Role of surrounding phases on deformation-induced martensitic transformation of retained austenite in multi-phase TRIP steel
Role of surrounding phases on deformation-induced martensitic transformation of retained austenite in multi-phase TRIP steel
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DOI：
10.1016/j.msea.2023.145089
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
Lavakumar Avala;Myeong-heom Park;Sukyoung Hwang;H. Adachi;Masugu Sato;R. Ray;M. Murayama;N. Tsuji
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文献类型：
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作者：
Lavakumar Avala;Myeong-heom Park;Sukyoung Hwang;H. Adachi;Masugu Sato;R. Ray;M. Murayama;N. Tsuji
变形诱发马氏体相变是低合金多相钢获得高强度和大塑性的关键现象。变形过程中由软奥氏体向硬马氏体相变，即相变诱发塑性（TRIP）效应，显著增强了合金的应变硬化能力。TRIP效应的发生可由奥氏体的碳含量、晶粒尺寸和形貌等特征控制。此外，变形过程中与奥氏体晶粒周围其他相的力学相互作用会影响奥氏体的稳定性，这一点尚未得到澄清。目前的研究已经阐明了周围相如何影响奥氏体抵抗变形诱发马氏体转变的机械稳定性。在Fe-1.6Mn-1.4Si-1.0Ni-0.5Al-0.2C中形成了由铁素体(α) +奥氏体(γ) +马氏体(M)三种不同相组成的两种多相组织和铁素体(α) +奥氏体（γ）两种不同相组成的多相组织，保留的奥氏体特征基本保持不变。结果表明，与α+γ试样相比，α+γ+M试样在拉伸变形过程中变形诱发马氏体转变的速率较慢，表明α+γ+M试样具有较高的奥氏体稳定性。拉伸变形过程中的原位同步x射线衍射测量结果表明，奥氏体与相邻相（铁素体、马氏体和变形诱发马氏体）之间存在明显的应力分配，影响了奥氏体向变形诱发马氏体的相变速率。此外，原位同步x射线衍射分析还表明，由于马氏体转化过程中引入的奥氏体位错密度较高，导致α+γ+M试样中的奥氏体始终比α+γ试样中的奥氏体具有更高的应力，因此在拉伸变形过程中，α+γ+M试样的变形诱发马氏体转变所需的应力高于α+γ试样。
Deformation-induced martensitic transformation is a key phenomenon to manage both high strength and large ductility in low alloy multi-phase steels. Significant enhancement of strain hardening ability could be achieved by the phase transformation from soft austenite to hard martensite during deformation, which is known as transformation induced plasticity (TRIP) effect. The occurrence of TRIP effect can be controlled by austenite characteristics like carbon content, grain size and morphology. Additionally, the mechanical interaction with other phases surrounding each austenite grain during deformation would affect the stability of austenite, which has not been clarified. The current study has clarified how surrounding phases affect the mechanical stability of austenite against deformation-induced martensitic transformation. Two types of multi-phase microstructures composed of three different phases, i.e., ferrite (α) + austenite (γ) + martensite (M) and two phases of ferrite (α) + austenite (γ) were fabricated in Fe-1.6Mn-1.4Si-1.0Ni-0.5Al-0.2C, maintaining the characteristics of retained austenite nearly the same. It was found that the α+γ+M specimen exhibited slower rate of deformation-induced martensitic transformation during tensile deformation than the α+γ specimen, indicating higher austenite stability in the α+γ+M specimen. Thein-situsynchrotron XRD measurements during tensile deformation revealed that there was significant stress partitioning between austenite and adjacent phases (ferrite, martensite and deformation-induced martensite), which influenced the phase transformation rate of austenite into deformation-induced martensite. Furthermore, it was also clarified by thein-situsynchrotron XRD that the austenite in the α+γ+M specimen always had higher stress than that in the α+γ specimen due to higher dislocation density in austenite introduced by martensitic transformation to form pre-existing martensite, so that higher stress was required for deformation-induced martensitic transformation in the α+γ+M specimen during tensile deformation than the α+γ specimen.