TEXTURE EVOLUTION IN BORON MODIFIED TI-6AL-4V ALLOY

摘要

Owing to their high strength-to-weight ratio, excellent mechanical properties and corrosion resistance, titanium (Ti) and its alloys, especially (α+β) alloys like Ti-6A1-4V is the backbone materials for aerospace, energy, and chemical industries. Trace boron addition (～0.1 wt. %) to the alloy Ti-6A1-4V produces a reduction in as-cast grain size by roughly an order of magnitude resulting in enhanced ductility, higher stiffness, strength and good fracture resistance. Boron addition could also affect the evolution of texture and microstructure in the material. The solidification microstructures of Boron free as well as Boron containing Ti-6A1-4V are found to be almost homogeneous from periphery towards the center of as-cast ingot in terms of both a-colony size and distribution. Boron addition substantially reduces a-colony size (～50-80 μm). A gradual change in a texture from periphery towards the center has been observed with orientations close to specific texture components suggesting the formation of texture zones. The mechanism of texture evolution can be visualized as a result of variant selection during solidification through (α+β) phase field.