ZL108镍基粉末激光表面合金化气孔与裂纹的研究  

Study of the porosity and cracks during laser surface alloying of cast ZL108 aluminium alloy with Ni-base alloy powder

作　　者：王福德[1] 胡乾午[1] 曾晓雁[1] 

机构地区：[1]华中科技大学激光国家重点实验室,武汉430074

出　　处：《应用激光》2004年第5期265-268,319,共5页Applied Laser

基　　金：湖北省博士后基金 (2 0 0 2 - 3)资助

摘　　要：ZL10 8表面镍基粉末激光合金化的实验研究表明 :激光合金化层的显微组织由两部分组成 ,与基体金属交界处是垂直于熔合线生长的具有定向凝固特征的树枝状晶 ,合金化区是细小的等轴状晶。在树枝状晶相邻间的凹陷处和基体金属未熔化晶粒的界面上最有可能产生气泡核 ,熔池保护不良 ,合金粉末或粘接剂中残存水分 ,均是影响气泡生成的主要因素。对于合金层中的裂纹 ,主要是在熔池凝固末期 ,已凝固合金化层金属塑性不足并在残余拉应力作用下造成的低塑性脆化裂纹。The study of laser surface alloying on Ni-based alloy powder cast ZL108 aluminum alloy showed that the microstructure of the laser-alloying layer was made up of two different zones. At the bottom of the interface between the alloyed layer and the substrate was the dendrite morphology with character of directional solidification and at the middle and upper layer the dendrite space was decreasing rapidly to form a fine equiaxial structure. At the hollow between two-neighbor dendrite and the interface between the alloyed layer and the substrate aluminum alloy, it was most likely to form nucleus of bubble. The bubble was very difficult to float out of alloyed layer owing to the excellent thermal diffusivity, as well as the high-speed of solidification of aluminum alloy. The bad shielding gas of the melting pool and the residue water in the binder are the most important factors that affect the form of pores in the cladding metal. The cracks occurred in the laser alloyed layer was owing to the residue stress and less of plasticity during the end period of solidification. The cracks were one kind of cold crack named low plastic and brittle crack.

关 键 词：基体金属 激光表面合金化 熔池 镍基 凝固 气孔 裂纹 晶相 粉末 气泡 

分 类 号：TN304[电子电信—物理电子学] TG174[金属学及工艺—金属表面处理]