%0 Publication %T Analysis of Nano-hardness Distribution Near the Ferrite-martensite Interface in a Dual Phase Steel with Factorization of Its Scattering Behavior %A Reon Ando; Tomoko Matsuda; Hideo Yokota; Norio Yamashita; Ikumu Watanabe; Takashi Matsuno; Kenta Goto %8 28/02/2023 %I Iron and Steel Institute of Japan %U https://mdr.nims.go.jp/concern/publications/0c483n541 %( https://doi.org/10.2355/isijinternational.ISIJINT-2020-546 %X We investigated the local preliminary hardening of ferrite near the ferrite–martensite interfaces in a dual-phase (DP) steel. Geometrically necessary dislocations (GNDs), generated due to interfacial misfit between different phases, may cause preliminary hardening of ferrite around such interfaces. However, for nano-hardness distribution, the hardened zone was not evidently detected by scattering measurement. Thus, we factorized nano-hardness scattering to estimate the actual ferrite hardness near ferrite–martensite interfaces. First, nano-hardness was measured around a martensite island using a conical nano-indenter in the DP steel containing 10% martensite by volume. Taking into account the scattering, the nano-hardness measurement converged to the hardness of ferrite, exceeding the distance corresponding to the nano-indenter radius. Thus, a preliminary hardening zone was not detected. Subsequently, the surface of the nano-indented microstructure was polished and observed using scanning electron microscopy (SEM) by analyzing electron back scattering diffraction (EBSD). This analysis confirmed the presence of the nano-indented microstructure under ferrite. Moreover, it established that the majority of the irregularly higher nano-hardness was caused by the buried martensite under ferrite. The value of the kernel average misorientation (KAM), which is proportional to the GND density for other irregularly higher nano-hardness points, was higher for the nano-indented microstructure as compared to that of the buried martensite. On the other hand, the ferrite was expanded under the nano-indented points for the majority of the irregularly lower nano-hardness, with some exceptions. Further, soft martensite was observed to induce irregularly lower nano-hardness locally around the interface. %G English %9 Article %K dual phase steel; grains and interfaces; nanoindentation; scattering; serial sectioning %~ MDR: NIMS Materials Data Repository %W National Institute for Materials Science