Comparative Effect of Rapid Dendrite Growth and Element Addition on Microhardness Enhancement of Fe-Based Alloys

Herein, we adopted alloying and rapid-dendrite-growth methods to improve the mechanical properties of Fe-based alloys. Three molten alloys including Fe-5Ni-5Mo-5Ge, Fe-5Ni-5Mo-5Ge-SCo, and Fe-5Ni-5Mo-5Ge-5Co-5Si were undercooled, during which (alpha Fe) dendrites grew rapidly with the decrease of temperature (i.e., increase of undercooling). The rapid growth of (alpha Fe) dendrites in the Fe-5Ni-SMo-SGe-5Co alloy at a high rate of 31.8 ms(-1) caused by a large undercooling more effectively enhanced the microhardness than a Co addition did. In comparison, because of the great disparity of atom size and valence electron number between Fe and Si, a further Si addition suppressed the (aFe) dendrite growth while dramatically increasing the Vickers microhardness of the Fe-5Ni-5Mo-5Ge-5Co-5Si alloy to H-V 622.