| To investigate the effects of hard eye structure on the mechanical properties of BMC (black heart malleable cast iron), a harder second phase was formed around the temper carbon by carbon diffusion. (rapid heating) Index, n, in the rate equation for the austenitization (Johnson-Mehl equation) was 1.4. It was found that, althouth the hardness increased considerably, the impact strength of BMC having a pearlitic structure surrounding the temper carbon has inferior to that of BMC having not hard eye structure, but the decrease in the impact strength was not as large as when the tempered martensitic structure was formed. Also BMC showed a change from ductile to a brittle mode of fracture with increasing the volume fraction of hard eye structure. |
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