Critical temperature for growth of martensite

• Ms may be defined as the temperature below which the formation of martensite starts upon cooling. It may also be useful to define Mg, the temperature below which martensite can grow if it is already nucleated. In order to analyze the mechanism of martensite formation, it is essential to know the difference Mg - Ms. We have tried to evaluate Mg - Ms for an Fe-C alloy with a decarburized surface zone in order to induce nucleation. The samples were studied by means of electron microprobe, serial sectioning and optical microscopy. The results indicate that Mg is surprisingly close to Ms. The possibility that Mg is controlled by growth rather than nucleation is discussed.

Nyckelord

Cooling; Grain boundaries; Growth (materials); Iron alloys; Nucleation; Optical microscopy; Phase transitions; Temperature; Critical temperature; Decarburized surface zone; Electron microprobe; Serial sectioning; Martensite

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