The formation of martensite in splat-quenched Fe-Mn and Fe-Ni-C alloys

A two-piston splat-quenching technique has been used to prepare splat-quenched Fe-Mn alloys with 0 to 20 wt % Mn, and splat-quenched Fe-Ni-C alloys with a nominal carbon content of 0.1 wt % and 0 to 40 wt % Ni. The resulting alloy microstructures have been investigated by a combination of optical and scanning electron microscopy, X-ray diffractometry, and microhardness testing; and the splat-quenched structures have been compared with the microstructures of similar alloys prepared by conventional solid-state quenching. In both alloy systems, splat-quenching produces a very small as-solidified austenite grain size, and a depression of the martensite transformation temperature as shown by an increased tendency to retain austenite to low temperatures. Because of the combination of a small austenite grain size and, therefore, fine scale martensite structure, splat-quenched martensitic alloys of Fe-Mn and Fe-Ni-C exhibit very high microhardness values.