High-Temperature-Tensile-Deformation Behavior of Ti-6Al-4V Alloy with the Acicular α′ Martensite Microstructure

Abstract

Titanium alloys are widely used in aerospace components, with the most widely used alloy being (α+β)-type Ti-6Al-4V (hereafter designated as Ti-64) alloy owing to its high specific strength and high formability associated with superplasticity. This work examines the tensile deformation behavior of the Ti-64 alloy with the acicular α′ martensite microstructure tested at from 700°C to 900°C. Higher tensile-elongation and higher strain-rate-sensitivity value are seen in the Ti-64 alloy with the α′ martensite microstructure as compared to that with the lamellar (α+β) microstructure. During deformation of the α′ martensite microstructure at 700°C or 800°C, acicular microstructure evolves into fine equiaxed (α+β) structure, whereas there is no apparent change in microstructure in the case of the lamellar (α+β) starting microstructure. This result indicates that dynamic globularization during deformation is strongly enhanced in the acicular α′ martensite starting microstructure, thereby leading to higher tensile elongation.