自孕育法流变压铸AZ91D镁合金微观组织特征

Microstructural Characteristics of Rheo-Diecasting AZ91D Magnesium Alloy Produced by Self-Inoculation Method

采用一种新的自孕育法制备AZ91D镁合金半固态浆料，研究了AZ91D镁合金半固态浆料的流变压铸成形，并对半固态浆料和压铸件的微观组织进行研究分析。结果表明，自孕育法可以制备出组织细小、均匀的半固态浆料。将自孕育法制备半固态浆料短时保温后，浆料中初生Ⅱ（Mg）内部没有液相夹裹，平均晶粒尺寸为70．4μm；在增压压力为180MPa，压射充型速度在2～5m／s内，经585℃保温10min的AZ91D镁合金半固态浆料能顺利进行流变压铸，能够改善AZ91D镁合金铸件的微观组织，获得性能良好的半固态压铸件。

By using of the novel self-inoculation preparation method of the semi-solid slurry of AZ91D alloy, the rheo-diecasting process of AZ91D semi-solid slurry was investigated and the microstructure of the semi-solid slurry and die castings was analyzed. The results indicate that semi-solid slurry with much finer and uniformer primary phases is gained by the method, and the average diameter of the grains is 70.4 μm. No entrapped liquid is found in the primary a（Mg） phase after the semi-solid slurry is held for a short time at the temperature of semi-solid range. The rheo-diecasting semi-solid castings with improved microstructure and good properties can be obtained when the pressurization reached 180 MPa, the injection speed is in 2-5 m/s and holding at 585 ℃ for 10 min.