Phase composition and microanalysis of TiAl-Based alloys sheet by electron beam-physical vapor deposition

TiAl-based alloys sheet of 150 mm x 100 rum in size were successfully fabricated by electron beam-physical vapor deposition (EB-PVD) process. The phase composition and microscopic morphology were analyzed by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffractometer (XRD) for the as-deposited, as-annealed or as-pressed samples, respectively. The results show that the as-deposited sample of TiAl-based alloys sheet is composed of gamma, alpha(2) and tau phases with a gradient component change, leading to the spontaneous delamination. The microstructure of as-deposited sheet is of columnar crystals. The columnar crystals and tau phase disappeared, and the a2 phase decreased greatly after vacuum annealing treatment at 1000 degrees C for 16 h, and the component tended to be uniform. After vacuum hot pressing treatment at 1250 degrees C for 1 h, the relative density of samples is increased obviously. Compared with the as-deposited samples, the fractographs of as-annealed or as-pressed samples were diverted from the intergranular fracture to the mixed manner of intergranular fracture and cleavage fracture.