Takuya Takashita

Influence of Microstructure on Coercive Force of Pure Iron Powder Cores

The recrystallization behavior of pure iron powder cores during the annealing process is visualized as Grain Orientation Spread (GOS) maps with an SEM/EBSD analysis. It is found to be significantly heterogeneous, leading to a heterogeneous dislocation density distribution. Nevertheless, a conventional dislocation pinning model well describes the coercive force behavior if the average dislocation density is applied. The pinning model is modified to separate the influence of the grain boundary pinning, and the relationship between the coercive force and the microstructure is discussed comprehensively. [doi:10.2320/matertrans.Y-M2018821]

Precipitation Morphology in Al-Mg-Si-Sc-Zr Hot-Rolled Sheet

In order to clarify the morphology and the elemental distribution of particles in an Al-Mg-Si-Sc-Zr alloy, microstructural observations and elemental analyses were carried out by transmission electron microscopy (TEM), scanning TEM, three-dimensional electron tomography and energy dispersive X-ray spectroscopy. The Al-Mg-Si-Sc-Zr alloy was cast, homogenized and hot-rolled. Two types of Al3(Sc, Zr) particles with L12 structure were observed in the hot-rolled sheet: spherical particles about 50 nm in diameter, and rod-like particles about 50 nm in diameter and 200nm in length. All particles have the core-shell structure with the core enriched with Sc and the shell enriched with Zr atoms. One type of spherical particles have a semi-coherent relationship with the matrix, while another type of spherical particles shows a cylindrical core morphology and have an incoherent relationship with the matrix. In summary, it is concluded that the rod-like particles, the coherent spherical particles and the incoherent particles are formed during casting, homogenized treatment and hot-rolling, respectively.