Microstructural evolution in Ti-37 mol%Nb alloy under uniaxial compression at high temperatures

Abstract

Uniaxial compression tests were performed for Ti-37 mol%Nb alloy at temperatures from 1073 K to 1373 K at strain rates ranging from 10(-1) s(-1) to 10(-3) s(-1) and true strains from -0.5 to -1.4. At lower temperatures and higher strain rates, {001} + {111} double fiber texture evolved. Alternately, at higher temperatures and lower strain rates, recrystallized grains fully covered the matrix. Their grain growth revealed where the textures formed by deformations up to the desired strain of -1.4 exhibit high orientation densities around {001} in accordance with the preferential dynamic grain growth mechanism. The deformation stress (Zener-Hollomon parameter) revealed a good correspondence with deformed structure and texture. Evolution of the {001} fiber texture was due to grain boundary migration, where the {001} grains were much larger than the average grain size, and the grain boundaries were waved in shape. In not only the Ti-Nb alloy with an extremely small atomic size factor but also pure Nb, the predominant recovery of {001} grains during high-temperature deformation promoted preferential dynamic grain growth.