Medium-manganese steel that undergoes Lüders deformation exhibits good uniform elongation owing to large elongation with a yield plateau. To accurately predict the deformation behavior in engineering applications, the yield stresses of medium-manganese steel (5% Mn), exhibiting the transformation-induced plasticity (TRIP) effect were investigated during elongation under a multi-axial stress state (MSS). Compact tensile tests with real-time diameter measurements were conducted on smooth and notched, tiny round-bar specimens to evaluate the local yield stress and strain without the Lüders band propagation effect. Consequently, the true stress plateau was measured without the upper yield point for the smooth round-bar specimen, and the cross-sectional average true stress of the blunt notched round-bar specimens had the same plateau as the smooth round-bar specimen. The sharp-notched round-bar specimen exhibited a two-stage linear increase in true stress. The true stresses of the three specimens at the initial yield point were almost identical. Under the MSS, the hydrostatic stress typically increases the true stress at the initial yield point. The independence of the MSS indicates that the yield stress during elongation was independent of the shear-dominant crystal slip resistance. Finite element (FE) analysis using the Mises yield locus did not express the true stress plateau and its independence of the MSS. Additionally, the transformation rate of retained austenite was measured for mechanistic analysis; however, the TRIP effect did not contribute to this unusual independence because it started at the intermediate yield elongation stage. Thus, the stress criterion for the generation of mobile dislocations can determine yield stress.

经历吕德斯变形的中锰钢由于具有屈服平台的大伸长率而表现出良好的均匀伸长率。为了准确预测工程应用中的变形行为，对具有相变诱导塑性 (TRIP) 效应的中锰钢 (5% Mn) 在多轴应力状态 (MSS) 伸长过程中的屈服应力进行了研究。对光滑和有缺口的微小圆棒样品进行了具有实时直径测量的紧凑拉伸试验，以评估没有吕德斯带传播效应的局部屈服应力和应变。因此，在没有上屈服点的情况下测量了光滑圆棒样品的真实应力平台，并且钝缺口圆棒样品的横截面平均真应力具有与光滑圆棒样品相同的平台。尖缺口圆棒样品的真应力呈现两阶段线性增加。三个样品在初始屈服点的真实应力几乎相同。在 MSS 下，静水应力通常会增加初始屈服点处的真实应力。MSS 的独立性表明伸长过程中的屈服应力与剪切主导的晶体滑移阻力无关。使用 Mises 屈服轨迹的有限元 (FE) 分析并未表达真实的应力平台及其与 MSS 的独立性。另外，还测量了残余奥氏体的转变率以进行力学分析；然而，TRIP 效应并没有促成这种不寻常的独立性，因为它是在中间屈服伸长阶段开始的。因此，产生移动位错的应力标准可以确定屈服应力。