Transition between internal and external nitridation of Ni-Ti alloys
- McMaster Univ., Hamilton, Ontario (Canada). Dept. of Materials Science and Engineering
A series of Ni-Ti alloys ranging in composition from 0.1 to 5 wt pct Ti were annealed in nitrogen gas or a nitrogen/argon gas mixture between 800 C and 1,020 C. The evolution of surface and subscale structures, along with the diffusion profile of Ti in Ni, were investigated using scanning electron microscopy and energy dispersive X-ray analysis (EDX), respectively. A strong extrusion of Ni to accommodate the excess volume of internal TiN precipitation was observed between 0.5 and 1.0 wt pct Ti at 1,020 C, where a continuous superficial layer of stoichiometric TiN begins to form. A finite difference computational algorithm was developed based upon a ternary model of simultaneous diffusion and precipitation, which generates the concentration profile of Ti in Ni and the particle distribution of TiN and subsumes a transition from internal to external nitridation. Because there is a dearth of independent thermodynamic and kinetic data on this system, the authors were forced to use parameters established by a selected minimal set of their own experiments to predict outcomes for the main body of experimental work, thereby obtaining satisfactory closure between theory and experiment.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 264079
- Report Number(s):
- CONF-941016-; ISSN 0360-2133; TRN: IM9633%%13
- Journal Information:
- Metallurgical Transactions, A, Vol. 27, Issue 6; Conference: Materials week `94, Rosemont, IL (United States), 3-7 Oct 1994; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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