The influence of austenitizing temperature and austenite grain size on the crystallographic characteristics and mechanical properties of transformation products was investigated in a low-alloy steel. Annealing at a lower temperature after austenitization at 1050 °C can reduce the vacancy concentration and enhance the stability of austenite, thereby determining the martensite-start (M_s) temperature and density of twin-related V1/V2 variant pairs. V1/V2 variant pairs are predominately generated by autocatalytic nucleation, which can promote transformation by self-accommodation. Annealing at 800 °C after austenitization at 1050 °C generated the highest content of V1/V2 variant pairs, which contributed to high values of strength, Charpy impact energy, and elongation. In addition to refining the austenite grain size, niobium (Nb) microalloying increases the packet boundaries of the transformation products, mainly because the refined austenite grains provide more nucleation sites for the martensitic transformation. However, the density of block boundaries decreases after austenite refinement by Nb microalloying, owing to insufficient autocatalytic nucleation.

在低合金钢中研究了奥氏体化温度和奥氏体晶粒尺寸对相变产物晶体学特征和力学性能的影响。1050℃奥氏体化后低温退火可降低空位浓度，增强奥氏体稳定性，从而确定马氏体起始点（M _s) 双胞胎相关 V1/V2 变体对的温度和密度。V1/V2 变体对主要由自催化成核生成，可通过自我调节促进转化。在 1050 °C 奥氏体化后在 800 °C 退火产生最高含量的 V1/V2 变体对，这有助于获得高值的强度、夏比冲击能量和伸长率。除了细化奥氏体晶粒尺寸外，铌 (Nb) 微合金化还增加了相变产物的包边界，主要是因为细化的奥氏体晶粒为马氏体相变提供了更多的形核位点。然而，由于自催化成核不足，在通过 Nb 微合金化细化奥氏体后，块边界的密度降低。