激光熔化沉积Ti_(2)AlNb基合金凝固组织研究

Research on Solidified Structure of Laser Melting Deposited Ti_(2)AlNb-based Alloy

采用激光熔透化沉积技术制备了Ti_(2)AlNb基合金块状试样,利用光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)表征手段分析了激光熔化沉积Ti_(2)AlNb基合金的组织形貌,测定了试样的显微硬度。结果表明:Ti_(2)AlNb基合金样品yoz面(横截面)晶粒形貌为相邻焊道搭接区的贯穿多层的大柱状晶和非搭接区的小柱状晶和小等轴晶组成的“指节状”形貌在三维空间上交替排列。显微组织主要由B2+O两相组成,距顶层约9 mm区域内为这两相构成的超细网篮组织,显微硬度达到430 HV,以下区域为普通网篮组织,显微硬度约为380 HV。

The Ti_(2)AlNb-based alloy bulk specimen was prepared by laser melting deposition. The corresponding microstructure of the alloy was systematically characterized by means of optical microscopy(OM), X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The microhardness of the specimen was also tested. The results show that the microstructure of yoz surface(cross section) of the laser melting deposited Ti_(2)AlNb-based alloy exhibits an alternative arrangement of coarse columnar crystals penetrated several layers in the overlap area and knuckle-like crystals composed of small columnar and small equiaxed grains in other regions. The microstructure is primarily composed of B2 and O phases. Meanwhile, an ultra-fine "basket-weave" microstructure is within the region about 9mm away from the top, the microhardness of the region is 430 HV. The other region’s structure is a common "basket weave" structure with the microhardness of 380HV.