The deformation behaviour of materials at the micro-scale level is different from that at the macro-scale level due to the effect of grain size (GS). The mechanism of the influence on martensitic transformation by GS is still unclear, and there are relatively few studies on the relationship between grain refinement and martensitic transformation, most of which focus on the relationship between the initial GS of the material and martensitic transformation. Therefore, in this study, the interaction between grain refinement and martensitic transformation was investigated using a dislocation density-based multiscale constitutive model that incorporated dislocation sliding, strain-induced martensitic transformation (SIMT) related to grain size, and grain refinement. The proposed model evaluated the GS-dependent deformation behaviour of 316L stainless steel (SS). Subsequently, a genetic algorithm was used to determine the parameters of the established model, and the calculated results were compared with that of the experimental data to verify the accuracy of the model. The developed multiscale constitutive model was implemented in Abaqus user subroutine to further investigate the deformation mechanism and validate its accuracy. The results demonstrated that the GS had a significant effect on the SIMT, with the volume fraction of martensite increasing with a rise in the initial austenite GS. In addition, grain refinement affected SIMT and the growth rate of martensite content decreased with the grain refinement caused by deformation. The formation of martensite led to grain refinement, with the refined grains producing negative feedback on the SIMT, thus inhibiting the occurrence of martensitic transformation. This study revealed the microscopic deformation mechanism of 316L SS and provided a constitutive model for micro-forming.

Graphical Abstract

中文翻译：

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结合晶粒细化和马氏体转变的尺寸相关本构模型

由于晶粒尺寸 (GS) 的影响，材料在微观层面的变形行为不同于宏观层面的变形行为。GS对马氏体相变影响的机理尚不清楚，关于晶粒细化与马氏体相变关系的研究相对较少，大多集中在材料初始GS与马氏体相变的关系上。因此，在本研究中，使用基于位错密度的多尺度本构模型研究了晶粒细化与马氏体相变之间的相互作用，该模型结合了位错滑动、与晶粒尺寸相关的应变诱导马氏体相变 (SIMT) 和晶粒细化。所提出的模型评估了 316L 不锈钢 (SS) 的 GS 相关变形行为。随后，利用遗传算法确定所建立模型的参数，并将计算结果与实验数据进行比较，验证模型的准确性。开发的多尺度本构模型在 Abaqus 用户子程序中实现，以进一步研究变形机制并验证其准确性。结果表明，GS 对 SIMT 有显着影响，马氏体的体积分数随着初始奥氏体 GS 的增加而增加。此外，晶粒细化影响SIMT，马氏体含量的增长速度随着变形引起的晶粒细化而降低。马氏体的形成导致晶粒细化，细化晶粒对 SIMT 产生负反馈，从而抑制马氏体相变的发生。本研究揭示了 316L SS 的微观变形机制，并为微成形提供了本构模型。

图形概要