Mo2FeB2硼化物系硬質合金の焼結機構と機械的性質

概要

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The sintering phenomena of Fe-6 wt%B-(0-58) wt%Mo alloys are studied by means of TG-DTA, dilatometric measurements and X-ray diffractometry. In addition, the mechanical properties of the sintered alloys are discussed. The optimum process-property relations can be summarized as follows: (1)Highest transverse rupture strength values around 200 kg/mm2 are obtained for the 48 wt%Mo alloy. (2)The 48 wt%Mo alloy consists of the Mo2FeB2 and a small amount of Fe2B as hard phases and of an Fe binder phase. (3)The Mo2FeB2 phase is formed in the temperature range 750-1090°C. The liquid phase sintering of the alloy is accomplished by two different liquid phases produced by two different reactions. The first reaction, γ-Fe+Fe2B→L1, occurs in a temperature range 1090-1150°C, this being somewhat lower than expected for the binary Fe-Fe2B system presumably due to the presence of Mo. The second reaction, γ-Fe+Mo2FeB2→L2, occurs above 1150°C. (4)The optimum sintering temperature lies slightly above the temperature at which the reaction γ-Fe+Mo2FeB2→L2 occurs.