双螺杆机械搅拌半固态镁合金的组织与性能

Microstructure and mechanical property of semi-solid magnesium alloy fabricated by twin-screw stirring

采用双螺杆机械搅拌制浆机和半固态流变压铸成形工艺制备AZ91D镁合金半固态浆料,研究了材料性能与微观组织之间的关系．结果表明,随着镁液的浇注温度或搅拌机简体温度的降低,半固态浆料的固相率越高,初生α～Mg相晶粒变得更细小和圆整,简体温度比镁液浇注温度的影响更显著．当浆料固相率控制在30%～45%时,半固态流变压铸成形镁合金铸件具有较高的抗拉强度和延伸率；随着晶粒平均尺寸的增加,材料的力学性能逐渐降低．提出了高剪切速率下流变压铸成形非枝晶组织的形成机理．

The semi-solid slurry of AZ91D magnesium alloy was prepared by twin-screw stirring mixer, and the relationship between mechanical properties and microstructure for semi-solid magnesium alloy were investigated. The results showed that the solid fraction of primary α-Mg phase increased and the grains became finer and rounder with reducing pouring temperature of the Mg melt or the barrel temperature of stirring machine. Furthermore, the effect of the pouring temperature of Mg melt on the solid fraction in slurry was bigger than that of the barrel preheating temperature. The tensile strength and elongation of rheo-diecasting AZ91D alloy were best when the solid fraction controlled in the range 30% to 45%, and the mechanical properties were deteriorated gradually with the increase of the average size of primary α phase grains. The formation mechanism of non-dentritic structure under the condition of high shear rate and rheo-cliecasting process was proposed.