Sugimoto Koh-Ichi, Shioiri Shoya, Kobayashi Junya
Graduate School of Science and Technology, Shinshu University, Nagano 380-8553, Japan.
Graduate School of Science and Engineering, Ibaraki University, Hitachi 316-8511, Japan.
Materials (Basel). 2024 Jul 18;17(14):3554. doi: 10.3390/ma17143554.
The effects of mean normal stress on the deformation properties such as the strain-hardening, strain-induced martensite transformation, and micro-void initiation behaviors of low-carbon ultrahigh-strength TRIP-aided bainitic ferrite (TBF), bainitic ferrite/martensite (TBM), and martensite (TM) steels were investigated to evaluate the various cold formabilities. In addition, the deformation properties were related to the microstructural properties such as the matrix structure, retained austenite characteristics, and second-phase properties. Positive mean normal stress considerably promoted strain-induced martensite transformation and micro-void initiation, with an increased strain-hardening rate in an early strain range in all steels. In TM steel, the primary martensite matrix structure suppressed the micro-void initiation through high uniformity of a primary martensite matrix structure and a low strength ratio, although the strain-induced transformation was promoted, and a large amount of martensite/austenite constituent or phase was contained. A mixed matrix structure of bainitic ferrite/primary martensite in TBM steel also suppressed the micro-void initiation because of the refined microstructure and relatively stable retained austenite. Promoted micro-void initiation of TBF steel was mainly promoted by a high strength ratio.
研究了平均正应力对低碳超高强度相变诱发塑性贝氏体铁素体（TBF）钢、贝氏体铁素体/马氏体（TBM）钢和马氏体（TM）钢的应变硬化、应变诱发马氏体转变和微孔萌生行为等变形性能的影响，以评估各种冷成型性。此外，变形性能还与基体结构、残余奥氏体特征和第二相性能等微观结构性能相关。正平均正应力显著促进了应变诱发马氏体转变和微孔萌生，所有钢种在早期应变范围内的应变硬化率均有所提高。在TM钢中，尽管促进了应变诱发转变且含有大量马氏体/奥氏体组织或相，但初生马氏体基体结构通过初生马氏体基体结构的高均匀性和低强度比抑制了微孔萌生。TBM钢中贝氏体铁素体/初生马氏体的混合基体结构也抑制了微孔萌生，这是由于其细化的微观结构和相对稳定的残余奥氏体。TBF钢中微孔萌生的促进主要是由高强度比引起的。
