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Study of Temperature and Stress Effects on Phase Transformation in MP35N

Shaker Ardakani, Morteza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42367 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Asgari, Sirous
  7. Abstract:
  8. Many Investigations have been carried out on high work hardening, strengthening and secondary hardening of MP35N superalloy. In this study, behavior of MP35N under uniaxial hot compression at 600 °C with true strain of 0.05, 0.10, 0.16 and 0.22 was investigated. After calculating on stress- true strain curve, work hardening rate versus strain come out. Serrated flow has been seen in all mentioned strains. In TEM investigation on these samples, dislocations array with extended faults and micro twinning have been seen. According to Suzuki mechanism with solute partitioning and diffusion of solute, stacking fault extended. Uninterrupted separations and combinations of partial dislocations lead to jerky flow in plastic deformation. Samples that compressed at 600 °C with true strain 0.16 and 0.22, deformed at room temperature until strain about yield point and 0.22 consequently. Microstructure at yield point is dislocations array and micro twinning. Extended fault with solute diffusion at prior hot working causes increase in work hardening in comparison with sample without hot working. In deformation at room temperature with prior hot working, deformation twinning dispersed finely. Samples that compressed at 600 °C with true strain 0.05 and 0.10, after heat treating at 600 °C for 4 hours, deformed at room temperature in strain about yield point. Increase in micro hardness of sample with 0.10 hot working, indicates that secondary hardening occurred at critical hot strain is less than cold strain
  9. Keywords:
  10. Work Hardening ; Stacking Fault Energy ; MP35N Superalloy ; Secondary Hardening ; Micro Twining ; Suzuki Mechanism

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