Deformation Behavior and Plastic Instability of Ultra-High Strength Low Alloy Steel over Wide Temperature and Velocity Range

Ultra-high strength low alloy (UHSLA) steels are one of pivotal materials used in industrial sector. Its diversified compositions and characteristic mechanical properties as per service requirement have created an inevitable place for this steel class. The current study has been carried out on the deformation behavior and plastic instability of newly developed (UHSLA steel) XF1700 over a wide temperature range T-r to near T-m (298-1673 K) and at quasi-static (0.01-1/s) as well as dynamic (10-10(4)/s) conditions. Such a wide range of data were obtained by utilizing chemical composition of this alloy system in JMatPro (an efficient software based on CALPHAD module). The effect of temperature with increasing strain and strain rate has been quantified in terms of a four-parameter exponential model based on two Z (Zener-Hollomon) parameters Z(m) and Z(n), as such to predict cold, warm and hot deformation mechanism by a subsection method. The novelty of this work lies in its simple mathematical model that can describe the deformation behavior of a material for temperature range T-r to near T-m, considering the temperature compensated strain and strain rate factors. EBSD analysis was carried out for microstructural analysis to support the deformation behavior and plastic instability mechanism. Based on four-parameter exponential model, the deformation stability criteria have also been elucidated for all the three zones: Zone I, cold forming zone (298-673 K); Zone II, warm forming zone (673 < T = 973 K) and Zone III, hot forming zone (973 < T 5= 1673 K). Through non-linear regression model in SPSS software, material parameters describing deformation behavior and plastic instability were segregated in parts and the four-parameter exponential model has been verified which is found to be in excellent agreement with available data. The AARE obtained was 2.03% (zone I), 7.17% (zone II) and 4.07% (zone III), respectively, while the overall AARE was 4.42%.

Automated summary

This study investigates the deformation behavior and plastic instability of the newly developed ultra-high strength low alloy steel XF1700 over a wide temperature range and different strain rates. By using the chemical composition of the alloy system in JMatPro software, a four-parameter exponential model is established to predict the deformation mechanism at different temperature zones. EBSD analysis is conducted for microstructural analysis. The material parameters describing deformation behavior and plastic instability are obtained through a nonlinear regression model, and the four-parameter exponential model is found to be in excellent agreement with the experimental data. The overall average absolute relative error (AARE) is 4.42%.