薄壁铝合金压铸充型过程中的流动特征及其凝固组织

摘要

The viscosity of AlSi10MnMg aluminum alloy was measured by a rotational viscometer. The thin­wall fluidity samples were prepared by high pressure die casting. The filling velocity was recorded and analyzed by high speed camera system. Re and We were calculated to represent the flow characteristics during the filling process. OM was employed to study the microstructure. The results show that the rotational viscometer is suitable for the non­Newtonian fluid aluminum alloy melt system. The aluminum alloy melt fills the cavity of thin­wall fluidity specimen at a high­speed in the form of laminar flow when the melt free surface is broken into small droplets. While the viscosity decreases with the pouring temperature increasing, the filling fluidity time, velocity and length increase. High temperature increases porosity and causes that the morphology ofα(Al) grain changes from massive to spherical and rose­shaped. The grains become uniform with the temperature increasing. The porosity decreases firstly and then increases, but the change of grain size distribution is undetectable along fluidity length. Both the grain size andα(Al) phase in the center are higher than those in the boundary.%采用旋转黏度计测定AlSi10MnMg铝合金熔体的黏度，压铸制备薄壁铝合金铸件，并用高速摄像技术记录分析充型速度，计算流体力学参数Re数和We数来表征薄壁铝合金压铸充型过程中的流动特征，最后采用OM研究其组织。结果表明：旋转黏度计适合于测定非牛顿流体铝合金熔体系统；铝合金熔体以层流、充型前端液面自由表面破碎成细小液滴的形式高速填充薄壁流动试样型腔；浇注温度升高，黏度减小，充型时间、充型速度和充型距离增加，气孔增加，α(Al)晶粒由块状向球状、蔷薇状转变，晶粒尺寸分布越来越均匀；沿充型流动长度方向，气孔先增加后减少，晶粒尺寸分布变化不大；铸件中心位置晶粒尺寸、α(Al)相含量大于型壁边界位置。