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An experimental stainless steel containing 14Cr-20Mn was found to exhibit moderate superplastic behaviour in the temperature range 800-1000 C at strain rates of 1.0 E-4 to E-3/s. The strain rate sensitivity index was found to be insensitive to test temperatures between 825 and 875 C but varied with strain rate, reaching a maximum of about 0.5 at 3x 1.0 E-4/s. A model is proposed to estimate the rate of grain growth that occurred during superplastic deformation in terms of static grain growth, which is a function of the time and the activation energy of grain-boundary self-diffusion, and strain-enhanced growth, which is a function of strain rate and volume self-diffusion. Cavitation accompanied superplastic deformation and increased with increasing local strain, increasing temperature and decreasing strain rate. The cavitation results were analysed using strain-based and time-based models. The latter gave a more consistent estimate of the cavities present in the prestrain condition.

Additional information

Authors: FARAG M M, American University in Cairo, Department of Engineering, Cairo (EG);PIATTI G, JRC Ispra (IT)
Bibliographic Reference: Article: Materials Science and Engineering, A123 (1990) pp. 271-280
Record Number: 199011146 / Last updated on: 1994-12-01
Original language: en
Available languages: en