Characterization of a low carbon low alloy steel by nanoindentation
一种低碳低合金钢的纳米压痕表征

A low carbon low alloy steel with two different types of microstructures was characterized by nanoindentation. The results indicate that the average nanoindentation hardness of martensite is at least 70% higher than that of ferrite in the dual-phase sample. Since the ultrafine martensite grain is embedded in the soft ferrite matrix, the nanoindentation hardness of martensite exhibits a substrate-effect when the indentation depth is over 40 nm. Due to more carbon atoms partitioning to austenite during intercritical process, carbon content of martensite in the dual-phase sample may be several times higher than the nominal carbon content of the steel, which makes the average nanoindentation hardness of martensite in the dual-phase sample is at least 30% higher than that in the fully martensitic sample. In addition, the possible effects of carbon partitioning on Poisson ratio and Young's modulus of martensite were discused briefly.