Control of Core-shell Type Second Phase Formed via Interrupted Quenching and Intercritical Annealing in a Medium Manganese Steel
Control of Core-shell Type Second Phase Formed via Interrupted Quenching and Intercritical Annealing in a Medium Manganese Steel
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DOI：
10.2355/isijinternational.isijint-2020-164
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发表时间：
2020-12
影响因子：
1.8
通讯作者：
T. Tsuchiyama;T. Sakamoto;Shohei Tanaka;T. Masumura
中科院分区：
文献类型：
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作者：
T. Tsuchiyama;T. Sakamoto;Shohei Tanaka;T. Masumura
中锰钢(Fe-5.0%Mn-1.2%Si-0.10%C合金)从奥氏体单相区间断淬火至M-S至Mf之间的温度，然后在923K的铁素体-奥氏体双相区进行亚温退火，形成了由新鲜的马氏体核和膜状残余奥氏体壳组成的核壳型第二相。通过DICTRA模拟和透射电子显微镜观察，分析了断续淬火试件的回复机理和动力学。关于核壳型第二相对力学性能的影响，推测新鲜马氏体核起到了与DP钢类似的硬性第二相的作用，并通过应力分配强化了加工硬化，而膜状残余奥氏体相由于TRIP效应而有助于提高塑性。随着间歇淬火温度的降低，新生马氏体核的体积分数降低，残余奥氏体壳的稳定性增加。这为控制中锰钢的强塑性平衡提供了可能。从硬质马氏体界面处的应力应变松弛的角度讨论了核壳型第二相对韧性断裂行为的可能有利影响。
Medium manganese steel (Fe-5.0%Mn-1.2%Si-0.10%C alloy) was subjected to interrupted quenching from the austenite single-phase region to a temperature between M s and M f followed by intercritical annealing in the ferrite and austenite dual-phase region at 923 K. As a result, a core-shell type second phase, which consisted of a fresh martensite core surrounded by a film-like retained austenite shell, was formed. The mechanism and kinetics of reversion for the interrupted-quenched specimens were analyzed with DICTRA simulation and TEM observation. With regard to the effect of the core-shell type second phase on mechanical properties, it was inferred that the fresh martensite core functioned as a hard second phase and enhanced work hardening by stress partitioning similar to DP steel, while the film-like retained austenite contributed to improved ductility due to the TRIP effect. As the interrupted quenching temperature decreased, the volume fraction of the fresh martensite core decreased, while the stability of the retained austenite shell increased. This showed potential for controlling the strength and ductility balance of medium manganese steel. A possible beneficial effect of the core-shell type second phase on the ductile fracture behavior was also discussed in terms of stress/strain relaxation at the interfaces between hard martensite and ferrite matrix.