The present study investigated the microstructure evolution and strain hardening of two types of high-Mn austenitic steels, i.e., Fe−18.5Mn–7Cr−0.6C(00N) and Fe−18.5Mn–7Cr−0.6C−0.21N(21N), during tensile deformation. The results revealed that the addition of N increased the yield and tensile strength of high-Mn austenitic steel with almost no loss of elongation. The strain hardening of the 00N and 21N steels was closely related to the microstructure evolution. At the initial tensile deformation stage, dislocation slip was the dominant deformation mechanism of the two test steels. Due to the addition of N, the dislocation cross-slip in the 21N steel was suppressed, leading to a higher strain hardening rate. With the increase of true strain, the mechanical twins became active. At a true strain of 0.18, a unique network structure of mechanical twins and dislocation cells was formed in the 00N steel, and the thickness and spacing of mechanical twins were lower, which increased the resistance of dislocation motion and made its strain hardening rate slightly higher than that of the 21N steel. However, at a true strain of 0.37, the thickness and spacing of mechanical twins in the 21N steel decreased rapidly, which increased the difficulty of dislocation movement, resulting in a higher strain hardening rate than that of the 00N steel. In short, the increased resistance of dislocation motion was the fundamental reason for the enhanced strain hardening rate, rather than mechanical twins.

中文翻译：

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N对高锰奥氏体钢拉伸变形过程中组织演变和应变硬化的影响

本研究研究了两种高锰奥氏体钢 Fe−18.5Mn–7Cr−0.6C(00N) 和 Fe−18.5Mn–7Cr−0.6C−0.21N(21N) 的显微组织演变和应变硬化，在拉伸变形过程中。结果表明，添加N提高了高锰奥氏体钢的屈服强度和抗拉强度，而延伸率几乎没有损失。00N和21N钢的应变硬化与显微组织的演变密切相关。在初始拉伸变形阶段，位错滑移是两种试验钢的主要变形机制。由于N的添加，21N钢中的位错交叉滑移被抑制，从而导致更高的应变硬化率。随着真实应变的增加，机械孪生变得活跃。在真应变为0.18时，00N钢中形成了独特的机械孪晶和位错单元的网络结构，且机械孪晶的厚度和间距较小，增加了位错运动的阻力，使其应变硬化率略高高于21N钢。然而，在真应变为0.37时，21N钢中机械孪晶的厚度和间距迅速减小，增加了位错运动的难度，导致应变硬化率高于00N钢。总之，位错运动阻力的增加是应变硬化率增强的根本原因，而不是机械孪晶。