The microstructural evolution and grain growth kinetics of TZ20 alloy during isothermal annealing

Abstract

The microstructural evolution and grain growth kinetics of the hot rolled Ti–20Zr–6.5Al–4V (wt.%, TZ20) alloy during subsequent isothermal annealing were investigated. The XRD results show that the examined alloy is composed of α and β phases after annealing at temperatures from 750 °C to 850°C. The SEM results show that the microstructure of all annealed specimens is typical basketweave structure with interlaced α plates embedded in β matrix. Thickness growth kinetics of α plate in TZ20 alloy was investigated by designing various heat treatments. The grain growth exponent n, pre-exponential factor K0 and activation energy of boundary migration E of TZ20 alloy during isothermal annealing were determined. Finally, the relationship between thickness increment Δh, annealing temperature T and holding time t of isothermal annealed TZ20 alloy has been deduced. Mechanical properties of the examined alloy with various annealing treatments were also investigated. Tensile results show that the strength changes in the range of 1120MPa to 1246MPa, and the ductility in term of elongation varies from 9.1% to 14.3%. The relation between mechanical properties and microstructure was also discussed. This work is of great significance to guide the manufacture and to promote practical applications of TiZr-based alloys.