Evolution of Mechanical Properties in a Low Carbon Steel During Cold-Rolling and Subsequent Annealing

Among the different strengthening mechanisms of steels, grain refinement is the only method to improve both strength and toughness simultaneously. Numerous approaches, such as plastic deformation and recrystallization (PDR), high pressure torsion (HPT), equal-channel angular pressing (ECAP), etc. [1–3] are employed to reduce the grain size of materials down to submicron and even nanometers. Among these methods, PDR is one of the advanced thermomechanical processing and is a very attractive method with a number of advantages. Firstly, it can produce massive samples without micro-porosity and contamination for further mechanical testing and physicochemical examination to reveal the intrinsic properties of nanocrystalline materials. Secondly, PDR can be easily adapted to large-scale industrial production [3].One of the PDR routes to fabricate ultra-fine grained steels was developed by Tsuji et al. [4]. The process includes cold-rolling of a martensite starting microstructure in a low carbon steel and subsequent annealing. The final microstructure was reported to consist of ultra-fine ferrite grains and uniformly precipitated carbides. The formation of an ultra-fine microstructure was attributed to the fine martensite starting microstructure, which augmented the effect of plastic deformation enhancing grain subdivision [4].Based on the above consideration, the aim of this work was to explore the evolution of mechanical properties of a low carbon steel during cold-rolling and subsequent annealing at various temperatures