Abstract The effects of Si concentration and austenite grain size (AGS) on the tensile properties, stacking fault energy (γ), and deformation mode of Fe-18Mn-0.6C (wt.%) steel were investigated to improve the yield strength (YS) of twinning-induced plasticity (TWIP) steel. The 3% Si-added steel revealed the higher YS than previous TWIP steels at the same level of AGS. In particular when the AGS was ∼6.8 μm, its YS reached ∼593 MPa, which is comparable to the YS (613 MPa) of transformation-induced plasticity steel with a tensile strength of 980 MPa. The measured γ of 3% Si-added steel was exponentially decreased with grain coarsening primarily due to the reduction of micro-strain, finally reaching its intrinsic γ (γint) at the AGSs above ∼70 μm. This indicates that the γint measurement by means of X-ray diffractometry must be performed using coarse-grained specimens with the AGSs above ∼70 μm. Critical resolved shear stresses for twinning (τtwin) and e-martensitic transformation (τe-mart) were evaluated as a function of AGS in (0-3%) Si-added steels. Whereas the τtwin value was slightly decreased with increasing AGS or Si concentration, the τe-mart value was more significantly reduced. This indicates that e-martensitic transformation precedes mechanical twinning with increasing AGS or Si concentration. As a result, a transition of deformation mode from mechanical twinning to e-martensitic transformation occurred with grain coarsening in Si-added steels. A critical AGS for the transition of deformation mode was reduced from ∼69 μm to ∼15 μm with increasing Si concentration from 0.5 wt.% to 3.0 wt.%.

中文翻译：

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加硅Fe-18Mn-0.6C钢的拉伸性能及变形方式

摘要 研究了 Si 浓度和奥氏体晶粒尺寸 (AGS) 对 Fe-18Mn-0.6C (wt.%) 钢的拉伸性能、层错能 (γ) 和变形模式的影响，以提高屈服强度 (YS)。 ) 的孪生诱导塑性 (TWIP) 钢。在相同的 AGS 水平下，添加 3% Si 的钢显示出比以前的 TWIP 钢更高的 YS。特别是当 AGS 为~6.8 μm 时，其 YS 达到~593 MPa，与抗拉强度为 980 MPa 的相变诱导塑性钢的 YS (613 MPa) 相当。添加 3% Si 的钢的测量 γ 随晶粒粗化呈指数下降，这主要是由于微应变的减少，最终在 AGS 大于 70 μm 处达到其本征 γ (γint)。这表明通过 X 射线衍射法进行的 γint 测量必须使用 AGS 大于 70 μm 的粗晶试样进行。孪生 (τtwin) 和电子马氏体相变 (τe-mart) 的临界分辨剪切应力被评估为 (0-3%) 添加硅钢中 AGS 的函数。随着 AGS 或 Si 浓度的增加，τtwin 值略有下降，而 τe-mart 值下降得更显着。这表明随着 AGS 或 Si 浓度的增加，e-马氏体转变先于机械孪晶。结果，随着Si添加钢中的晶粒粗化，变形模式从机械孪晶转变为e-马氏体转变。随着Si浓度从0.5wt％增加，变形模式转变的临界AGS从~69μm降低到~15μm。