Abstract
The deformation behavior of a 2024 aluminum alloy sheet at elevated temperatures was studied by uniaxial hot tensile tests over the nominal initial strain rate range of 0.001–0.1 s−1 and temperature range of 375–450 °C. In order to analyze the deformation behavior with higher accuracy, a digital image correlation (DIC) system was applied to determine the strain distribution during hot tensile tests. Local stress-strain curves for different local points on the specimens were calculated. The strain rate evolution of each point during the tensile tests was investigated under different deformation conditions. Then, an improved Fields–Backofen (FB) model, taking into account the local strain rate evolution instead of the fixed strain rate, was proposed to describe the constitutive behaviors. It has been found that obvious non-uniform strain distribution occurred when the true strain was larger than 0.3 during hot tensile tests. The strain rate distribution during deformation was also non-uniform. It showed increasing, steady, and decreasing variation tendencies for different points with the increasing of strain, which led to the local flow stress being different at different local points. The flow stresses predicted by the improved FB model showed good agreement with experimental results when the strain rate evolutions of local points during tensile tests were considered. The prediction accuracy was higher than that of traditional FB models.
Highlights
In recent years, aluminum alloys have been widely used in the aviation and automotive industries, due to their high strength to weight ratio and corrosion resistance [1,2]
The material flow behavior is often complex during hot deformation, which is significantly affected by processing parameters, i.e., the strain, strain rate, and temperature [8,9]
The percentage linear regression with εmax, which indicated that the inhomogeneity of deformation increased with the of uniform deformation area had a linear regression with εmax, which indicated that the proceeding of strain
Summary
Aluminum alloys have been widely used in the aviation and automotive industries, due to their high strength to weight ratio and corrosion resistance [1,2]. Agirre et al [23] further verified the validity of the DIC technique on the measurement of stress-strain curves during inhomogeneous deformation stages by various materials of steels and titanium alloys at room temperature. By using the DIC system, a localized small area, where the strain can be regarded as uniform, is defined at the necking zone to measure the true strain In this way, more accurate flow stress curves at the inhomogeneous deformation stage are achieved at room temperature. Bariani et al [27] used the DIC system to study the deformation behavior of a 6016 aluminum alloy with temperatures ranging from 20 to 500 ◦ C and strain rates ranging from 0.01 to 1 s−1 They take the non-uniform deformation into account, the strain rate was still regarded as a constant during hot tensile tests. Point was used to predict the flow behavior of the material
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