Stabilization of retained austenite by the two-step intercritical heat treatment and its effect on the toughness of a low alloyed steel
Stabilization of retained austenite by the two-step intercritical heat treatment and its effect on the toughness of a low alloyed steel
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DOI：
10.1016/j.matdes.2014.02.035
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发表时间：
2014-07
影响因子：
8.4
通讯作者：
Z. Xie;S. Yuan;Wenhao Zhou;J. Yang;Hui Guo;C. Shang
中科院分区：
文献类型：
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作者：
Z. Xie;S. Yuan;Wenhao Zhou;J. Yang;Hui Guo;C. Shang
在重量% （wt.%）的Fe-0.08C-0.5Si-2.4Mn-0.5Ni钢中，通过两步临界间热处理获得了细小的膜状稳定残余奥氏体。临界间退火的第一步是形成初步富合金马氏体和贫合金临界间铁素体的混合组织，分别称为“还原组织”和“未还原组织”。第二步临界间回火有利于沿回火组织生成膜状稳定的回火奥氏体。采用扫描电镜（SEM）、透射电镜（TEM）、膨胀仪（dilatometry）和x射线衍射仪（XRD）对残余奥氏体的稳定性进行了研究。C、Mn和Ni的临界间分配导致的两步奥氏体还原转变被认为是两步临界间热处理过程中残余奥氏体稳定的潜在基础。稳定的残余奥氏体不仅有利于提高塑性，而且通过限制脆性断裂提高低温韧性。当钢中残留10%（体积分数）的奥氏体时，可获得较高的低温韧性，在- 80℃时平均夏比冲击能为65 J。
Fine film-like stable retained austenite was obtained in a Fe–0.08C–0.5Si–2.4Mn–0.5Ni in weight percent (wt.%) steel by the two-step intercritical heat treatment. The first step of intercritical annealing creates a mixed microstructure of preliminary alloy-enriched martensite and lean alloyed intercritical ferrite, which is called as “reverted structure” and “un-reverted structure”, respectively. The second step of intercritical tempering is beneficial for producing film-like stable reverted austenite along the reverted structure. The stabilization of retained austenite was studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), dilatometry and X-ray diffraction (XRD) analysis. The two-step austenite reverted transformation associated with intercritical partition of C, Mn and Ni is believed to be the underlying basis for stabilization of retained austenite during the two-step intercritical heat treatment. Stable retained austenite is not only beneficial for high ductility, but also for low temperature toughness by restricting brittle fracture. With 10% (volume fraction) of retained austenite in the steel, high low temperature toughness with average Charpy impact energy of 65 J at −80 °C was obtained.