Hot Tensile Deformation Mechanism and Dynamic Softening Behavior of Ti–6Al–4V Alloy with Thick Lamellar Microstructures

Abstract

The deformation mechanisms and dynamic softening behavior of a Ti–6Al–4V alloy with thick lamellar microstructures are studied by uniaxial hot tensile tests. The true stress first rapidly reaches a peak value because of the rapid dislocations proliferation and tangle, and then gradually decreases due to the dynamic softening with raising the deformation amount. The dynamic softening behavior is mainly induced by the severe dynamic globularization of lamellar α phases. The globularization of α phase is always accompanied by the formation of high‐angle grain boundaries (HAGBs). The fraction of globularized α phases increases with the increasing deformation temperature. The fracture mechanism is microvoid coalescence, i.e., in the initial stage of tensile deformation, the microvoids begin to emerge. With the increasing deformation amount, the number of microvoids increases, and the microvoids accumulate and accelerate to propagate until the final fracture. According to the experimental flow stress curves, a modified Arrhenius‐type equation and a Hensel–Spittel (HS) model are developed to forecast the flow stresses. The average absolute relative error of the established strain‐compensated Arrhenius‐type (SCAT) and HS models are 6.108% and 3.385%, respectively. Both models can be well used to describe the hot tensile flow characteristics of the Ti–6Al–4V alloy with thick lamellar microstructures.

Unraveling the Effect of Deformation Temperature on the Mechanical Behavior and Transformation‐Induced Plasticity of the SUS304L Stainless Steel

“…The results of WHC revealed that the change in the workhardening rate (WHR) [17][18][19][20][21] with temperature is an important factor in the second category, and hence, the work-hardening behavior was studied and summarized in Figure 2a. In the first category, the usual work-hardening behavior of metallic materials can be seen [16] ; whereas in the second category, there is a tendency to change the decreasing trend of WHR toward a sharp increase and appearance of a peak point in the WHR plot.…”

Constitutive Equations for Describing the Hot Compressed Behavior of TC4–DT Titanium Alloy

“…About Equation (36), α is a function of stain. The values of α can be gained based on the seventh polynomial related to strain, which is shown in Figure 5 a [ 37 ]. Other material parameters can be obtained by multiple linear regression, which is listed in Table 3 .…”

Constitutive Equations for Describing the Warm and Hot Deformation Behavior of 20Cr2Ni4A Alloy Steel

“…Therefore, constants m 7 and m 8 are usually taken as zero. The material parameter α in Equation (9) can be determined by the polynomial in α and strain of the original strain-compensated Arrhenius-type equation [32].…”

“…Moreover, the Hensel-Spittel equation can be used to describe the relationship between strain, strain rates, temperatures and stress based on the 6061 aluminum alloy, the Mg-9Li-3Al-2Sr-2Y alloy, the TiAl-Mo alloys, HSLA350/440 and DP350/600 steels [28][29][30][31]. Moreover, based on the hot tensile deformation of Ti-6Al-4V Alloy, the Hensel-Spittel equation has a higher prediction accuracy than the strain-compensated Arrhenius-type equation [32].…”