مشخصات پژوهش

This article investigates the strength and ductility properties of a low-alloy steel with a carbon content of 0.32 wt.% after performing one-, two- and three- step austempering processes. Dilatometry tests were used to extract the mandatory data for heat treatment process design, and FE-SEM and XRD were used to evaluate the microstructural characteristics of the heat-treated materials. Quasi-static tensile tests and high strain rate Hopkinson tests were performed to evaluate the strength-ductility combinations. The results showed that step-austempering procedures ended in microstructural features such as nanoscale bainitic ferrites and austenite films in bainitic sheaves separated by austenite microblocks. The size and morphology of the microstructural constituents were comparable to those of ordinary nanos- tructured high-carbon bainitic steels after one-step isothermal bainitic heat treatment. In addition, it was confirmed that a significant improvement in mechanical properties could be achieved by changing the chemical composi- tion. Finally, the strength values obtained at very high strain rates were comparable to those of ordinary nanostructured bainitic steels with high carbon content obtained by a one-step isothermal heat treatment process.