放電プラズマ焼結された超微細粒鉄の硬さにおよぼす焼結時間と圧力の影響

Abstract

Nanocrystalline iron powders with grain size of 13nm were prepared by ball-milling. The nano-structured iron powders were consolidated into discs with a diameter of 30 or 50 mm by Spark Plasma Sintering at 550°C under pressures between 80 to 220 MPa. The average grain size of the consolidated discs is about 80 nm. It does not depend on the sintering time at constant pressure. The Vickers hardness of the superfine grained iron sintered for 600 s with 220 MPa is 470 Hv. The value is plotted on the linearly extrapolated line of the Hall-Petch relationship obtained by Malow and Koch in the study on the grain size smaller than 40 nm.