Effect of Plastic Deformation on the Mechanical Properties of Dual-Phase Steels Using Nanoindentation

The mechanical properties of two advanced high-strength steels (AHSS), DP 1000 and DP 1200 dual-phase (DP) grades, under deformed and undeformed conditions, were investigated using nanoindentation, and the results were compared with those obtained from the conventional methods. To this goal, 3-point bending tests were applied to induce deformation in the samples. Before and after these tests, nanoindentations were performed at different forces and indentation depths. In addition to the hardness and modulus of elasticity values of the steels, the residual stresses on the samples after deformation were obtained by using the equations suggested in the literature, also with x-ray diffraction (XRD). Finite element (FE) modeling of 3-point bending and nanoindentation were performed to obtain stress–strain curves of the materials numerically. The stress–strain curves obtained by numerical analysis agree well with those reported in the literature. The variations of the hardness and modulus of elasticity values are narrower for deeper indentation (50 nm versus 200 nm), and the effect of deformation is more pronounced on the modulus of elasticity values (10–30% increase with the deformation) while hardness values increased with the effect of deformation, 10% at most.