含长周期堆垛有序结构Mg94Zn2Y4挤压态合金的显微组织与力学性能

采用SEM和TEM等分析方法研究包含长周期堆垛有序结构的挤压态Mg94Zn2Y4合金的显微组织和力学性能。结果表明：铸态Mg94Zn2Y4合金由18R-LPSO和α-Mg两相组成。挤压后，长周期相分层，并形成宽度为50~200 nm的α-Mg 薄片。合金经498 K时效处理36 h后达到时效峰值，在其组织中析出β′相，该析出相的出现显著提高了α-Mg基体的显微硬度，从HV108.9增加到HV129.7；而LPSO结构的显微硬度稳定在HV145左右。TEM分析及其电子衍射花样表明，β′相与α-Mg和LPSO结构具有独特的位相关系，其原子最密排面的堆垛方向垂直于α-Mg和LPSO相最密排面的堆垛方向。由于β′相和18R-LPSO相的共同存在，处于时效峰值态的Mg94Zn2Y4合金的抗拉强度达到410.7 MPa。

Microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy with long-period stacking ordered structure

The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.