2026 Taylor Heating Rate Austenitisation

Coarse prior austenite grain (PAG) structures in high-strength steels often result in poor mechanical performance, particularly in parts produced by wire-arc additive manufacturing (WAAM). This study investigates the effect of heating rate during austenitisation on grain refinement in two steels—a low-alloy steel (300 M) and a maraging steel (Custom 465/C210), both exhibiting coarse columnar PAGs in their as-WAAM'd state. Through high-temperature in-situ electron backscatter diffraction, we observed the austenite 'memory effect', where the columnar structure is retained before occasionally leading to autogenous recrystallisation. Notably, in 300 M, transitioning from a continuous to a discontinuous recrystallisation mechanism was influenced by decreasing heating rates, with further reductions suppressing recrystallisation and leaving only the memory effect. In contrast, Custom 465/C210 underwent significant PAG refinement across all heating rates, though crystallographic texture was still inherited from the original columnar PAGs and twins in the as-built material. These findings provide valuable insights into strategies for grain refinement in steels with coarse PAGs, emphasizing the critical role of controlled heating rates in industrial processing.