目的 探讨了电脉冲处理对轧制态AZ31镁合金显微组织演变及力学性能的影响机制。方法 通过调控电流密度和频率,结合金相观察、XRD分析、力学性能测试及断口形貌表征,揭示了电脉冲处理诱导动态再结晶与β-Mg17Al12相低温溶解的协同作用机理。结果 脉冲电流的焦耳热效应和电子风力协同促进了晶粒的等轴细化,当电流密度为37.5 A/mm2、频率为200 Hz时,晶粒尺寸由轧态的24.59 μm细化至18.65 μm,延伸率提升了133%,抗拉强度仅下降了7.2%。XRD分析结果表明,β相在250 ℃以下发生非热溶解。究其原因是电子风力驱动Al原子扩散;同时,脉冲电流诱导位错增殖形成的界面缺陷提供了更多的原子扩散通道,加速了β相的溶解。断口形貌从脆韧混合型向全韧性转变,韧窝密度与尺寸随再结晶程度的增加而显著优化。显微硬度测试结果显示,随着电流密度和频率的增大,硬度逐渐下降,该变化趋势与镁合金的再结晶程度和位错密度降低相关。结论 电脉冲处理通过细化组织、溶解脆性相及降低位错密度,使AZ31镁合金的强塑性匹配性得到有效改善,为镁合金短流程精密成形技术提供了理论支持与工艺优化方向。
Abstract
The work aims to systematically investigate the effect of electropulsing treatment (EPT) on the microstructural evolution and mechanical properties of rolled AZ31 magnesium alloy. By regulating current density and frequency, combined with metallographic observation, XRD analysis, mechanical testing, and fractography characterization, the synergistic mechanisms of EPT-induced dynamic recrystallization and low-temperature dissolution of the β-Mg17Al12 phase were revealed. The combined effects of Joule heating and electron wind force significantly promoted equiaxed grain refinement. Under optimized parameters (37.5 A/mm2, 200 Hz), the grain size was refined from 24.59 μm (as-rolled) to 18.65 μm, accompanied by a 133% increase in elongation and a marginal 7.2% reduction in tensile strength. XRD analysis revealed that the β phase underwent athermal dissolution below 250 ℃. This phenomenon was attributed to the electron wind force driving the diffusion of Al atoms, while the pulsed current-induced dislocation multiplication generated interfacial defects, providing additional diffusion pathways for atoms and thereby promoting the dissolution of the β phase. Fracture morphology transitioned from a mixed brittle-ductile mode to a fully ductile mode, with dimple density and size exhibiting significant optimization as recrystallization progressed. Microhardness testing indicated a gradual decline in hardness with the increasing current density and frequency, which was consistent with reduced dislocation density and enhanced recrystallization. EPT effectively improves the strength-ductility balance of AZ31 alloy through grain refinement, dissolution of brittle phases, and dislocation elimination, offering critical theoretical insights and technical guidance for advancing short-process precision forming technologies in magnesium alloy applications.
关键词
AZ31镁合金 /
电脉冲处理 /
力学性能 /
组织演变 /
位错增殖
Key words
AZ31 magnesium alloy /
electropulsing treatment /
mechanical properties /
microstructural evolution /
dislocation multiplication
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基金
国家自然科学基金青年项目（52204396）; 国家自然科学基金联合基金项目（U24A20119）; 太原科技大学科研启动基金项目（20222087）
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