Nanoindentation characterization of strengthening mechanism in a high strength ferrite/martensite steel

摘要

A 0.1C5Mn3Al steel with laminated ferrite/martensite and layered ferrite/martensite microstructures was processed by hot-rolling, cold forging and subsequent annealing. Tensile tests revealed that hot rolled sample (laminated) and cold forged + 650 degrees C annealed sample (layered) showed similar tensile strengths but different elongations. It is confirmed that laminated structure is good for retaining elongation. Furthermore, nanoindentation tests were performed at locations at or near interfaces and in the ferrite or martensite matrix, revealing that the nanohardness difference across the interface is important in affecting the elongation of the material. The underlying mechanisms were discussed with regarding to the dislocation-interface interactions.