70.
Morphology and geometry of melted zones, cooling rates, microstructure and microhardness in the laser-glazed Fe-4%C-10%Sn alloy have been investigated. The computer simulation on the basis of the moving gaussian source model was used successfully to predict the maximum width and depth of the melted zone and the cooling rate. The microstructure from the surface to the bottom of the laser-melted zone is a non-crystalline phase, dendritic grains and a microcrystalline zone successively. Values of the average
d-spacing of the non-crystalline phase are 0.205
6 and 0.121
9nm, respectively; twinned martensites, having an axial ratio
c/a of 1.128, existed in dendritic grains, and carbides of Fe
3 C at the interdendritic regions; the microcrystalline zone was composed of -Fe and a new bet (
a=0.415 nm,
c=0.955 nm) phase. The different microstructure in the melted zone can be explained by the results of the heat flow calculation. A fine eutectic structure (-Fe + Fe
3C) was observed in heat-affected zones. Microhardness of the eutectic structure can be predicted by the empirical relation of fracture stress to the interlamellar spacing of pearlite.
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