中文摘要：

用近液相铸造方法制备了ZK60-2Ca半固态坯料。对其组织演变进行了研究，发现由于Zr的特殊细化作用，ZK60-2Ca合金直接获得球形或近球形的组织，无需经过枝晶球化过程。通过用不同冷却速率的铸模浇铸考察了冷却速率对铸造组织的影响，并对近液相铸造时静置时间对微观组织的影响进行了研究。结果表明，随浇铸温度的降低和静置时间延长至60min，晶粒逐渐细化并趋于均匀，晶粒尺寸达21gm，且圆度为1．29。随冷却速率的增加，晶粒细化并出现球化趋势。并对组织演变的机理进行了探讨。

英文摘要：

A semi-solid metal ingot of ZK60-2Ca alloy was prepared by near-liquidus casting, and its microstructure evolution was studied It is found that due to the special refining effect of Zr, ZK60-2Ca alloy directly achieves a spherical or nearly spherical structure, without the process of dendrite spheroidization. The effect of cooling rates on the casting microstructure was also investigated through adopting different moulds with various cooling rates. The effects of holding time on the microstructure of the alloy were also studied. The rgsults indicate that with the casting temperature decreasing and holding time extending to 60 min, the grains are refined and homogenized gradually, the grain size is 21 μm as well as the roundness is 1.29. With a bigger cooling rate, the grains become smaller and spherical. Irl addition, the evolution mechanism of casting microstructure for near-liquidus casting was discussed.