Investigation On Technique Of Rheo Die-casting For Semi-Solid A380 Aluminum Alloy

Traditional die-casting internal defect ratios are always high, and can not easily do the heat treatment, so how to reduce these defect ratios is an emergent question which needs to be solved has already gathered much concern of scholars.In order to improve the mechanical properties for Jiang ling die-casting corporation, the paper systematically does some research on semi-solid rheological forming technology mainly on testing bar which is made of A380 aluminum casting alloy.And the study uses a novel rheocasting process ,termed as Low Superheat Pouring with a Shear Field(LSPSF) to prepare semi-solid slurry, the forming equipment is die-casting machine(DCC280). The paper include three parts:the optimization of the LSPSF technical parameters. the microstructure and mechanical properties of liquid die-casting parts and semi-solid die-casting parts before and after heat treatment, then does analysis and research on the influence of rheological die-casting technical parameters to the performance of castings. Research method and main results is as following:(1) we received the best microstructure of the A3 80 semisolid aluminum slurry when the rotating speed is 90rev/min , pouring temperature is 620℃, inclined degree is 25°and the temperature of the crucible is 550℃. Pouring temperature and rotation speed of barrel determine the stirring-mixing intensity and cooling ability applied by the rotational barrel on the molten alloy. It can be concluded that sound semi-solid metal slurry can be produced under the appreciate combination of pouring temperature and rotation speed of barrel.(2) Under LSPSF process, low superheat pouring combined with localized rapid cooling and vigorous mixing during the initial stage of solidification can enhance wall nucleation, crystal separation and crystal survival. Moreover the effective nucleation rate is significantly affected by the combined effects of pouring temperature and rotation speed of barrel.(3) Mechanical property test shows that semi-solid die-casting and liquid die-casting have almost the same tensile strength before they are heat treatmented. but the ductility of the semi-solid forming parts is almost two times than that of liquid forming parts. After T6 heat treatment, the tensile strength improved and the ductility inclined for both semi-solid die-casting and liquid die-casting , but they have different variation range.(4) The result shows that these parameters should be strictly controlled or the mechanical properties will fall down because of the defects producing, though under semi-solid rheological die-casting. However, the results of semi-solid one is better than the traditional one, accompanied with descending of pouring point and reducing of detects, finally gains more near-circular and smaller structures.the mechnical properties more improved.