Improving the Low-Temperature Toughness of a High-Strength, Low-Alloy Steel with a Lamellarization Heat Treatment

15-min lamellarization (QL) heat treatment near the A_c3 was applied to a 0.15C–3Ni–1.6Cr–0.5Mo HY-80 steel to increase its low-temperature toughness. The resultant microstructure and mechanical properties were characterized via microscopy, high-energy x-ray diffraction (HEXRD), quasi-static tensile testing, and Charpy impact testing. The results from the QL treatment were compared to a baseline of quench-and-tempered (QT) HY-80. When measured by HEXRD, the QL treatment increased both the volume fraction and lattice parameter of retained austenite, which is indicative of a more film-like austenite phase. This was accompanied by an increase in the low-temperature impact toughness versus the baseline QT condition without a significant decrease in the 0.2