Research On The Semi-Solid Thixoforging Process And Numerical Simulation Of Aluminum Alloy 2024

Semi-solid forming technology has got some advantages when comparing with some traditional processes, casting and forging, for instances. It can produce parts with non-dendritic grains and with complex shape. In this paper, thixoforming process of aluminum alloy 2024 was simulated, and a series of parts was produced by thixoforging. The microstructure and properties of products were studied along parameters such as pressure and the height of the billets. The pressure applied was changed in steps of 208MPa, 312MPa, 416MPa, and 624MPa. The height was changed to 48mm, 51mm, 56mm, and 62mm. The billets for thixoforging were prepares by the method SIMA. Microstructures of the products were observed by Optical Micrograph and Scanner Electron Microscope. Density and mechanical properties from different parts were tested as well.The temperature field and stress field of solidification process were simulated by numerical software ProCAST. It turned out that the solidification time varied in different part of the product, and the solidification time of the central area was shorter than the other area, while the solidification time was longer when the canvex platform was bigger. The solidification time increased as the height of the billet increased. When the applied pressure or the height of the billet increased, the temperature field and stress field tended to be more homogeneous, which would be useful to the decreasement of the defects.The microstructure showed that the structure and size of the grains from different positions varied, and the distribution of liquid phase and solid phase was not uniform. The grains of the central part deformed and were more dense than other parts, and the ununiformness of liquid phase and solid phase was more obvious as the canvex platform was bigger. When the applied pressure or the height of the billet increased, the distribution of liquid phase and solid phase from the central area and the surface was observed more uniform.The density and mechanical properties of different parts showed that properties of the central part were much better than other areas, and mechanical properties of the middle of the canvex plaform were better the the end. When the canvex platform was smaller, the microstructure tended to be denser and mechanical properties better. And properties improved as the height of the billet increased. Many speciemen taken from the canvex platform broke from where they were held, which indicated the poor mechanical properties of the end of the canvex platform.