Hot deformation behavior and processing map of a powder metallurgy Ti–22Al–25Nb alloy

• Published in: Journal of alloys and compounds Vol. 600; pp. 215 - 221
• Main Authors: Jia, Jianbo, Zhang, Kaifeng, Liu, Liming, Wu, Fuyao
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 05.07.2014; Elsevier
• Subjects: Alloy powders; Applied sciences; Billets; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Deformation; Dynamic recrystallization; Elasticity. Plasticity; Exact sciences and technology; Hot pressing; Instability; Instability flow; Kinetic analysis; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; P/M Ti–22Al–25Nb alloy; Physics; Powder metallurgy; Processing maps; Stability; Strain; Titanium base alloys; Treatment of materials and its effects on microstructure and properties; P/M Ti–22Al–25Nb alloy; Kinetic analysis; Processing maps; Dynamic recrystallization; Instability flow; Plastic flow; Compressive testing; Dislocation glide; Niobium alloys; Dynamical recrystallization; Powder metallurgy; Titanium base alloys; Dislocation climb; Hot pressing; Aluminium alloys; Sintering; Kinetics; Atomizing; P/M Ti-22Al-25Nb alloy; Transition element alloys; Strain rate
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.02.116

It can be discovered that the nucleation occurs at trigeminal grain boundary. It is easy for newly formed recrystallized grains to grow owing to large recrystallization driving force, and then necklace-shaped grains with serrated grain boundary form along the elongated grains boundaries. [Display omitted] •A powder metallurgy Ti–22Al–25Nb alloy was fabricated by hot pressed sintering.•Isothermal compression tests of the P/M Ti–22Al–25Nb alloy were performed.•The hot deformation behavior was studied by processing maps and microstructures.•Stability and instability domains were obtained based on the instability parameters.•The deformation mechanisms and microstructures in stability domains were discussed. Powder metallurgy (P/M) Ti–22Al–25Nb alloy billets were fabricated by hot pressing (HP) from argon atomized pre-alloyed powders at a temperature of 1050°C under a pressure of 35MPa, sintering for 1h. Cylindrical specimens from HP’ed billets were compressed within the deformation temperature range of 950–1070°C using strain rates from 0.001 to 1s−1 to a height reduction of 50%. Processing maps at strains of 0.4 and 0.6 were constructed on the basis of dynamic material model (DMM) theory by using the flow stress data obtained from hot compression tests. The processing map at a strain of 0.6 reveals a single dynamic recrystallization (DRX) domain and three lamellar globularization domains. Furthermore, an instability region is exhibited at temperatures lower than 980°C and strain rates higher than 0.1s−1. The hot deformation behavior regimes represented by DRX, lamellar globularization and the instability flow have been discussed in reference to microstructural evolution during hot compression. Kinetic analysis of the flow stress data at a strain of 0.6 was investigated. The results indicate that dislocation slip and climb (DSC) are likely to be the deformation mechanism responsible for the stability domains.