Microstructural features of friction-welded Ti-6Al-4V joint

Microstructural features of friction-welded Ti-6Al-4V joint have been inves tigated by both optical microscope and transmission electron microscope (TE M). The microstructure of the welded joint is not uniform. It can be classi fied into the phase transformed region(P), the deformed region(D) and the r egion of unchanged base metal(B). In the phase transformed region, the micr ostructure consists of platelike, acicular and equiaxed alpha phase plus be ta phase between them and the dislocations can be observed in some or phase particles. The equiaxed alpha phase mainly distributes in the near center of rod specimen. The quantity of platelike and acicular alpha phase and the size of the grains increase progressively along the radial direction of th e rod type welded joint. In the deformed region, the grains are reoriented and the microstructure consists of the elongated alpha phase containing a l ot of dislocations and intergranular beta phase.