Grain refinement is one of the most effective methods for strengthening steels, but grain refinement to 1 µm or less deteriorates the ductility considerably. To evade the strength-ductility trade-off, a lamellar-structured (LS) ultrafine-grained (UFG) dual-phase (DP) ferrite/martensite (F/M) steel was produced by warm rolling an intercritical annealed low-carbon martensite and subsequent air cooling in this paper. The microstructure is similar to a short fiber reinforced composite, and the highest strength (1432 ± 15 MPa) combined with a decent ductility (16.5 ± 0.5% elongation) is achieved in DP steel. Compared with conventional equiaxed coarse-grained (CG) and UFG DP counterparts, the LS martensite in UFG DP steel can produce extra strengthening effect and is also beneficial to ductility. And the short fiber theory can predict the strength very well.

晶粒细化是强化钢最有效的方法之一，但是晶粒细化到1 µm或更小会大大降低延展性。为了避免强度-延展性的折衷，通过对临界退火的低碳马氏体进行热轧来生产层状（LS）超细晶粒（UFG）双相（DP）铁素体/马氏体（F / M）钢以及随后的空气冷却。显微组织类似于短纤维增强复合材料，在DP钢中获得了最高的强度（1432±15 MPa）和良好的延展性（16.5±0.5％的伸长率）。与常规等轴粗晶（CG）和UFG DP对应物相比，UFG DP钢中的LS马氏体可以产生额外的强化效果，并且还有利于延展性。