Strength of Initially Virgin Martensites at -196 C After Aging and Tempering.
Technical rept. Oct 80-Sep 81,
MASSACHUSETTS INST OF TECH CAMBRIDGE
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The compressive strength at -196 C of martensites in Fe-O.26C-24Ni, Fe-O.4C-21Ni, and Fe-O.4C-18Ni-3Mo alloys, all with sub-zero Ms temperatures, has been determined in the virgin condition and after one hour at temperatures from -80 to 400 C. The effects of ausforming 20 reduction in area of the austenite by swaging at room temperature prior to the martensitic transformation were also investigated. For the unausformed martensites, aging at temperatures up to 0 C results in relatively small increases in strength. Above 0 C, the age hardening increment increases rapidly, reaching a maximum at 100 C during the carbon clustering stage and prior to the precipitation of carbides. Above C, the strength decreases continuously with increasing tempering temperature except for the molybdeum-containing alloy, which exhibits secondary hardening on tempering at 400 C. For the measurement martensites, the response to aging at sub-zero temperatures is greater than for unausformed material. Strength again passes through a maximum on aging at 100 C. However, on tempering just above 100 C, the ausformed materials show a slower rate of softening than the unausformed martensites. The strengthening produced by the ausforming treatment is largest for the Fe-0.4C-18Ni-Mo alloy, but there is no evidence of carbide precipitation in the deformed austenite to account for this effect of molybdenum. Author
- Metallurgy and Metallography
- Fabrication Metallurgy