Effects of Hot-Rolled Process and Heat Treatment on Microstructure and Mechanical Properties of Ti-6Al-4V ELI Alloy

Abstract

The properties of titanium alloys significantly depend on the microstructure, which are correspond to the deformation conditions. However, because of its low thermal conductivity, sensitive to deformation temperature, narrow stable regions for hot working and structural heterogeneity, it does not achieve cosmically industrial production and application. In this paper, the effects of hot rolling deformation in single-phase (β) region, cross-phase region and heat treatment on the microstructure and mechanical properties of Ti-6Al-4V ELI alloy were systematically investigated. The relationship between microstructure and properties of alloy was also analyzed in order to a theoretical basis for the development of the rolling technology for the manufacture. The results indicated that hot rolling deformation in different region had significant effects on microstructure heterogeneity (the size and colony of α phase, lamellar microstructure of β transformed). It has been shown that fine and coarse lamellar α structure within grains and visible grain boundary α were characterized after the deformation above the β transformation temperature, which made high impact toughness. But in order to ensure in single phase region, the heat preservation method after passes of rolling may cause β grain coarsening (widmanstatten structure), leading to mechanical properties worsen. The fine crisscross substructures of α phase was obtained after deformation in cross-phase region, improving good mechanical properties. After solution treatment followed aging, the uniform type of microstructure was reached, which mainly displayed the change of contents and sizes of lamellar α phase.