Research on Solidified Structure of Laser Melting Deposited Ti₂AlNb-based Alloy

The Ti₂AlNb-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 Ti₂AlNb-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 9 mm 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.