AZ91D-T6铸造镁合金激光冲击强化和高周疲劳性能研究  

Study on High Cycle Fatigue Properties and Laser Shock Processing of AZ91D-T6 Cast Magnesium Alloy

作　　者：张青来[1] 吴铁丹 钱阳[1] 王荣[1] 洪妍鑫 陈骏[1] 

机构地区：[1]江苏大学材料科学与工程学院,江苏镇江212013

出　　处：《中国激光》2014年第10期87-93,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(51175231)

摘　　要：为了研究激光冲击对AZ91D-T6铸造镁合金高周疲劳性能的影响,采用钕玻璃脉冲激光器(波长1064nm,脉冲宽度20ns),对中心缺口试样进行激光冲击强化(LSP)处理,并进行了拉-拉疲劳试验,分析了表面形貌、表面显微硬度、微观组织、疲劳断口特征和残余应力分布,结果表明:以1.5GW/cm2功率密度和光斑50%搭接的激光冲击强化后,中心缺口疲劳试样上下表面形成高残余压应力,显微硬度提高24%左右,晶粒明显细化,冲击试样循环周次比未冲击的提高33.7%,疲劳断口呈解理断裂特征,主要表现为大量解理台阶和河流花样,β-Mg17Al12相的存在改变了疲劳裂纹扩展路径。激光冲击延迟了裂纹萌生时间,提高了AZ91D-T6铸造镁合金的疲劳寿命。In order to study the effect of laser shock processing（LSP）on the high cycle fatigue properties of AZ91DT6 cast magnesium alloy,the test samples with center hole are shocked with Nd：glass laser with the wavelength of1064 nm and pulse width of 20 ns.Tensile-tensile fatigue test is also carried out on the samples.The surface morphology,surface micro-hardness,microstructures,fatigue fracture characteristics and residual stress are analyzed.The results show that after LSP with power density of 1.5 GW/cm^2 and spots of 50% overlap rate,high residual compressive stress is generated on the upper and lower surface of the fatigue samples.The micro-hardness of shocking area increases by about 24% and the grains are refined obviously.Fatigue life of the shocked samples is improved by 33.7%than that of the un-shocked samples.The Fatigue fractures show characteristics of the cleavage fracture,and the cleavage steps and river pattern are mainly observed.The crack propagation path is changed because of the existence of theβ-Mg17Al12 phase.The crack initiation time is delayed after LSP,which improves the fatigue life of AZ91D-T6 cast magnesium alloy.

关 键 词：材料 镁合金 激光冲击强化 疲劳性能 残余应力 微观组织 

分 类 号：TN249[电子电信—物理电子学] TG146.22[一般工业技术—材料科学与工程]