Effects of microstructure characteristics on the mechanical properties and elastic modulus of a new Ti–6Al–2Nb–2Zr–0.4B alloy

Abstract

A new Ti–6Al–2Nb–2Zr–0.4B alloy was prepared via a vacuum arc remelting process. Furthermore, the changes in the microstructure, mechanical properties, and elastic modulus of the alloy during thermal deformation for forging and rolling were studied. The alloy contained α, β, and TiB phases, and there was a particular phase relationship between TiB and the Ti matrix. The TiB phase was mainly long needle-like in the as-cast samples, short rods with a chain-like distribution in the forging structure, and granular and dispersed evenly after rolling. The mechanical properties’ test results show that the ultimate tensile strength, the elongation at break, and impact toughness from the ingot to forging to plate samples increase from 698 MPa, 5%, and 5 J to 814 MPa, 13.5%, and 41 J and then to 838 MPa, 16%, and 48 J, respectively. Conversely, the elastic modulus decreased gradually from 128.8 to 124.3 and finally to 122.2 GPa. Fractography analysis of the samples revealed a completely ductile fracture mode in the plate samples and a mixed mode of brittle and ductile fractures in the forging samples. Conversely, the ingot samples showed a brittle cleavage fracture with a river pattern.