Rheological Behavior of Semi-Solid AZ91D Magnesium Alloy at Steady State

The rheological behavior of semi-solid AZ91D magnesium alloy was investigated in isothermal steady state condition. The effects of stirring temperature and shearing rate on apparent viscosity of semi-solid alloy slurry at steady state were discussed. The results show that the apparent viscosity of semisolid AZ91D alloy increases with increasing solid fraction. It increases slightly before the solid fraction reaches a certain value, about 0.4, and then goes up rapidly aider the solid fraction reaches the critical value. However, the apparent viscosity decreases with increasing shearing rate, and the reduction amplitude is higher when the solid fraction is higher. According to the experimental data, an empirical equation that shows the effect of solid fraction and sheafing rate on the apparent viscosity of semi-solid AZ91D alloy can be built as ηa=9.7×10^-2 exp（13.87fs）γ^-0.58.

半固态金属流变仪的研制

根据同轴圆筒旋转法粘度测量原理自行研制了1台半固态金属流变仪,并通过测量甘油的粘度来检验流变仪的测量精度。在3个不同温度下测得的甘油绝对粘度值与标准值接近。用该台流变仪研究半固态A356铝合金的流变特性表明:半固态浆料稳态表观粘度随着剪切速率的增大而下降,且浆料温度越低,伪塑性越明显;当固相率小于10%时,在高剪切速率下浆料呈现出牛顿流体的特征;在连续冷却条件下,半固态浆料的表观粘度随着温度的降低而先缓慢后迅速增大,冷却速度显著影响半固态合金的表观粘度。