目的 针对高强镁合金成形性差的难题,通过调控挤压速率以优化Mg-Gd-Y-Zn-Zr合金的微观组织与力学性能,为高塑性镁合金的热加工提供新的理论依据。方法 以Mg-9.5Gd-3Y-2Zn-0.3Zr合金为研究对象,在挤压速率分别为0.1 mm/s和1 mm/s条件下进行热挤压实验。通过金相显微镜、扫描电子显微镜、背散射电子衍射技术和透射电子显微技术等手段系统表征显微组织演变、第二相分布、动态再结晶行为及织构特征,并通过室温拉伸实验分析力学性能变化规律。结果 挤压后,显微组织由拉长的变形晶粒与动态再结晶晶粒组成。第二相沿晶界呈拉长形态分布,晶粒内部则动态析出片层状LPSO相,且其弯曲变形程度随挤压速率的提高显著加剧。随挤压速率的提高,动态再结晶体积分数增加,导致合金强度显著下降,延伸率仅小幅提升。结论 提高挤压速率虽在一定程度上提高了塑性,但会导致强度明显降低,反而不利于合金综合力学性能。挤压速率通过影响动态再结晶程度与织构特征,显著调控了合金的强塑性匹配。因此,合理选择挤压速率,是优化该镁合金强塑性平衡的关键工艺路径。
Abstract
Aiming at the challenge of poor formability in high-strength magnesium alloys, the work aims to optimize the microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloys by modulating the extrusion rate, so as to provide a new theoretical basis for the thermomechanical processing of high-ductility magnesium alloys. Hot extrusion experiments were conducted at 480 ℃ and 0.1 mm/s and 1 mm/s. The microstructural evolution, second-phase distribution, dynamic recrystallization behavior, and texture characteristics of the extruded samples were examined by optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Room-temperature tensile tests were performed to evaluate the mechanical properties. After extrusion, the microstructure consisted of elongated deformed grains and dynamically recrystallized grains. The second phases were distributed in an elongated morphology along grain boundaries, while lamellar LPSO phases were dynamically precipitated within the grains. The degree of their bending deformation significantly increased with the increase of extrusion rate. With the increase of extrusion rate, the volume fraction of dynamic recrystallization increased, leading to a significant decrease in alloy strength, while the elongation was only improved slightly. In conclusion, although increasing the extrusion rate can improve plasticity to a certain extent, it will cause a significant reduction in strength, which is not conducive to the comprehensive mechanical properties of the alloy. The strength and plasticity matching of the alloy is regulated by the extrusion rate which influences the degree of dynamic recrystallization and texture characteristics. Therefore, it is a key technological path to reasonably choose an appropriate extrusion rate for optimizing the strength-plasticity balance of magnesium alloys.
关键词
Mg-Gd-Y-Zn-Zr合金 /
LPSO相 /
挤压速率 /
动态再结晶 /
力学性能
Key words
Mg-Gd-Y-Zn-Zr alloys /
LPSO phase /
extrusion rate /
dynamic recrystallization /
mechanical property
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