流变铸造AZ91-Sn合金的组织演化、拉伸行为及磨损性能

Microstructure Evolution, Tensile Behavior, and Wear Properties of AZ91 Alloys with Different Sn Contents by Rheocasting

摘要:

研究了不同Sn含量流变铸造AZ91合金的组织演化、拉伸行为及磨损性能。结果表明：Sn的合金化改变了Al在镁基体中的固溶度，并且显著细化了微观组织。加入0.8%（质量分数，下同）的Sn后，合金平均晶粒尺寸从105.0 μm降至42.1 μm。高熔点的金属间化合物为析出相提供了异质形核点，这些弥散析出的第二相在流变凝固过程中有效地细化了镁基体。弥散分布的第二相抑制了枝晶组织生长，从而进一步提升了合金的力学性能。随着Sn含量的增加，合金磨损率显著降低，磨粒磨损逐渐消失。3.0%Sn合金化的流变铸造AZ91合金具有最高的抗拉伸强度以及最好的耐磨损性能。

Abstract:

The effect of different Sn contents on microstructure evolution, tensile behavior, and wear properties of AZ91 alloys by rheocasting was studied. The results show that the presence of Sn changes the solid solubility of Al in Mg matrix and effectively refines the microstructure of alloy matrix. The average grain size is refined from 105.0 μm to 42.1 μm after addition of 0.8wt% Sn. The heterogeneous precipitate nuclei are formed by the intermetallics with high melting point, which effectively refines the magnesium matrix during the rheo-solidification. These dispersed second phases suppress the formation of dendrites, further improving the mechanical properties. With increasing the Sn content, the wear rate of alloys is obviously decreased and the abrasive wear disappears gradually. The rheocast AZ91 alloy with addition of 3.0wt% Sn has the highest tensile strength and the best wear resistance.