激光冲击处理对AZ31B镁合金焊接件抗应力腐蚀的影响  

Effect of Laser Shock Processing on Resistance to Stress Corrosion Cracking of Tungsten Inert-Gas Welded AZ31B Magnesium Alloy

作　　者：葛茂忠[1,2] 项建云[1,2] 张永康[1] 

机构地区：[1]江苏大学机械工程学院,江苏镇江212013 [2]常州轻工职业技术学院模具系,江苏常州213164

出　　处：《中国激光》2012年第12期85-91,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(50735001;50675089;50975127)资助课题

摘　　要：为了研究激光冲击处理对镁合金焊接件应力腐蚀性能的影响,采用激光波长1064nm,脉冲宽度15ns,脉冲能量4J,光斑直径3mm的钕玻璃脉冲激光器,对AZ31B镁合金交流氩弧焊接件表面进行冲击处理。室温下采用三点加载的方式,在去离子水中对试样进行应力腐蚀实验。利用光学显微镜和透射电镜观测激光冲击试样微观结构,利用扫描电镜观测应力腐蚀断口。实验结果表明:根据优化的激光参数,能在试样表面制得纳米结构表层,样品表面纳米晶粒大小为35nm左右;激光冲击处理改变了试样表面的应力状态,由残余拉应力60MPa转变为残余压应力-125MPa;激光冲击处理后自腐蚀电位增大88mV,腐蚀电流减小了73.4%,从而降低试样腐蚀倾向;未激光冲击的试样在浸没了192h后出现应力腐蚀开裂,而激光冲击的试样在浸没了10个月后未出现裂纹,这表明激光冲击处理能够提高AZ31B镁合金焊接件抗应力腐蚀的能力。In order to study the effect of laser shock processing （LSP） on the stress corrosion cracking （SCC） of welded magnesium alloy, tungsten inert-gas （TIG） welded AZ31B magnesium alloy sheets surface is processed using Nd.＇YAG laser with a wavelength of 1064 rim, a pulse width of 16 ns, a pulse energy of 4 J and a spot diameter of 3 mm. At room temperature, the SCC susceptibility of the weldment samples with and without laser treatment is assessed by three points loading method in deionized water. The microstructure of specimens by LSP and fracture surfaces are analyzed by optical microscopy （OM）, transmission electron microscope （TEM） and scanning electron microscope （SEM）, respectively. The results show that a nanostructured surface layer can be produced on welded AZ31B Mg alloys by using optimized laser parameters and surface nano grain size is about 35 nm. The surface residual stress is converted from tensile stress （60 MPa） to compressive stress （--125 MPa）. LSP can reduce the corrosion trend of the weldment samples because corrosion potential increases by 88 mV and corrosion current decreases by 73.4 % as compared to the samples without LSP. SCC appeares on samples without laser treatment after 192 h of immersion, however, no cracks is observed on samples treated by laser after 10 months, which shows that LSP can obviously improve the resistance to stress corrosion cracking of TIG welded AZ31B magnesium alloy.

关 键 词：激光技术 激光冲击处理 AZ31B镁合金 交流氩弧焊 纳米结构表层 残余压应力 应力腐蚀开裂 

分 类 号：TN249[电子电信—物理电子学] TG156.99[金属学及工艺—热处理]