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利用稀土元素Pr对过共晶Mg-4Si合金中的初生Mg2Si相进行变质处理,并讨论其变质机理.结果表明:Pr对Mg-4Si中的初生Mg2Si相可以起到有效的变质作用,在Pr质量分数为3%时,变质效果最佳;随着Pr的加入,初生Mg2Si相形态上从花瓣状的树枝晶转变为颗粒状的多边形,尺寸由200μm降到60μm;随着Pr的加入,有白亮的纤维状新相生成,经EDS分析该相为Pr2Si3相;Pr通过表面溶质富集抑制初生Mg2Si相择优生长,Pr2Si3相起到异质形核作用,从而对初生Mg2Si相变质.
The primary Mg2Si phase in the hypereutectic Mg-4Si alloy was treated by rare earth element Pr and its metamorphic mechanism was discussed.The results show that Pr can effectively modify the primary Mg2Si phase in Mg-4Si, With the mass fraction of 3%, the metamorphic effect is the best. With the addition of Pr, the morphology of the primary Mg2Si phase changes from petal-shaped dendrites to granular polygons, the size decreases from 200μm to 60μm. With the addition of Pr, White bright fibrous new phase, EDS analysis of the phase Pr2Si3 phase; Pr surface solute enrichment inhibition of primary Mg2Si preferred growth, Pr2Si3 phase heterogeneous nucleation, resulting in primary Mg2Si phase transition.