中文摘要：

在等温稳态条件下，对半固态AZ91合金浆料的晶粒密度进行了研究：在相同的剪切速率下搅拌，温度越低，固态镁合金晶粒密度越大；在相同温度条件下搅拌，随着剪切速率的增加，晶粒密度逐渐增加，当增加到一定值时，晶粒密度达到最大值，随后随着剪切速率的增加，晶粒密度减小，即随着剪切速率的变化，存在一个最佳剪切速率，使得晶粒密度最大。分析了搅拌时间对晶粒密度的影响，说明半固态浆料的搅拌时间不宜过长。同时还进行了在金属型中成形与水淬的半固态镁合金试样晶粒密度的比较，并得到了相似的规律。该结果为半固态AZ91合金压铸过程的数值模拟及进一步的试验研究提供了有用的数据。

英文摘要：

The grain density of semi-solid AZ91 magnesium alloy in the condition of isothermal and steady state was studied. For the same shear rate, grain density of magnesium was higher with lower stirring temperature. Under the same stirring temperature,＂ grain density increased gradually with the increasing of shear rate. Grain density arrived at the max with the increasing of rate of shear and then reduced. With the change of rate of shear, an optimal value for shear ratewas appeared in that time grain density arrived at the max. Then the relationship of grain density and stirring was studied. It showed that the stirring time for semi-solid slurry should not too long. It get the same rules from the experiment of shaping in the metal mould and water quenching one. The results provided useful data to the numerical simulation and next experiment of semi-solid AZ91 alloy.