Estimation of Strength Properties from Microhardness Results in Dual Phase Steels with Different Martensite Volume Fraction

This study is about the effect of the martensite volume fraction and indentation load on microhardness profiles of dissimilar types Dual Phase steels and DC04 mild steel. Experimental investigations were performed by mickrovickers method with using of eight different indentation loads from 0.01 kp up to 1 kp. Besides, microscope and tensile tests were carried out to complete the estimation.The hardness profiles show similar characteristics in case of all examined steels independent from the microstructure. In the lowest load ranges at 0.01 and 0.025 kp (HV0.01 and HV0.025), there are no appropriate approximations with the martensite volume fraction, due to the high deviation of the hardness results which caused by the little indentation geometry. In higher ranges, above 0.05 kp (HV0.05), linear evaluations could be applicable. With the utilization of the fitted parameters, a definite relationship is reported in the hardness values and even in the strength and elongation properties with the martensite content. Based on these correlations such contexts are added which make contact between microhardness and strength values for the practice. The discrepancy between the measured and calculated results stay under 10 HV which is less than 5%