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Dominating Role of Film‐Like Carbon‐Enriched Austenite for the Simultaneous Improvement of Strength and Toughness in Low‐Carbon Steel
Steel Research International ( IF 2.2 ) Pub Date : 2020-08-14 , DOI: 10.1002/srin.202000344
Kai Yang 1, 2 , Wei Ding 1, 2 , Shilong Liu 1, 2 , Wei Li 1, 2 , Xuejun Jin 1, 2
Affiliation  

Multiphase microstructures containing film‐like carbon‐enriched austenite and martensite matrix represent an ideal microstructure that can facilitate the breakthrough of the trade‐off between strength and toughness, as well as good low‐temperature toughness in high‐strength steels. In this study, to determine the impact of film‐like carbon‐enriched austenite on the toughness of low‐carbon high‐strength steel, quenching and low‐temperature partitioning process is applied to a newly designed alloy. The quenching step results in a mixed microstructure consisting of a martensite matrix with high dislocation density and film‐like retained austenite, which is stabilized via carbon enrichment during tempering at 200 ºC for 60 min. Thus, the produced high‐strength steel specimen shows excellent mechanical properties (yield strength = 1201 MPa and tensile strength = 1550 MPa) and superior toughness (68.8 J at −60 ºC). Its strength primarily results from dislocation strengthening, grain boundary strengthening, and solid solution strengthening, and its superior low‐temperature toughness is associated with the film‐like carbon‐enriched austenite, which relaxes local stress, dissipates the plastic energy at the microcrack tip, and delays the initiation and propagation of cracks. Finally, a schematic diagram is designed to elucidate the effect of the retained austenite stabilization on the ductile–brittle transition temperature.

中文翻译:

膜状富碳奥氏体在同时提高低碳钢强度和韧性方面的主导作用

包含薄膜状富碳奥氏体和马氏体基体的多相组织是理想的组织,可以促进强度和韧性之间的折衷突破,以及高强度钢的良好低温韧性。在这项研究中,为了确定膜状富碳奥氏体对低碳高强度钢韧性的影响,将淬火和低温分配工艺应用于新设计的合金。淬火步骤产生了由高位错密度的马氏体基体和薄膜状残留奥氏体组成的混合微观结构,通过在200ºC回火60 min期间进行碳富集化,可以使之稳定。从而,所生产的高强度钢样品显示出优异的机械性能(屈服强度= 1201 MPa,抗拉强度= 1550 MPa)和优异的韧性(在60ºC时为68.8 J)。它的强度主要来自位错强化,晶界强化和固溶强化,其优异的低温韧性与薄膜状富碳奥氏体有关,后者可缓和局部应力,耗散微裂纹尖端的塑性能,并延迟了裂纹的产生和传播。最后,设计了一个示意图以阐明残余奥氏体稳定对延性-脆性转变温度的影响。固溶强化,其优异的低温韧性与薄膜状富碳奥氏体有关,后者可缓和局部应力,耗散微裂纹尖端的塑性能,并延缓裂纹的产生和传播。最后,设计了一个示意图以阐明残余奥氏体稳定对延性-脆性转变温度的影响。固溶强化,其优异的低温韧性与薄膜状富碳奥氏体有关,后者可缓和局部应力,耗散微裂纹尖端的塑性能,并延缓裂纹的产生和传播。最后,设计了一个示意图以阐明残余奥氏体稳定对延性-脆性转变温度的影响。
更新日期:2020-08-14
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