Processing map for controlling microstructure in hot working of hot isostatically pressed powder metallurgy NIMONIC AP-1 superalloy
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The hot deformation behavior of hot isostatically pressed (HIP) NIMONIC AP-1 superalloy is characterized using processing maps in the temperature range 950 °C to 1200 °C and strain rate range 0.001 to 100 s•1. The dynamic materials model has been used for developing the pro-cessing maps which show the variation of the efficiency of power dissipation given by [2m/ (m + 1)] with temperature and strain rate, withm being the strain rate sensitivity of flow stress. The processing map revealed a domain of dynamic recrystallization with a peak efficiency of 40 pct at 1125 °C and 0.3 s•1, and these are the optimum parameters for hot working. The microstructure developed under these conditions is free from prior particle boundary (PPB) de-fects, cracks, or localized shear bands. At 100 s•1 and 1200 °C, the material exhibits inter-crystalline cracking, while at 0.001 s•1, the material shows wedge cracks at 1200 °C and PPB cracking at 1000 °C. Also at strain rates higher than 10 s•1, adiabatic shear bands occur; the limiting conditions for this flow instability are accurately predicted by a continuum criterion based on the principles of irreversible thermodynamics of large plastic flow.
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- Processing map for controlling microstructure in hot working of hot isostatically pressed powder metallurgy NIMONIC AP-1 superalloy
Metallurgical Transactions A
Volume 23, Issue 10 , pp 2849-2857
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- 1. Defence Metallurgical Research Laboratory, 500 258, Hyderabad, India
- 2. Department of Metallurgical Engineering, Banaras Hindu University, 221 005, Varanasi, India
- 3. Department of Metallurgy, Indian Institute of Science, 560 012, Bangalore, India