Dynamic Softening and Hardening Behavior and the Micro-Mechanism of a TC31 High Temperature Titanium Alloy Sheet within Hot Deformation

Abstract

TC31 is a new type of α+β dual phase high temperature titanium alloy, which has a high specific strength and creep resistance at temperatures from 650 °C to 700 °C. It has become one of the competitive candidates for the skin and air inlet components of hypersonic aircraft. However, it is very difficult to obtain the best forming windows for TC31 and to form the corresponding complex thin-walled components. In this paper, high temperature tensile tests were carried out at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.001 s−1 to 0.1 s−1, and the microstructures before and after deformation were characterized by an optical microscope, scanning electron microscope, and electron back-scatter diffraction. The dynamic softening and hardening behaviors and the corresponding micro-mechanisms of a TC31 titanium alloy sheet within hot deformation were systematically studied. The effects of deformation temperature, strain rate, and strain on microstructure evolution were revealed. The results show that the dynamic softening and hardening of the material depended on the deformation temperature and strain rate, and changed dynamically with the strain. Obvious softening occurred during hot tensile deformation at a temperature of 850 °C and a strain rate of 0.001 s−1~0.1 s−1, which was mainly caused by void damage, deformation heat, and dynamic recrystallization. Quasi-steady flowing was observed when it was deformed at a temperature of 950 °C~1000 °C and a strain rate of 0.001 s−1~0.01 s−1 due to the relative balance between the dynamic softening and hardening. Dynamic hardening occurred slightly with a strain rate of 0.001 s−1. Mechanisms of dynamic recrystallization transformed from continuous dynamic recrystallization to discontinuous dynamic recrystallization with the increase in strain when it was deformed at a temperature of 950 °C and a strain rate of 0.01 s−1. The grain size also decreased gradually due to the dynamic recrystallization, which provided an optimal forming condition for manufacturing thin-walled components with the desired microstructure and an excellent performance.

Modeling of constitutive behavior and ductile fracture of AA5A06 aluminum alloy sheet in warm hydroforming process

“…The objective of this section is to establish a modified Misiolek-based constitutive relationship of the studied metal sheet and to obtain the optimized values for each parameter. To simplify the final expressions of the proposed constitutive model and to reduce the computational error in programing procedures in later sections., here the values of the forming temperature T and strain rate _ e are converted to j and h. The expressions of j and h are given by equation (3).…”

“…However, the mechanical response (e.g. hardening rules and forming limit) of these lightweight materials is very sensitive to the change of temperature and strain rate and usually exhibits obvious work-softening behavior at elevated temperatures [1][2][3] which greatly increase the difficulty of numerical simulation procedure associated with forming processes. To establish practical and reliable numerical models representing temperatureand rate-sensitive lightweight materials is becoming one of the mainly focuses in plastic forming area which is the main concentration in this study.…”

Forming Analysis and Heat Treatment of TC31 Titanium Alloy Component with High Ribs and Thin Webs

“…TC31 titanium alloy, a new high-temperature dual-phase (α + β) titanium alloy of the Ti-Al-Sn-Zr-Nb-Mo-W-Si system, can be used in a temperature range from 650 °C to 700 °C [ 4 , 5 ]. Because the alloy has good durability and creep property under high load and high temperature, it has shown good application in aerospace field [ 6 , 7 , 8 ]. However, titanium alloys have high strength and low ductility at room temperature, so they usually need to be heated to form [ 9 , 10 ].…”

Phenomenological model of hardening and flow for Ti-6Al-4 V titanium alloy sheets under hot forming conditions

“…Then, it is difficult to know which hardening dominants at a given forming condition, and unable to adjust process parameters accordingly. In addition, for hot forming titanium alloy sheets, the dynamic softening due to void damage, grain boundary slip, deformation heat, and dynamic recrystallization normally occurs [15], which makes the above difficulty in quantification more complicated. Therefore, with an efficient and straightforward model for mathematically describing coupled hardening and softening of titanium alloy sheets of process variable control to maximize the deformation uniformity is urgently required.…”