Structural refinement of α-β polymorphs in Ti-6Al-4V alloy

A new analytical procedure for the processing of XRD patterns with conventional powder geometry was used to study phase composition and properties of a typical α-β Ti alloy. This approach was particularly effective in studying the Ti-6Al-4V alloy, since the small amount of β phase can not be easily identified by traditional XRD methods. In addition to quantitative phase analysis, relevant structural information was produced by the refinement of cell parameters, thermal factors, and atomic positions. Further microstructural information, including texture, crystallite domain size, and distortion from lattice defects, was also obtained with the same procedure. The proposed method was particularly useful in studying the effect of surface polishing, which produced a compressive residual stress (also measured by non-destructive XRD techniques) of - 450 MPa in the surface region; changes in the microstructure and chemical composition of alloy elements in the two Ti polymorphs after stress relief heat treatment were also studied in detail.