were elongated in the roll gap secondary crystallization was happened in the residual liquid.