Hot deformation and dynamic recrystallization of a near-beta titanium alloy in the β single phase region. (October 2018)

• Record Type: Journal Article
• Authors: Chuan, Wu; Liang, Huang
• Is Part Of: Vacuum. Volume 156(2018)
• Page Start: 384
• Page End: 401
• Publication Date: 2018-10
• Subjects: Ti55531 titanium alloy -- Deformation behaviors -- Microstructural evolution -- DRX -- Constitutive model; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2018.07.056
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: A new near-β titanium alloy, Ti-5Al-5Mo-5V-3Cr-1Zr (Ti55531), has been widely used in industry due to its relatively wide processing window, high hardenability and strength. This study investigated the deformation and microstructural evolution of the Ti55531 alloy in the β single phase region. Hot compression tests were carried out at temperatures of 860–900 °C and strain rates of 0.001–10 s −1 on a Gleeble-3800D simulator. The metallographic and electron backscatter diffraction (EBSD) techniques were used to analyze the microstructural evolution. The results demonstrate that the stress curves exhibit discontinuous yield and flow softening phenomena, which are very sensitive to temperature and strain. A processing map was developed for this alloy, which shows that the instability increases with the strain. Dynamic recrystallization (DRX) is a typical characteristic in the beta region, which can take place at high temperatures and low strain rates. Based on this analysis, a physically-based deformation constitutive equation and DRX kinetics, critical condition and grain size models were developed. These models were implemented in a DEFORM subroutine to predict the deformation and microstructural evolution of the Ti55531 workpiece during nonisothermal forging. The comparison between the experimental and predicted results shows good agreement, which indicates that the model is reliable and that the subroutine provides an effective tool to predict the deformation and microstructures for industrial production. Highlights: The hot deformation behavior and microstructural evolution of a near beta titanium alloy Ti55531 was investigated by experiments and numerical modeling. The discontinuous yielding, flow softening and DRX are typical characteristics for the Ti55531 alloy in beta region. A physically-based constitutive model was proposed to model the hot deformation and microstructural evolution of the Ti55531 alloy. The constitutive model is efficient to predict the flow stress, DRX grain size and volume fraction of a Ti55531 workpiece during forging.