Gamma prime-phase stability in model nickel-aluminum-molybdenum alloys
The objective was to study the effect of variations in lattice disregistry delta between matrix and ..gamma..' precipitates on coarsening kinetics, particle shape and bulk mechanical properties in several Ni-rich Ni-Al-Mo alloys. Alloy 1 (84.7Ni-10.2Al-5.1Mo atomic %) had the highest room temperatures delta, +0.6% as determined by standard Debye-Scherrer powder x-ray techniques after 200 hours aging at 750/sup 0/C, compared to 0.17% for Alloy 2 (83.9Ni-8.2Al-7.9Mo) and nearly zero for alloy 3 (83.7Ni-6.5Al-9.8Mo). The lattice disregistries at 750/sup 0/C calculated from thermal-expansion data were +0.4%, 0.0%, and -0.1% in alloys 1 through 3 respectively. The volume fraction of ..gamma..' in each alloy measured after aging at 750/sup 0/C for 400 hours was roughly constant at 10%. TEM coherency strain analysis indicated that the /sup -/'/..gamma..' interface was fully coherent at all particle sizes. Based on this observation, a first-order relationship between constrained and unconstrained lattice disregistry was derived. During isothermal aging at 750/sup 0/C, alloy 1 exhibited the fastest ..gamma..' growth rate and alloy 3 the slowest.
- Research Organization:
- Northwestern Univ., Evanston, IL (USA)
- OSTI ID:
- 6893159
- Country of Publication:
- United States
- Language:
- English
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