Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe–Cu Alloys with Addition of Ni

다국어 초록 (Multilingual Abstract)

α/γ phase transformations occurring in Fe–10Cu–xNi alloys (0 ≤ x ≤ 15 in mass%) were studied using X-ray diff raction,scanning electron microscopy, electron back scattered diff raction, transmission electron microscopy and chemical analysis,combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobeanalysis with wavelength dispersive spectrometry. The infl uence of cooling rate on the microstructure was investigatedusing ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastabletransformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate.
Moreover, most of the Cu phase precipitates on cooling giving rise to a fi ne distribution of Cu particles in the ferrite grains.
For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in thequenched alloy for each composition. The change in hardness is correlated to the Effect of Ni solid solution, transformationstructure and size of Cu particles.

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