Low-carbon advanced nanostructured steels : microstructure, mechanical properties, and applications

Abstract

Low-carbon advanced nanostructured steels have been developed for various structural engineering applications, including bridges, automobiles, and other strength-critical applications such as the reactor pressure vessels in nuclear power stations. The mechanical performances and applications of these steels are strongly dependent on their microstructural features. By controlling the size, number density, distribution, and types of precipitates, it is possible to produce nanostructured steels with a tensile strength reaching as high as 2 GPa while keeping a decent tensile elongation above 10% and a reduction of area as high as 40%. Besides, through a careful control of strength contributions from multiple strengthening mechanisms, the nanostructured steels with superior strengths and low-temperature impact toughness can be obtained by avoiding the temper embrittlement regime. With appropriate Mn additions, these nanostructured steels can achieve a triple enhancement in ductility (total tensile elongation, TE of ~30%) at no expense of strengths (yield strength, YS of ~1100 to 1300 MPa, ultimate tensile strength, UTS of ~1300 to 1400 MPa). More importantly, these steels demonstrate good fabricability and weldability. In this paper, the microstructure-property relationships of these advanced nanostructured steels are comprehensively reviewed. In addition, the current limitations and future development of these nanostructured steels are carefully discussed and outlined. 新型低碳纳米钢已被开发且广泛应用于各种结构工程, 包括桥梁、汽车和其他重要高强度应用, 如核电站反应堆压力容器. 纳米钢的机械性能与应用, 在很大程度上取决于其微观组织. 通过控制析出物的大小、数量密度、分布和类型, 可以生产出抗拉强度高达2 GPa的纳米钢, 同时保持10%以上的良好拉伸延伸率及40%的面积缩小率. 此外, 通过调控各种强化机制, 纳米钢可以避免回火脆性, 从而具有优异的强度和低温冲击韧性. 通过添加适当的锰(Mn), 纳米钢可以在不牺牲其强度下(屈服强度, YS为~1100–1300 MPa; 极限抗拉强度, UTS为~1300–1400 MPa), 延展性提高3倍(总拉伸延伸率, TE约为30%). 更重要的是, 这些纳米钢有良好的可加工性和可焊性. 本文全面综述了先进纳米钢的微观结构及其性能关系. 此外, 本文对纳米钢的当前局限和未来发展进行了详细的探讨和概述.