WC-Co系合金の引張り変形および破壊について

概要

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Plastic deformation and fracture of WC-Co alloys in tension have been studied as a function of composition (6-24wt%Co), WC particle-size (1.3-2.4μ) and carbon concentration.<BR>Although tensile fracture-strain of the alloys is in general much less than compressive fracture-strain, the tensile stress-strain curves can completely be superposed on the compressive stress-strain curves. This result suggests that the deformation mechanisms are same in tension and in compression, i.e., of dispersion strengthening type.<BR>The tensile strengths of the alloys with an optimum carbon concentration and a fixed WC particle-size plotted against the mean free path give rise to a peak at-0.4μ. With the decrease in WC particle-size, the strength curve in general shifts towards higher strength side and the increase in ductility is also accompanied.<BR>Fractographic analysis by means of scanning electron microscopy reveals that tensile fracture is predominantly intergranular. Internal friction of the alloys in general increases with progress of the plastic deformation and also after the fracture even when the fracture occurs essentially in the elastic range. This suggests that plastic straining due to stress relaxation has occurred in the Co phase in some stage of tensile deformation.<BR>Nature of tensile fracture of the alloys was discussed in some detail on the basis of the above observations.
社団法人粉体粉末冶金協会の論文