脉冲电流对AZ91镁合金温挤压过程中动态析出和微观组织的影响  

Effect of Electropulse on Dynamic Precipitation and Microstructure of AZ91 Magnesium Alloy During Warm Extrusion

作　　者：王彬杉 徐光 任睿 张强[1,2,3] 单召辉 樊建锋 WANG Binshan;XU Guang;REN Rui;ZHANG Qiang;SHAN Zhaohui;FAN Jianfeng(Key Laboratory of Interface Science and Engineering in Advanced Materials,Ministry of Education,Taiyuan University of Technology,Taiyuan 030024,China;College of Materials Science and Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Shanxi Key Laboratory of Advanced Magnesium Based Materials,Taiyuan University of Technology,Taiyuan 030024,China;College of Physics and Optoelectronics,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]太原理工大学新材料界面科学与工程教育部重点实验室,太原030024 [2]太原理工大学材料科学与工程学院,太原030024 [3]太原理工大学镁基材料山西省重点实验室,太原030024 [4]太原理工大学物理与光电学院,太原030024

出　　处：《金属学报》2025年第1期129-142,共14页Acta Metallurgica Sinica

基　　金：山西省自然科学基金项目Nos.20210302123134、202203021221071和202203021211157;山西省留学委员会项目No.2022-045;山西浙大研究院新材料与化工研究院基础研究项目No.2021SX-FR005。

摘　　要：脉冲电流辅助成形工艺具有提高成型能力及细化微观组织等优点,被广泛用到各种塑性变形过程中。然而,关于脉冲电流在动态挤压变形过程中的作用尚不明确。本工作利用脉冲电流辅助挤压(EPAE)技术,研究了脉冲电流对于AZ91镁合金挤压过程中动态析出和微观组织的影响。结果表明,在能够完全动态再结晶(DRX)的临界变形条件下,EPAE工艺可以降低AZ91镁合金挤压过程中β-Mg_(17)Al_(12)相的体积分数并促使其发生球化,同时能够促进平均晶粒尺寸和最大基面织构强度的增加,且峰值电流密度越高,效果越明显。与常规热挤压相比,峰值电流密度为6.4×10^(7) A/m^(2)的EPAE工艺促使AZ91镁合金中β-Mg_(17)Al_(12)相的体积分数从76.9%降低至16.5%,平均晶粒尺寸从1.07μm增加至3.54μm,最大织构强度从3.39增加至5.92。在不均匀分布的β-Mg_(17)Al_(12)相的钉扎作用下,最终EPAE态AZ91镁合金内部形成双峰组织。实验及理论分析表明,脉冲电流中热效应和非热效应的共同作用所导致的AZ91镁合金挤压过程中的Gibbs自由能变化量和原子扩散通量的提高是上述实验现象发生的主要原因,在促进了β-Mg_(17)Al_(12)相的溶解及其附近Al溶质原子均匀分布的同时提高了晶界迁移速率。同时,脉冲电流可以通过其漂移电子对基面滑移的加速作用促进β-Mg_(17)Al_(12)相颗粒贫乏区中晶粒的旋转。The electropulse-assisted forming process has been widely used in various plastic deformation applications owing to its advantages in improving formability and refining microstructure.However,the influence of electropulse on the dynamic extrusion deformation process remains unclear.In this study,the effects of electropulse on dynamic precipitation and microstructure evolution of AZ91 magnesium alloy during extrusion were investigated using electropulse-assisted extrusion(EPAE)technology.The results demonstrate that under critical deformation conditions for complete dynamic recrystallization,the EPAE process reduces the volume fraction of the β-Mg_(17)Al_(12) phase,promotes its spheroidization,and enhances both the average grain size and the maximum basal texture intensity.These effects become more pronounced with increasing peak current density.Specifically,with a peak current density of 6.4×10^(7) A/m^(2) during the EPAE process,the volume fraction of the β-Mg_(17)Al_(12) phase decreased from 76.9% to 16.5%,the average grain size increased from 1.07μm to 3.54μm,and the maximum basal texture intensity increased from 3.39 to 5.92,compared to conventional hot extrusion.The bimodal structure observed in the EPAE-processed AZ91 alloy was attributed to the pinning effect caused by the inhomogeneous distribution of the β-Mg_(17)Al_(12) phase.Experimental and theoretical analyses indicated that the increase of Gibbs free energy variation and atomic diffusion flux during extrusion of AZ91 alloy caused by the combined thermal and athermal effects of the pulsed current was the main reason for the experimental phenomena,which promoting the solution of β-Mg_(17)Al_(12) phase and uniform distribution of Al solute atoms nearby while also increasing the grain boundary migration rate.Moreover,the electropulse strengthened the basal texture in β-Mg_(17)Al_(12) particle-depleted regions by accelerating basalslip.

关 键 词：AZ91 镁合金 脉冲电流辅助挤压 β-Mg_(17)Al_(12)相 动态析出 晶粒长大 

分 类 号：TG146.2[一般工业技术—材料科学与工程]