Influence of microstructural parameters on nanohardness of various dual-phase steels: Experiment, Finite Element simulation and Statistical analysis

Abstract

This study aims to achieve insight related to the role of various microstructural parameters on nanohardness of different phases in ferrite-martensite (FM), ferrite-bainite (FB) and ferrite-pearlite (FP) steels. Low-carbon microalloyed steel has been subjected to suitable heat treatment schedules to develop FM, FB and FP dual-phase (DP) microstructures with nearly the same amount of ferrite. Macro, micro, and nanohardness values and tensile properties of the developed DP steels have been measured while their microstructures have been characterized. It has been found that the characteristics of hard phase strongly affect the nanohardness of the ferrite phase. Load-depth profiles of diverse phases obtained from the nanoindentation tests have been simulated by the finite element (FE) technique. The dislocation-based model has been modified to estimate the flow behavior of constituent phases which have been provided as input to the FE simulations. The predicted nanoindentation load-depth profiles are found to be in good agreement with the experiment ones. Subsequently, FE simulations have been performed by incorporating the microstructural parameters to predict the nanohardness of individual phases in the developed DP microstructures. Finally, statistical analyses following the Taguchi method and ANOVA have been conducted to demonstrate the influence of different microstructural parameters on nanohardness in various DP steels. It has been revealed that the nanohardness values of constituting phases are significantly influenced by the percentage of carbon and the hardness ratio of two phases in FM, FB and FP DP steels except the pearlite for which the interlamellar spacing is the most contributing factor.