Abstract
In this paper, the isothermal compressive behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy was investigated on a Gleeble-3500 simulator in the temperature range from 1073 to 1373 K at an interval of 50 K (while the phase transus temperature is approximately 1273 K) and the strain rate range of 0.001–10 s−1. Microstructure evolution and deformation behavior were investigated. The typical flow softening behavior during deformation is observed, which can be explained by the deformation heating effect and microstructure changes. The deformation heating effect is influenced by strain rate and deformation temperature, and it increases with the increasing strain rate and decreasing deformation temperature. In the α + β phase field, the fractions of the primary α phase decrease with the increase of deformation temperature and strain rate. In this case, dynamic recovery may be the main mechanism for microstructure evolution based on the electron back-scatter diffraction (EBSD) analysis. The fully phase transformation occurs above the β transus temperature, which is governed by Burgers orientation relations. The Zener–Hollomon parameter with an exponent-type equation was used to intuitively describe the effects of the deformation temperatures and strain rates on the flow stress behaviors. Furthermore, the influence of strain was incorporated in the constitutive analysis. A fourth-order polynomial was ideally matched to represent the influence of strain. In consequence, the constitutive equation of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy including the phase transus and compensation of the strain was developed based on the experimental results throughout the deformation process. The results indicated that the correlation coefficient (R), root mean square error (RMSE), and the average absolute relative error (AARE) were calculated to be 0.987, 3.585 MPa, and 9.62% in the single-phase region and 0.979, 18.78 MPa, and 9.16% in the duplex-phase region, respectively. Hence, the constitutive model proposed in this research can provide accurate and precise theoretical prediction for the flow stress behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy.
Highlights
Peng et al [9] studied the effect of strain rate, temperature, and strain on the flow behavior for TC4-DT alloy by establishing a constitutive equation with a view to the variation of the material constants affected by strain
Discontinuous yielding is observed at 1323 K. Such behavior is associated with the increasing mobile dislocation at grain boundary, and it is strengthened as the increasing temperature and strain rate [14,15]
It can be considered that the steady flow stress is extremely sensitive to strain rate and temperature, or the occurrence of steady state on the flow stress behavior would be promoted with the increase of deformation temperature, while the value of steady-state stress decreases with the reduction of strain rate
Summary
Peng et al [9] studied the effect of strain rate, temperature, and strain on the flow behavior for TC4-DT alloy by establishing a constitutive equation with a view to the variation of the material constants affected by strain. The relationship between flow stress behavior and phase transformation was mentioned in their work. The above-mentioned research work on duplex phase titanium alloys are worth mentioning for recognizing the flow stress behavior, microstructure, and texture evolution of the material during hot deformation [10,11,12,13]. The main target of the present work is to systematically evaluate the deformation behavior, microstructure changes, and constitutive behavior under a wide range of deformation temperature and strain rate with the consideration of phase transformation. The constitutive model with high prediction accuracy will be established
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
