表面技术2025，Vol.54Issue(17)：137-149,13.DOI:10.16490/j.cnki.issn.1001-3660.2025.17.012
脉冲电流对AZ31镁合金激光冲击强化效果的影响
Effect of Pulse Current on Laser Shock Peening Result of AZ31 Mg Alloy
摘要
Abstract
As the lightest commercially structural metallic materials,Mg and its alloys have become the preferred materials for lightweight design and energy saving in aerospace,automobiles,and 3C industries,due to their low density,high specific strength and specific stiffness,and superior damping performance.However,the applications of Mg alloys are limited due to their low absolute strength,poor formability,and unsatisfactory tensile properties.These drawbacks also make them difficult to be processed.Whereas the existing strengthening methods often sacrifice plasticity as a price.Surface modification has been widely employed to enhance the functional properties of structural components,and laser shock peening(LSP)stands out due to its unparalleled advantages over other surface modification techniques.LSP is an established surface modification technique used to improve the surface integrity and related properties of materials.However,for materials with high strength and hardness as well as large thickness,its effectiveness may be compromised with the single mechanical field.Electropulsing-assisted laser shock peening(EP-LSP)has great potential for enhancing the process results of LSP by employing an extra electric field.In this work,EP-LSP is adopted to improve the surface integrity,mechanical properties and microstructure of AZ31 Mg alloy sheets.The process efficiency of the pretreatment mode(LSP after electropulsing)and the online mode(LSP when electropulsing)is examined in detail and related mechanisms are discussed.The surface morphology analysis,microhardness and surface residual stress measurements,room temperature uniaxial tensile tests and fracture morphology analysis,optical microscope observation and electron back-scatterred diffraction analysis are carried out.The results show that the alloy experiences gradual increase of temperature with pulse current density and the maximum 177.1 ℃ within gauge region is obtained with 90 A/mm2.The surface roughness in the pretreatment mode of EP-LSP is about 9.1 μm,and the sample surface in the online mode displays more uniform distribution of pits and relatively low roughness of about 7.5 μm.The cross-sectional hardness increases from the initial 48.12HV to 83.90HV after LSP,and both the surface and cross-sectional hardness are improved to above 80HV by EP-LSP.The surface residual stress of as-annealed samples is modified from the initially tensile state of about 24.8 MPa to the compressive state of about-40.0 MPa after EP-LSP.The case is slightly more obvious in the online mode than the pretreatment mode whereas the influence of pulse current density is negligible.The optimum tensile properties are achieved after EP-LSP with 60 A/mm2 and the elongation to failure is maintained at an acceptable level while keeping the strengthening results.The tensile strength and yield strength of EP+LSP samples are 306.2 MPa and 273.5 MPa,and those of EPLSP samples are 298.3 MPa and 269.5 MPa,respectively.The elongation to failure is 11.2％and 18.7％for EP+LSP and EPLSP samples,respectively.The fracture surface morphology transforms from the typical brittle fracture mode after LSP to a mixed ductile-brittle mode dominated by ductile fracture after EP-LSP.Under the condition of electro-thermal-mechanical multi-field coupling,owing to the thermal effect and athermal effect such as electron wind from pulse current,the surface integrity of the alloy samples is improved by EP-LSP,the dynamic recovery and recrystallization processes are promoted,the fraction of high-angle grain boundaries is increased,the grain refinement result is enhanced,the level of residual compressive stress is further raised,and the mechanical properties are significantly improved.This work reveals the effect rule and mechanism of pulse current on LSP and provides data support for the practical application and promotion of EP-LSP technique especially in Mg alloys and has important theoretical significance and practical value.关键词
激光冲击强化/脉冲电流/表面完整性/力学性能/微观组织/AZ31镁合金Key words
laser shock peening/pulse current/surface integrity/mechanical properties/microstructure/AZ31 Mg alloy分类
信息技术与安全科学引用本文复制引用
李进,胡鸿彪,李博文,王文泉,赵新甜,郑宏宇,王宗申..脉冲电流对AZ31镁合金激光冲击强化效果的影响[J].表面技术,2025,54(17):137-149,13.基金项目
国家自然科学基金(51605266) （51605266）
山东省自然科学基金(ZR2022ZD07,ZR2023ME134) （ZR2022ZD07,ZR2023ME134）
山东省高等学校青创科技支持计划(2021KJ068)National Natural Science Foundation of China(51605266) （2021KJ068）
Shandong Provincial Natural Science Foundation(ZR2022ZD07,ZR2023ME134) （ZR2022ZD07,ZR2023ME134）
Scientific Innovation Project for Young Scientists in Shandong Provincial Universities(2021KJ068) （2021KJ068）
