抄録
Fe-C system alloys were prepared by mechanical alloying and powder metallurgy (MA-PM). Elemental powders of iron and graphite with various carbon concentrations were mechanically alloyed (MAed) by using a planetary ball mill in argon atmosphere. The MAed powders were then characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). During MA, the particle refinement, formation of super-saturated solid solution and Fe/C amorphous occur and their degrees are influenced by carbon concentration in the mixed powders. The MAed powders with 4-10 mass% carbon concentration were hot isostatic pressed (HIPed) and with 0.4-2 mass% were hot pressed (HPed) at both lower and higher temperatures than the eutectoid transformation point A1. The sintered compacts were characterized by Vickers hardness test, tensile test and scanning electron microscopy (SEM). Both the HIPed and HPed compacts obtained in the present study have very fine microstructures in which very fine cementite dispersed in very fine ferrite matrix. Mechanical properties of the HPed compacts of Fe-C system with hypo-eutectoid composition are comparable with those of standard steels. Thus, MA and PM is a new technique of near net-shape to gain steels with excellent mechanical properties without thermal refining and alloying elements.
