转动输送管制浆工艺参数对A356合金半固态组织的影响

利用开发的低转速输送管控制浇注工艺制备了A356合金半固态组织,从不同浇注温度、不同转动速度下晶核的来源和不同结晶器冷却强度下游离晶演变的2个角度,结合凝固微观组织模拟技术分析了非枝晶组织的形成与演变规律.结果表明:适当的低温浇注和输送管转速可极大地提高有效形核数目,降低熔体的冷却强度有利于初生相呈球形生长;晶粒周围溶质扩散层的叠加影响着液/固界面处引起界面失稳的浓度梯度,进而影响初生相的生长形态.

Effects of parameters of slurry-making process with rotating duct on semi-solid microstructure of A356 alloy

Semi-solid slurry of A356 alloy was produced by a controlled pouring process with a rotating duct. Nucleation behavior and morphology evolution of primary phase under different pouring temperatures were investigated. Rotating speeds of the duct and cooling intensity of crucible were studied. The formation of non-dendrite was analyzed through experiments and microstructure simulation technique. The results show that appropriate combination between pouring temperature and rotating speed of duct can significantly improve effective nucleation rate, decreasing the cooling intensity of the melt metal can give rise to a transition of the growth morphology from dendritic to rosette and to spheroid. Results from simulations indicate that the overlapping diffusion fields from adjacent growing crystals can influence the morphology of crystal by influencing the concentration gradients that can cause instabilities at solid/liquid interface.