AZ91D镁合金近液相线铸造研究

采用近液相铸造的方法浇铸了镁合金AZ91D，并与液相铸造的组织进行了对比，通过不同铸模浇铸考察了冷却速率对组织的影响，研究了近液相线铸造时的静置时间对铸造组织的影响，实验结果表明，液相（600℃）铸造组织与常规铸造组织接近，高冷却速率促进了枝晶化，近液相线铸造方法有利于组织的细化和球化，但不如铝合金显著，增加冷却加速率有利于组织的细化，也促进了球化的趋势，并对近液相线组织的演变机理进行了初步探讨。

STUDY ON THE NEAR-LIQUIDUS CASTING OF AZ91D MAGNESIUM ALLOY

The near-liquidus casting process was used in casting AZ91D alloy, and its microstruc- ture was compared with that prepared by liquid casting. The effects of cooling rate in casting process and the holding time in near-liquidus on rnicrostructure were also observed. The results indicate that the microstructure obtained from liquid casting is similar to that of conventional casting, and den- driticization is promoted at higher cooling rate. On the contrary, near liquidus casting is beneficial to refining and spheriodization of casting microstructure, however, whose effect is not apparent as comparing with aluminum alloy. The refining degree increases with increasing cooling rate, and the evolution mechanism of casting microstructure for near-liquidus casting was discussed.