激光冲击强化7075铝合金熔焊接头的疲劳性能  

Fatigue performance of laser shock processed fusion welded 7075 Al alloy

作　　者：王连庆[1] 胡雅楠[2] 车志刚 吴圣川[2] WANG Lianqing;HU Ya'nan;CHE Zhigang;WU Shengchuan(State Key Laboratory for Advanced Metals&Materials,University of Science and Technology Beijing,Beijing 100083,China;State Key Laboratory of Traction Power,Southwest Jiaotong University,Chengdu 610031,China;Science and Technology on Power Beam Processes Laboratory,AVIC Manufacturing Technology Institute,Beijing 100024,China;Aviation Key Laboratory of Science and Technology on Advanced Surface Engineering,AVIC Manufacturing Technology Institute,Beijing 100024,China)

机构地区：[1]北京科技大学新金属材料国家重点实验室,北京100083 [2]西南交通大学牵引动力国家重点实验室,成都610031 [3]中国航空制造技术研究院高能束流加工技术重点实验室,北京100024 [4]中国航空制造技术研究院先进表面工程技术航空科技重点实验室,北京100024

出　　处：《航空学报》2021年第5期267-274,共8页Acta Aeronautica et Astronautica Sinica

基　　金：国家自然科学基金大科学装置联合基金培育项目(U2032121);国家自然科学基金(5187051990);民用飞机专项科研项目(MJ-2016-F-16)。

摘　　要：激光冲击强化(LSP)技术具有残余压应力场深、冷作硬化程度低和强化区域可控等优点,在焊接结构表面改性方面应用前景广阔。对2 mm厚度的7075-T6铝合金激光-电弧复合焊接接头实施了激光冲击强化处理,对比分析了强化前后接头的硬度、残余应力、疲劳寿命以及疲劳裂纹形核机制。结果表明,焊缝中心的最高硬度由强化前的152 HV提高到强化后的175 HV,有效强化层深度约为100μm;经激光冲击强化后,焊缝区呈现残余压缩应力,最大残余压应力为-200 MPa;9组焊接接头试样的平均疲劳寿命为675937周,约为强化前疲劳寿命(262297周)的2.6倍;疲劳裂纹萌生位置从具有高度应力集中的表面缺陷转移至强化层以下的亚表面,进而有效地提高了疲劳裂纹的形核寿命。Laser Shock Processing(LSP)offers deep compressive residual stress layers,low cold work hardening and flexible strengthening regions,drawing extensive attention in surface modification of welded structures.This study examines 2 mm thick 7075-T6 laser-arc hybrid welded joints treated by LSP.The hardness,residual stresses,fatigue life and fatigue crack initiation mechanism of the welded joints before and after LSP are investigated.It is found that the highest hardness in the weld zone increases from 152 HV before LSP to 175 HV after LSP.The effective strengthening layer depth is around 100μm.The weld zone influenced by LSP is primarily characterized by residual compressive stress,with the highest compressive stress value of-200 MPa.The average fatigue life of nine welded joints subjected to LSP is around 675937 cycles,approximately 2.6 times the fatigue life of those without LSP(262297 cycles).The fatigue crack nucleation site is transferred from surface defects with high stress concentration to the subsurface below the strengthening layer,leading to improved fatigue crack initiation life.

关 键 词：激光冲击强化 激光焊接 7075-T6铝合金 残余应力 疲劳寿命 疲劳裂纹萌生 

分 类 号：V261.8[航空宇航科学与技术—航空宇航制造工程]