含不同初始织构的Mg−Gd−Y−Zn−Zr合金热轧板材的显微组织和力学性能

Microstructure and mechanical properties of Mg−Gd−Y−Zn−Zr alloy plates with different initial textures after hot rolling

通过光学显微镜、扫描电子显微镜、电子背散射衍射、透射电子显微镜和拉伸试验研究含不同初始织构的Mg−4.7Gd−3.4Y−1.2Zn−0.5Zr(质量分数,%)合金热轧板材的显微组织和力学性能。结果表明,初始织构为0001//RD(板材轧向)的板材获得相对较粗的晶粒和双峰基面织构;而初始织构为0001//TD(板材横向)的板材动态再结晶程度更高,因此,获得更细的晶粒尺寸和较强的0001//ND基面织构。此外,在两种板材中均发现沿RD拉长的不规则形状LPSO相,这种LPSO相导致各向异性的承载强化行为,并进一步引起板材的屈服各向异性。对强化机理的分析表明,晶界强化对轧制板材的强化效果最好。由于具有较小的晶粒尺寸和LPSO相带来的承载强化效果,初始织构为0001//TD的板材在RD方向上获得最高的屈服强度。

The effects of initial textures on the microstructures and mechanical properties of rolled Mg−4.7Gd−3.4Y−1.2Zn−0.5Zr(wt.%)plates were studied by optical microscope(OM),scanning electron microscope(SEM),electron backscatter diffraction(EBSD),transmission electron microscope(TEM)and tensile test.In the plate with an initial texture of 0001//RD(rolling direction),relatively coarse grains and bimodal basal texture are developed.However,in the plate with an initial texture of 0001//TD(transverse direction),finer grain size and strong 0001//ND basal textures are obtained due to the higher degree of dynamic recrystallization during rolling.Additionally,the irregular-shaped long-period stacking ordered(LPSO)phases are elongated along RD in both plates,which results in anisotropic load-bearing strengthening behavior,and further leads to a certain degree of yield anisotropy.The analysis of the strengthening mechanism shows that grain boundary strengthening is the most effective strengthening method in the plates.Because of the finer grain size and the strengthening caused by the elongated irregular-shaped LPSO phases,the rolled plate with an initial 0001//TD texture achieves the highest yield strength along RD.