The effect of solidification conditions on phase transformation of iron matrix of Fe-25mass%Cr-C-B alloys

This is the authors' abstract. We don't add key points for this paper.

M2B, M23(C,B)6 and M7(C,B)3 compound phases which constitute the eutectic structures of Fe-25mass%Cr-C-B alloys vary depending on both carbon and boron content. The composition of the matrix structure also varies with each eutectic structure. Due to this, it is presumed that the transformation behavior of the matrix is affected by the solidification rate of the cast material. In the present research, three kinds of molds are used in changing the solidification rate, namely, an exothermic mold, a sand mold and a metal mold. The alloys made from each mold are subjected to thermal expansion tests in order to clarify the transformation behavior both in furnace cooling and air cooling conditions. The results indicate that the hardness of each alloy is higher in a mold where solidification is faster. Most of the alloy transform to martensite during air cooling. In furnace cooling, low carbon with high boron alloys transform to bainite, whereas, high carbon alloys transform to pearlite. Furthermore, alloys with lower carbon content have ferritic matrix which does not transform to any other structure in any cooling condition.