中文摘要：

半固态金属坯料部分重熔是半固态金属触变成形工艺的重要技术环节，为了使坯料获得既细小又圆整的晶粒组织，对近液相线铸造ZK60镁合金半固态坯料进行部分重熔，通过改变重熔温度和保温时间来研究其微观组织的演化规律。结果表明：适当控制加热温度和保温时间，坯料部分重熔时可获良好的触变结构。石墨模浇注时，在600~605℃、保温10~15 min时可获得较理想的触变结构，平均晶粒尺寸达30.5μm，圆度达1.5；水冷铜模浇注时，可得出相同的结论，其晶粒平均直径为31.8μm，圆度达1.6。且坯料近液相线铸造时的冷却速率对部分重熔的进程也产生影响，适当降低铸造冷却速率，即采用石墨模能提高二次重熔组织的均匀性和稳定性。

英文摘要：

Partial remelting is the important part of semi-solid metal （SSM） ingots forming technology. In order to obtain small and round grain organization microstructure, the microstructure evolution of ZK60 magnesium alloy SSM ingots obtained by near-liquidus casting were partially remelted, and the microstructure evolution would be investigated by controlling remelting temperature and holding time. The results indicate that good thixotropic microstructure will be obtained by controlling remelting temperature and holding time suitably. Using the graphite mould, optimizing thixotropic microstructure can be obtained at 600-605℃for 10-15 min, the average diameter of grain is 30.5μm and the roundness is 1.5. With the water-cooled copper mould, the conclusion is the same, the average grain diameter is 31.8μm and the roundness is 1.6. Meanwhile, the cooling rates during casting also affect the partial remelting progress, reducing the cooling rate properly, the graphite mould can improve the uniformity and stability of the partial remelting microstructure.