激光快速成形TC21钛合金沉积态组织研究  

Research on Microstructures of Deposited TC21 Titanium Alloy by Laser Rapid Forming

作　　者：昝林[1] 陈静[1] 林鑫[1] 张小红[1] 黄卫东[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《稀有金属材料与工程》2007年第4期612-616,共5页Rare Metal Materials and Engineering

基　　金：国家自然科学基金重点项目(50331010)

摘　　要：分别采用光学显微镜、扫描电子显微镜、X射线衍射和显微硬度等测试手段,研究了激光快速成形高强高韧损伤容限型TC21钛合金的沉积态组织。结果表明:TC21沉积态有着粗大的沿沉积高度方向外延生长的原始β柱状晶,仅最后一层熔覆层顶部为较细小的β等轴晶。宏观上存在明暗两个组织区域,明区为针状马氏体区,位于最后十几层熔覆层,暗区为网篮组织区。结合成形过程传热和组织转变理论分析认为,网篮组织是由明区的初始快冷凝固的马氏体在成形过程中,经受再热循环的固溶时效作用转变而来。随着激光功率的增大,原始β柱状晶将粗化,暗区网篮组织中片状α亦将长大;明区硬度基本不变,暗区硬度略有下降。The microstructures of deposited TC21 titanium alloy with high strength, high toughness and high damage-tolerance by laser rapid forming （LRF）were studied with Optical Microscopy （OM）, Scanning Electronic Microscopy （SEM）, X-Ray Diffraction （XRD） and micro-hardness test. The results show that the prior B grains in the deposited TC21 are coarse and columnar for the epitaxial growth with some smaller equiaxed β grains in the top of last layer. Macro-image reveals that two different microstructure areas existed in the deposited TC21： the bright area of acicular martensite located in the last more than 10 layers; and the dark area of basket-weave. By the theory of heat flux in the processing and microstructure transformation, it can be concluded that the basket-weave microstructure is transformed from the initial rapid-solidification martensite of bright area through solid solution and aging treatment by reheat cycles during the LRF process. With the increase of the laser power, the prior columnar β grains become coarser and the a lamellaes in the dark area with basket-weave microstructure grow up. Meanwhile, the micro-hardness keeps constant for the bright area, but descends slightly for the dark area.

关 键 词：TC21钛合金 激光快速成形 显微组织 显微硬度 

分 类 号：TG146.23[一般工业技术—材料科学与工程]