Temperature effect on adiabatic shear phenomenon and microstructure evolution of directional energy deposition 316 L stainless steel

Abstract

Considering that the effect of temperature on the microstructural evolution and mechanical behavior of directed energy deposited (DED) 316 L stainless steel under high strain rates remains unclear, this study analyzes the macro/micro deformation behavior of DED-316 L under different temperatures and strain rates. It was observed that at 5000 s⁻¹ and 20 °C, adiabatic shear bands formed, whereas when the temperature increased to 400 °C, the adiabatic shear bands transformed into deformation bands. Moreover, the increase in temperature led to a 67.07 % reduction in geometrically necessary dislocation density. At a strain rate of 4000 s⁻¹, the effect of temperature on the twin percentage after material deformation was analyzed using Transmission Electron Microscopy. At 20 °C, the twin volume fraction was 35 %, while at 400 °C, the increased temperature raised the critical stress for twinning, and the twin percentage decreased to 9 %, a reduction of 74.29 %. A constitutive equation based on dislocation density evolution behavior was established to predict the stress-strain curve changes under high strain rates and high-temperature conditions. By comparing the predicted average geometrically necessary dislocation density with the experimentally obtained stress-strain curve, a Pearson correlation coefficient of 0.96 was obtained, confirming the accuracy of the model. This study provides important insights into the relationship between the macro/microstructural evolution and mechanical behavior of DED-316 L under dynamic loading conditions.