Papers by Author: Tsuyoshi Yukimoto

Abstract: Although forming of porous metal is demanded for industrial applications, the deformation characteristics have not been investigated sufficiently. In this study, lotus-type porous copper is processed by multi-pass cold rolling. At the early stage of rolling, the elongation of the porous copper in the rolling direction is small, and the porosity decreases almost linearly with the total reduction in thickness. It is found that pass schedule with small rolls and with small reduction per pass is effective to suppress pore closure. Hardness of the porous copper increases almost linearly with total reduction. If the effective total reduction is considered, the hardness change is similar to that of a nonporous copper.

Abstract: 1050 aluminum sheet was cold-rolled by 50% with mineral oil. Hardness was measured on longitudinal section through the thickness of the rolled sheet. The overall hardness statistics of the as-rolled sheet followed the normal (Gaussian) distribution. Though the sheet was rolled under good lubrication, considerable redundant shear deformation was introduced beneath the surfaces by friction. The layers beneath the surfaces showed higher hardness than the center. The hardness subset statistics in one layer in the thickness also followed normal distribution. Isothermal changes in Vickers hardness statistics and in tensile properties during annealing at 548K were investigated. Beneath the surfaces, the recrystallization initiated and completed earlier than the center. The fully recrystallized sheet also shows the normal distribution of hardness, however the standard deviation is much smaller than that before annealing. The layers beneath the surfaces show lower hardness than the center after recrystallization. The partially recrystallized sheet shows bi-modal distribution of hardness. The partially recrysrallized sheet shows slightly better tensile-elongation balance than both the as-rolled sheet and the sheet-fully recrystallized.