Decomposition of Retained Austenite in a High-Speed Steel GPM A30 |
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Authors: | TH Yu CY Chen JR Yang |
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Affiliation: | (1) Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan, ROC |
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Abstract: | The effect of tempering on the decomposition of retained austenite in a powder metallurgy (PM) high-speed steel, GPM A30,
has been monitored with a high-speed dilatometer. The corresponding microstructures of specimens with different tempering
cycles have been investigated by a combination of scanning electron microscopy and analytical transformation electron microscopy.
The as-quenched structure of the steel studied is composed of retained austenite, untempered martensite, and carbides. The
results indicate that the complete transformation of retained austenite can be more nearly accomplished by double or triple
tempering cycles than by a single long-time cycle. The possible transformation mechanism for the decomposition of retained
austenite during multiple tempering cycles is attributed to the invariant-plane-strain of the prior martensitic transformation
extending accommodation defects to the adjacent retained austenite, which favors further transformations in the subsequent
tempering operations.
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Keywords: | carbide transformation decomposition of retained austenite plate martensite powder metallurgy (PM) high-speed steel thermal dilatometer |
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