Comparison of dynamic compressive flow behavior of mild and medium steels over wide temperature range

Abstract

This article uses the compressive split-Hopkinson pressure bar to compare the dynamic flow behaviors of S15C mild steel and S50C medium alloy heat-treatable steel (abbreviated hereafter to medium steel) at temperatures ranging from 25 °C to 800 °C. The effects of carbon content, strain rate, and temperature on the mechanical responses of the two metals are evaluated. The microstructures of both steels are studied using a transmission electron microscopy (TEM) technique. The flow stress of both carbon steels is found to increase with strain rate, but to decrease with temperature. Furthermore, the deformation resistance and the work-hardening rate both increase with increasing carbon content. The activation energy, ⌬G*, of the two metals varies as a function of the strain rate and temperature, but is virtually unaffected by the carbon content. The present study identifies a maximum ⌬G* value of 58 kJ/mol for the S15C mild steel and 54.9 kJ/mol for the S50C medium steel. A Zerilli-Armstrong bcc constitutive model using appropriate coefficients is applied to describe the high-strain-rate plastic behaviors of the S15C and S50C carbon steels. The errors between the calculated stress and the measured stress are found to be less than 5 pct. Transmission electron microscopy microstructural observations reveal that the dislocation density and the degree of dislocation tangling increase with increasing strain rate in both steels. Additionally, the TEM observations indicate that a higher strain rate reduces the size of the dislocation cells. Furthermore, it is shown that the annihilation of dislocations occurs more readily at elevated temperatures. The current results provide a valuable reference for the application of S15C mild steel and S50C medium steel in high-speed plastic forming processes.

Impact Response and Microstructural Evolution of Biomedical Titanium Alloy under Various Temperatures

“…The temperature effect can be quantified via a temperature-sensitivity parameter, b a , defined as |(r 2 -r 1 )/(T 2 -T 1 )|. [33,34] Figure 6(b) shows the correlation between the temperature sensitivity of the Ti alloy and the temperature as a function of the strain and strain rate. It can be seen that the highest temperature sensitivity occurs at 500°C, while the lowest occurs at 700°C.…”

Effects of strain rate and temperature on mechanical behaviour of Ti–15Mo–5Zr–3Al alloy

“…Note that for the majority of metals, dislocation movement occurs more readily as the temperature increases, and hence the deformation resistance of the material decreases. Thus, the formulation [(σ 2 − σ 1 )/(T 2 − T 1 )] can be used to quantify the relative reduction in the material strength caused by a specified increase in the deformation temperature under constant strain and strain rate conditions (Morrone, 1986;Lee and Liu, 2005). Fig.…”

A thermo-viscoplastic constitutive model to predict elevated-temperature flow behaviour in a titanium-modified austenitic stainless steel

“…The Original JC model has been extensively used as it requires less number of experimental data for evaluation of the materials constants. On the other hand, the ZA model has been used for different fcc and bcc materials over different strain rates at temperatures between room temperature and 0.6T m [23][24][25][26]. ZA model is preferred to JC model as it couples the effects of strain rate and temperature [27][28][29] , it is particularly not suitable for prediction of flow stress at temperatures above 0.6T m and at lower strain rates [30].…”