Preliminary Results of Activated Sintering Mechanism and Grain Boundary Prewetting/premelting in Nickel-doped Tungsten
- Clemson University
- ORNL
Supported by prior lattice-gas and phase-field simulations, we proposed that nanoscale intergranular and surficial amorphous films in multicomponent ceramic materials can be treated as a case of combined interfacial prewetting and premelting. Consequently, a class of parallel interfacial phenomena, i.e., coupled interfacial adsorption and disordering, is anticipated to occur in multicomponent metallic alloys. An exploratory study was carried out wherein grain boundary segregation in a model binary metallic alloy (Ni-doped W) was characterized as a function of temperature and dopant concentration. Doped specimens were prepared using high purity chemicals, sintered in flowing H2/N2 mixture, and examined using Auger spectroscopy and electron microscopy. Preliminary results are presented and discussed with respect to a prewetting/premelting model versus the classical Langmuir-McLean and BET models. An additional goal of this study is to resolve the long-standing mystery of solid-state activated sintering mechanism for nickel-doped tungsten. Use of ultra-pure materials confirmed the occurrence of nickel activated sintering of tungsten in the solid-state. We demonstrated that, contrary to the previous belief, Ni-rich secondary bulk phase does not penetrate along GBs and the solid-state activator should be a nanoscale interfacial phase that does not appear in the bulk phase diagram. The solid-state activated sintering in the model metallic system of Ni-doped W is therefore attributed to the enhance diffusion in a coupled grain boundary disordering and adsorption region, analogous to activated sintering via accelerated mass transport in nanoscale intergranular and surficial amorphous film in the model oxide system of Bi2O3-doped ZnO.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Temperature Materials Lab. (HTML)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 978216
- Resource Relation:
- Conference: Annual Meeting of the American Ceramic Society, Baltimore, MD, USA, 20050410, 20050410
- Country of Publication:
- United States
- Language:
- English
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