Microstructure and Mechanical Behavior of a New α+β- Type Mg-9Li-3Al-2.5Sr Alloy

摘要:

采用传统铸造方法分别制备了Φ10 mm和Φ90 mm Mg-9Li-3Al-2.5Sr (LAJ932)合金锭。在挤压温度260 ℃，挤压比28条件下对Φ90 mm合金锭进行挤压。分别分析和报道了铸态和挤压态LAJ932镁合金的微观组织和力学性能。探讨了该合金在挤压过程中的组织演变规律。研究结果表明：铸态和挤压态LAJ932镁合金均包括α-Mg (hcp)相，β-Li (bcc)相和Al4Sr相。Φ10 mm铸锭的组织比Φ90 mm铸锭组织细小得多。挤压过程中α-Mg相发生连续动态再结晶，而β-Li相发生非连续动态再结晶。挤压过程中，在hcp α-Mg相中形成{100}<100>织构，而bcc β-Li相中则形成{110}<101>织构。挤压过程中，LAJ932镁合金的强度和塑性均得到改善。挤压态Mg-9Li-3Al-2.5Sr(LAJ932)合金的抗拉强度达到235 MPa，屈服强度为221 MPa，延伸率为19.4%，合金展现出良好的力学性能。

Abstract:

The as-cast Mg-9Li-3Al-2.5Sr (LAJ932) alloy ingots with diameters of 10 mm and 90 mm were prepared. The extrusion of Φ90 mm as-cast LAJ932 alloy ingot was carried out at 533 K with an extrusion ratio of 28. The microstructure and the mechanical properties of the as-cast and extruded LAJ932 alloys were discussed. The microstructure evolution during extrusion was analyzed. The results show that both the as-cast and the extruded LAJ932 alloys contain hcp α-Mg, bcc β-Li and Al4Sr phase. The grain size of as-cast Φ10 mm specimen is smaller than that of Φ90 mm specimen. The microstructure evolution during extrusion is governed by continuous dynamic recrystallization (CDRX) in α-Mg phase whereas discontinuous dynamic recrystallization (DDRX) occurs in β-Li phase. {100}<100> texture is formed in the hcp α-Mg phase whereas {110}<101> texture is formed in the bcc β-Li phase during the extrusion process. Both the strength and the ductility of the LAJ932 alloy is improved by extrusion. The extruded LAJ932 alloy shows a favorable combination of the strength and the ductility with the tensile strength of 235 MPa, yield strength of 221 MPa and the elongation of 19.4%.