激光熔修AZ31B镁合金焊趾区材料的疲劳性能  

Investigation of Fatigue Property of Welded Toes On Magnesium AZ31B Alloy By Laser Dressing Method

作　　者：李正[1] 吴圣川[1] 徐道荣[1] 王文先[2] 

机构地区：[1]合肥工业大学材料科学与工程学院先进材料连接与仿真中心,合肥230009 [2]太原理工大学材料科学与工程学院,太原030024

出　　处：《失效分析与预防》2011年第4期209-212,共4页Failure Analysis and Prevention

基　　金：国家自然科学基金(51005068);汽车车身先进设计制造国家重点实验室基金(30915005)

摘　　要：疲劳性能是评估镁合金焊接结构寿命的重要指标。AZ31B镁合金TIG焊趾存在的微细裂纹与几何不连续,是在役焊接结构疲劳裂纹萌生的主要原因。为减轻接头的应力集中和改善其疲劳性能,采用CO2激光热源重熔AZ31B镁合金焊趾。研究发现:Mg17Al12在近熔合线的热影响区中沿晶界析出,而在焊缝中呈弥散分布。此外,因受脆晶相的作用,热影响区存在着微细裂纹。激光熔修能细化热影响区晶粒,抑制了Mg17A12沿晶界的析出从而有利于消除热影响区裂纹。然而因激光功率密度过高引起的镁元素烧损,是导致疲劳性能下降的一个重要原因。Fatigue property is the key indicator to evaluate the service life of magnesium welded-structures.There exists minor cracks and geometric uncontinuity at the welded toe,which severely degrades the service performance and life of the structure as well as the objective reason of joints cracks.To reduce the extent of stress intensity and improve the fatigue property of welded joints of magnesium AZ31B,the CO2 laser is introduced to dress the TIG joints of toes.Results imply that the Mg 17 Al 12 precipitates along crystal boundary on HAZ near fusion line, while at the middle of weld seam it exhibits a diffuse distribution.The laser dressing can inhibit the separation of Mg 17 Al 12,and the fined crystal grain can also be achieved at the HAZ.Unfortunately,it is the uneven surface of weld toe caused by the Mg burning that severely deteriorates the fatigue properties of Mg welded joints.

关 键 词：镁合金 疲劳性能 焊趾 激光熔修 应力集中 

分 类 号：TG405[金属学及工艺—焊接]