Production of Submicron-Grained Ti-6Al-4V Sheets with Enhanced Superplastic Properties

摘要

The availability to produce Ti-6Al-4V sheet material with submicron-grained microstructure for superplastic forming (SPF) and superplastic forming/diffusion bonding (SPF/DB) applications will be reported. The sheets (a grain size of 0.3-0.5 μm) were produced by pack rolling manufacturing technique of the blanks with pre-formed submicrocrystalline (SMC) structure. The sheets possessed isotropic mechanical properties in the sheet plane and higher yield strength, ultimate tensile strength and fatigue limit than that of conventional sheet with the grain size of 3-6 μm. At exceptionally low temperature range of 650-750℃ SMC sheets demonstrated enhanced superplastic properties, which are defined as an initial flow stress of 15-30 MPa at the strain rates of 3x10~(-4)-7x10~(-4)/s, and also achieves about 1000% elongation at the temperature of 750℃. The sheet material with SMC structure is characterized by well formability and acceptable solid-state weldability under low temperature superplastic conditions. The commercial advantage of this reduced grain sized material will be discussed.