采用轧制-重熔的SIMA法制备了ZCuSn10合金半固态坯料, 先将铸态ZCuSn10合金加热到450 ℃保温15 min, 分别进行2~4道次轧制, 然后截取试样进行重熔处理后水淬. 比较了SIMA法和铸态-直接重熔工艺制备的ZCuSn10合金半固态组织, 并利用SEM的EDS测定了组织中Sn的分布情况, 用OM和TEM观察了SIMA法制备过程中试样组织变化, 综合分析了SIMA法制备ZCuSn10合金半固态坯料过程中的组织演变机理. 结果表明: 采用轧制-重熔的SIMA法制备的ZCuSn10合金半固态组织固相晶粒均匀细小, 圆整度高, 19.7%预变形量875 ℃保温15 min半固态组织最优, 其平均晶粒直径75.8 μm, 形状因子1.62, 液相率17.28%; 用SIMA法制备ZCuSn10合金半固态坯料, 预变形过程对晶粒细化及球化起到了关键作用, 随着预变形量和重熔保温温度的提高, 半固态组织晶粒尺寸减小, 圆整度提高, 液相率增加; 采用轧制-重熔的SIMA法制备ZCuSn10合金半固态组织球化的主要机理是预变形过程破碎了枝晶, 储备了变形能, 在重熔过程中促进了枝晶熔断, 同时, 由于Sn元素从液相中向α固相中扩散迁移, 液相逐渐吞噬固相的尖角突出部分, 最终生成细小、圆整的α相晶粒.

Semi-solid billet of ZCuSn10 alloy is prepared by strain induced melt activation (SIMA) method which included the rolling and remelting process. Firstly, ZCuSn10 alloy is cast, and samples are cut from ingot casting. Secondly, the samples are rolled with 2~4 passes after holding at 450 ℃ for 15 min, then the new samples are cut from deformed alloy. Lastly, the new samples are reheated up to 850 ℃ or 875 ℃ for 15 min, then water quenching. Semi-solid microstructure is observed and compared with microstructure of ZCuSn10 alloy directly reheated after casting. The distribution of Sn element in microstructure under different conditions is measured by using EDS function of SEM, and the microstructure changes during the SIMA process are observed by means of OM and TEM. Based on the experiments, the microstructure evolution is synthetically analyzed and explained during the course of semi-solid billet of ZCuSn10 alloy prepared by SIMA method. The results indicate that semi-solid microstructure of ZCuSn10 alloy by rolling- remelting SIMA process is equal-fine grain, and spheroidization of solid particle is well. The optimum semi-solid microstructure is obtained when alloy deformed 19.7% is remelted at 875 ℃ for 15 min, the average grain diameter is 75.8 μm, shape factor is 1.62, and volume fraction of liquid phase is 17.28%. Deformation process plays a crucial role in grain refinement and spheroidization during SIMA process for preparing the semi-solid billet of ZCuSn10 alloy, as deformation and remelting temperature increases, the size and shape of solid phase in semi solid microstructure are smaller and more round, volume fraction of liquid phase increases. The main mechanism of SIMA process preparing semi-solid billet of ZCuSn10 alloy is that predeformation breaks dendrites and stores energy of deformation into dendrites, and promotes dendrites melting through remelting process. Meanwhile, liquid phase occupies sharp corners of solid particles by Sn element diffusing from liquid phase into α solid phase, so that fine, uniform and roundness α solid particles are gained.