Abstract The initial formation of athermal martensite was proven to accelerate the subsequent bainite formation kinetics during isothermal holdings below the martensite-start temperature (Ms). The presence of prior athermal martensite (PAM) within the phase mixture is expected to modify the overall mechanical response of these newly-designed multiphase steels. Differences stem not only from the balance of product phases, but also from the effect of tempering of the PAM with variations in the applied holding time. This work investigates the effect of tempering time on the mechanical behaviour of the PAM and, as consequence, on the overall mechanical response of these microstructures. Results show that, for short holding times (several minutes), PAM yields similar to as-quenched martensite while, for longer holding times, its yielding behaviour becomes comparable to the one exhibited by typical tempered martensite. Furthermore, the use of Kocks-Mecking curves for the analysis of the mechanical performance confirms the bainitic character of the product phase isothermally formed below Ms. Tailoring the bainitic-martensitic microstructure with variations of the holding time below Ms enables to obtain advanced multiphase steels with comparable mechanical properties to those exhibited by conventional bainitic steels, but in shorter processing times due to the acceleration of bainite formation.

中文翻译：

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揭示在 M 以下等温获得的高级多相钢的机械性能

摘要 无热马氏体的初始形成已被证明在低于马氏体起始温度 (Ms) 的等温保持期间加速了随后的贝氏体形成动力学。相混合物中原有无热马氏体 (PAM) 的存在有望改变这些新设计的多相钢的整体机械响应。差异不仅源于产品相的平衡，还源于 PAM 回火的影响以及应用保温时间的变化。这项工作研究了回火时间对 PAM 机械行为的影响，进而对这些微观结构的整体机械响应的影响。结果表明，对于较短的保温时间（几分钟），PAM 的产量类似于淬火马氏体，而对于较长的保温时间，它的屈服行为变得可与典型回火马氏体表现出的行为相媲美。此外，使用 Kocks-Mecking 曲线分析机械性能证实了在 Ms 下等温形成的产物相的贝氏体特征。调整贝氏体-马氏体显微组织并在 Ms 以下保持时间变化，可以获得具有以下特性的高级多相钢与传统贝氏体钢表现出的机械性能相当，但由于贝氏体形成加速，加工时间更短。