Influence of Cr Addition on the HAZ of Austenitic Fe-Mn-Al-C Lightweight Steel Under Various Welding Heat Inputs

This study investigates the effects of chromium addition on phase transformation behavior and mechanical properties in the heat-affected zone (HAZ) of austenitic lightweight steels under various welding heat input conditions. Fe-30.0Mn-10.4Al-0.9C-xCr alloys were fabricated and subjected to simulated welding thermal cycles using a Gleeble simulator with heat inputs ranging from 10 to 300 kJ/cm. Microstructural analyses were conducted via OM, SEM, XRD, and TEM, while Vickers hardness test was conducted to understand κ-carbide precipitation behavior. The results confirmed that the addition of Cr promoted ferrite formation, suppressed austenite grain coarsening in the HAZ, and inhibited κ-carbide precipitation in HAZ regardless of welding heat input. TEM analysis and microhardness measurements also confirmed that Cr effectively suppressed κ-carbide precipitation in the HAZ, and this suppression is attributed to the consumption of κ-carbide forming elements during ferrite stabilization. These findings indicate that Cr addition is an effective approach for enhancing the weldability and mechanical reliability of Fe-Mn-Al-C austenitic lightweight steels, providing valuable insights for the design of advanced structural materials with superior performance.