Deformation behavior and processing maps during isothermal compression of TC21 alloy

Abstract

In this study, isothermal compression tests were conducted at a Gleeble-1500 simulator at deformation temperatures ranging from 1073 to 1283 K, strain rates ranging from 0.01 to 5.00 s⁻¹, and height reductions ranging from 20 % to 60 %. The flow stress and apparent activation energy for deformation and constitutive equation were used to characterize the deformation behavior of TC21 alloy during the isothermal compression. The processing maps combined microstructure observations were established based on dynamic material model (DMM) over a range of strain rates and temperatures. The results show that an initial yield drop is observed above 1203 K or at higher strain rates ranging from 1.00 to 5.00 s⁻¹, and oscillatory flow curves are presented particularly at a strain rate of 5.00 s⁻¹. Strain has some influence on the apparent activation energy for deformation during the isothermal compression of TC21 alloy. The Q-values and microstructure observation confirm that dynamic recrystallization (DRX) occurs in the β single-phase region. The constitutive equation during the isothermal compression of TC21 alloy is developed using the Zener–Hollomon parameter in the exponent-type equation. The maximum and minimum relative errors between the calculated and the experimental flow stress are 14.1 % and 0.3 %, respectively. The peak efficiency of power dissipation at a strain of 0.7 is about 0.51 occurring at a deformation temperature of 1073 K and strain rate of 0.01 s⁻¹, corresponding to an optimal deformation condition of TC21 alloy.