Some features of the transformation of retained austenite

Kogan, L. I.; Éntin, R. I.

doi:10.1007/bf00819482

Cited by 2 publications

(1 citation statement)

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“…Similar observations can be found in the literature [22,[27][28][29] and are explained with carbon diffusion (partitioning) from martensite to austenite or relaxation of stresses in the microstructure. It is not clear what the dominating process is or if other unidentified mechanisms are also involved.…”

Section: Transformation To Martensitesupporting

confidence: 89%

Retained Austenite Transformation during Heat Treatment of a 5 Wt Pct Cr Cold Work Tool Steel

Rehan

Medvedeva²,

Svensson

et al. 2017

Metall Mater Trans A

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Retained austenite transformation was studied for a 5 wt pct Cr cold work tool steel tempered at 798 K and 873 K (525°C and 600°C) followed by cooling to room temperature. Tempering cycles with variations in holding times were conducted to observe the mechanisms involved. Phase transformations were studied with dilatometry, and the resulting microstructures were characterized with X-ray diffraction and scanning electron microscopy. Tempering treatments at 798 K (525°C) resulted in retained austenite transformation to martensite on cooling. The martensite start (M s ) and martensite finish (M f ) temperatures increased with longer holding times at tempering temperature. At the same time, the lattice parameter of retained austenite decreased. Calculations from the M s temperatures and lattice parameters suggested that there was a decrease in carbon content of retained austenite as a result of precipitation of carbides prior to transformation. This was in agreement with the resulting microstructure and the contraction of the specimen during tempering, as observed by dilatometry. Tempering at 873 K (600°C) resulted in precipitation of carbides in retained austenite followed by transformation to ferrite and carbides. This was further supported by the initial contraction and later expansion of the dilatometry specimen, the resulting microstructure, and the absence of any phase transformation on cooling from the tempering treatment. It was concluded that there are two mechanisms of retained austenite transformation occurring depending on tempering temperature and time. This was found useful in understanding the standard tempering treatment, and suggestions regarding alternative tempering treatments are discussed.

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Section: Transformation To Martensitesupporting

confidence: 89%