Study On Die Casting Processing And Performance Of Semi-solid ZL101 Alloy Prepared By Slope Tube Cooling Method

The rheo-diecasting technology of aluminum alloy can be well used in many fields. In this study, semi-solid slurry prepared by slope tube cooling method transfer to chamber rapidly for diecasting. The advantages of this technology include high efficiency, short process, simple equipment and easy to integrate with the traditional die-casting, etc.The semi-solid slurry of ZL101 aluminum alloy prepared by slope tube cooling method, slowly cooling in the crucible soon after, then quickly transferred to the chamber and casting. The process of semi-solid die casting was exploited on the basis of liquid die casting process. The results showed that the optimum parameters of liquid die casting in this case is that:pouring temperature is 630℃, mold preheating temperature is 100～140℃, injection pressure is 97MPa, injection punch speed is 0.8m/s, ingate speed is 8.8 m/s; for semi-solid die casting, slurry transfer temperature is 600℃, mold preheating temperature is 120～150℃, injection pressure is 97MPa, when injection punch speed is 0.8m/s and 1.18m/s respectively, corresponding ingate speed is 12.7m/s and 19.8m/s respectively, casting complete filling and the quality of apparent is good, when injection punch speed is 1.8m/s, the mechanical properties of casting is the best.The microstructure is observed by OM and SEM. It is show that the microstructure of both the low temperature pouring and semi-solid die casting are consists of large particles of primaryα-Al, fine particles of second primaryα2-Al and Al-Si eutectic structure. Compared with low temperature pouring die casting, the primaryα-Al particles in microstructure of semi-solid diecasting is greater, but more rounded; compared with the semi-solid billet, the size of eutectic Si phase is more smaller, the size of eutectic Si phase also is relate to the sampling location. the size of Si particles in runner is larger, Si particles in the internal cast is smaller, Si particles in the surface layer is the smallest. The microstructure uniformity of semi-solid die-casting is poor, mainly caused by low tempreature of chamber and mold.As the higher melt viscosity, during the rheocasting course, the semi-solid alloy slurries smoothly flow, and microstructures of samples are so dense and free of pores, therefore, semi-solid diecasting part out of Surface blister and deformation after heat treatment. After T6 heat treatment, the tensile strength increased by 8.5%, the elongation increased by 80%; Compared with liquid die casting, the tensile strength of semi-solid die casting parts slightly increased, but the elongation and hardness of the semi-solid sample as simile as the liquid die casting. The tensile fracture morphology is observed by SEM, it is show that both the low temperature pouring liquid die casting and semi-solid die casting samples were subject to cleavage fracture, while the heat treated specimen were ductile fracture.