Study On Liquid Extrusion For ZA43 Alloy

The liquid extrusion process is a new forming technology which is developed on the basis of the squeeze casting and the hot extrusion. It not only retains the character of liquid metal crystallized under pressure, but also imparts to the alloy significant plastic deformation. The notable level of the effect of the processing parameters in liquid extrusion on the mechanical properties of ZA43 alloy was studied with the help of the orthogonal experiments. A reasonable extent of parameters was determined. The forming reasons and influencing factors to the structure in different sections were analyzed through observing macrostructure.and microstructure of ZA43 alloy by liquid extrusion process. The forming features of the process were discussed and the measures of improving and reducing transition structure were raised. The expressions of unit pressure and half cone angle were established by applying upper limit principle. The value of critical specific pressure was determined. The flow velocity and equivalent strain of the metal in the process of liquid extrusion were analyzed. Furthermore, the effect of alloying and heat treatment on the microstructure and mechanical properties of ZA43 alloy were studied.The experimental results show that the order of influential factor is deferring period before applying pressure, pouring temperature and die temperature. The influence of the deferring period before applying pressure on mechanical properties of ZA43 Alloy is the most remarkable. The befitting processing parameters obtained in the experiment are that the mold temperature is about 160 , the pouring temperature is 630-670 and the deferring period before applying pressure is 15-22s. The mechanical properties of ZA43 alloy are highly improved. Especially, the elongation of the alloy is greatly improved. The characteristics of macro structure of ZA43 alloy are distinct. The marked streamlines in side wall of workpiece are50405caused by the difference of solid phase ratio. The microstructure of ZA43 alloy is tiny and uniform. The characteristics of deformation of the alloy are remarkable. A transitionary section exist in the side wall of the liquid extrusion workpiece by observing macrostructure and microstructure of ZA43 alloy. The influencing factor on the value of critical specific pressure include ratio of section reduced, height to thickness ratio, friction factor, half cone angle and the high temperature yield limit of metal. The flow velocity of metal reduces gradually from center to side along radius in deformation region. The equivalent strain of metal increases from center to side along radius in deformation region. The shorter the distance away from the exit of' the cavity of mould, the greater the flow velocity and equivalent strain of the metal along axes in deformation region. The difference of solid phase ratio is an important influencing factor on flow and deformation of the metal. The element Mg joined to the alloy make plasticity increase markedly. Strengthening function of Cu and Mn is quite bright. Choosing heat treatment process reasonably is a effective method to obtain the workpiece required.