THE EFFECT OF LONG-TERM AGING ON THE GAMMA PRIME CHARACTERISTICS AND TENSILE PROPERTIES IN Ni-BASE SUPERALLOY K44
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. THE EFFECT OF LONG-TERM AGING ON THE GAMMA PRIME CHARACTERISTICS AND TENSILE PROPERTIES IN Ni-BASE SUPERALLOY K44. Acta Metall Sin, 2006, 42(5): 481-486 .
Abstract The effect of long-term aging on the γ’ characteristics and the mechanical properties have been investigated in a corrosion resistant nickel-base superalloy K44 aged isothermally in the temperature range of 800-900℃ up to 10000 h. SEM observation reveals that the coarsening kinetics of γ’ follows Lifshitz-Slyozof-Wagner (LSW) theory at different temperatures, with the activation energy of 255 kJ/mol for growth. Morphological instability occurs in relatively small γ’ precipitates during aging process. At room temperature (RT) and 900℃, yield strength decreases with aging temperature and aging time increasing, while fluctuation of elongation is observed. The dependence of the yield stress on particle size is explained by Labusch-Schwarz hardening theory rather than classical strengthening theory on coherency and mismatch strengthening. Shearing of strong-coupled dislocations is dominant strengthening mechanism.
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