Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb（质量分数,%）钢通过淬火-碳分配-回火（Q-P-T）工艺抗拉强度可达1250 MPa以上兼具良好塑性（大于17%）,显微组织为位错型板条马氏体、微合金碳化物和薄片状残留奥氏体。通过低温拉伸试验分析了Q-P-T钢在-85～25℃下的力学性能并采用透射电镜观察了试样在25℃和-85℃时拉伸前后的显微组织。结果表明,Q-P-T钢在-70～25℃时显示了良好的低温力学性能,仅当拉伸温度低于-70℃时试样塑性开始出现大幅下降;残留奥氏体在未变形前具有良好的低温稳定性,但在变形过程中会发生马氏体相变,产生相变诱发塑性（TRIP）效应,这是Q-P-T钢具有高强度和良好塑性的主要原因。
Fe-0. 25C-1. 5Mn-1.2Si-1.5Ni-0. 05Nb （mass fraction, % ） steel subjected to a novel heat treatment process designated as quenching-partitioning-tempering （Q-P-T） process exhibits high strength （over 1250 MPa） and substantial ductility （elongation over 17% ）,for which the microstructure consists of lath martensite, dispersive distributed carbides and thin film-like retained austenite. The mechanical properties of this Q-P-T steel at - 85-25 ℃ were investigated by tensile tests, and the microstructure of the samples before and after tensile tests at 25 ℃ and - 85 ℃ were characterized by transmission electron microscopy （TEM） , respectively. The results show that Q-P-T steel possesses excellent mechanical properties at - 70 ℃to 25℃ , while the elongation decreases obviously when the temperature drops below -70℃. The microstructure characterization indicates that retained austenite, as the soft phase in Q-P-T steels, presents good stability at low temperatures before plastic deformation. However, it will transform into martensite during plastic deformation, showing the transformation induced plasticity （TRIP） effect, which has been considered as the crucial role on the excellent combination of strength and ductility.
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