Study On Charging Behavior Of Semi - Solid ZCuSn10 Copper Alloy Simulated Casting

ZCuSn10 is casting copper alloy, it has been widely used in many fields due to its good elasticity, good fatigue resistance, good formability and weldability, high wear resistance and corrosion resistance. Semisolid metal forming technique is characterized by their smooth filling, small thermal shock of mould, products with high density, high mechanical properties, low forming force.However, because of the existence of liquid-solid two phase in the semisolid metal, its forming process can produce some behaviors including the rigid-plastic deformation, separation of liquid-solid two phase, which causes the defects including composition segregation, unhomogeneous microstructure and shrinkage. Therefore, the deformation behaviors of the semisolid metal must be study, which will reveal the viscoplastic deformation and flow mechanism of semisolid metal forming.The semi-solid ZCuSn10 billets were produced with strain induced melt activated(SIMA) method which includes hot rolling and reheating process. After reheating and holding process, the process of mold filling of castings was carried under different conditions, including rates, temperature and degree of filling.First of all, the influencing rules of filling conditions on the morphology and distribution of liquid and solid phases was analyzed. Results indicate that the solid skeleton of sample basically remains the same under the low filling degree, the liquid phase is still distributed between solid phase particles, there is less liquid phase distribution near the punch, the distribution is relatively more away from the punch. As the filling degree increased to a certain degree, separation appeared due to the different flow states of solid and liquid phase, Whether in 910℃ or 910℃. Filling rate has a great influence on microstructure evolution, the macro profile becomes coarser with the increase of filling rate, however, the collaborative of solid and liquid is better. According to the results of load-displacement curves of the filling process, the load increases with the increase of the displacement, higher filling temperature leads to the higher liquid fraction and low load in the filling process, higher filling rate leads to higher load under the same displacement.Secondly, by comparing the process of the as-cast copper alloy and semi-solid copper alloy under same filling conditions, results showed that the as-cast sample is difficult to deform because of its dendrite on early stage, the separation is obvious and load is high. The copper alloy with non-dendrite has lower load compared with the as-cast samples. However, both the dendrite and non-dendrite copper alloy have high load in the filling process because of the serious separation between solid and liquid phase, the adhesion of solid particles makes it difficult to deform.According to the observation of SEM and EDS of samples before and after the filling, results showed that element segregation appeared due to the separation of liquid phase, the observation of EBSD showed that deformation and recrystallization appeared.At the beginning of the filling process, the main deformation mechanism is sliding between solid particles (SS), along with a small amount of flow of liquid incorpotating solid particles (FLS) mechanism. The plastic deformation of solid particles (PDS) is main deformation mechanism in the later stage. Combining with law of micro structure evolution, the collaborative flow criteria of liquid-solid two phase of semisolid copper alloy is obtained. In a certain range, increasing temperature and filling rate will contribute to the improvement of the collaborative flow of solid and liquid phase of semi-solid copper alloy.