不同预时效挤压态Mg−Gd−Y−Zn−Zr合金的再结晶行为和强化机制

Recrystallization behavior and strengthening mechanism of extruded Mg−Gd−Y−Zn−Zr alloy with different pre-aged states

通过控制预时效时间制备3种不同状态的试样,研究不同预时效状态对挤压态Mg−9.5Gd−4Y−2.2Zn−0.5Zr(质量分数,%)合金的动态再结晶行为(DRX)和性能的影响。结果表明,欠时效挤压(UAE)样品的细晶体积分数为17.4%,而峰时效挤压(PAE)和过时效挤压(OAE)样品的细晶体积分数分别达到89.7%和50.4%。在晶粒内部和晶界处分布的致密、细小的β颗粒相通过粒子激发形核机制显著提高了形核位点和位错密度。然而,致密针状γ'相抑制位错滑移,延迟DRX形核。PEA和OAE样品中细小晶粒的差异归因于原始颗粒相的数量和尺寸的不同,而其拉伸性能的差异归因于不同的显微组织。由于晶界强化和析出强化机制的贡献更大,PAE样品具有更优异的拉伸性能。

Three different samples were prepared by tailoring the pre-ageing time to investigate the effect of different pre-aged states on the dynamic recrystallization behavior and properties of extruded Mg−9.5Gd−4Y−2.2Zn−0.5Zr(wt.%)alloy.The results showed that the volume fraction of fine grains was 17.4%for under-aged extruded(UAE)sample,while that of the peak-aged extruded(PAE)and over-aged extruded(OAE)samples reached 89.7%and 50.4%,respectively.Dense and fineβparticles distributed inside grains and at grain boundaries significantly improved the nucleation sites and dislocation density through the particle-stimulated nucleation mechanism.However,the dense needle-likeγ'phase inhibited dislocation slip and delayed dynamic recrystallization(DRX)nucleation.The difference in the fine grains between the PEA and OAE samples was attributed to a difference in the quantity and size of the original particles,and the difference in their tensile properties was caused by different microstructural components.The higher contributions of grain boundary strengthening and precipitation strengthening mechanisms gave PAE sample better tensile properties.