Electron microscopy and diffraction of ordering in Ni-W alloys
Journal Article
·
· Acta Metallurgica et Materialia
- Steel Authority of India, Ranchi (India). Research and Development Centre for Iron and Steel
- Indian Inst. of Science, Bangalore (India)
Electron microscopy and diffraction studies of ordering in stoichiometric Ni-20%W and off-stoichiometric Ni-15%W alloys have been carried out. The specimens of Ni-20%W were first 1,398 K for 4 h and then quenched rapidly into water. Short range order (SRO) spots were observed at {l_brace}1 1/2 0{r_brace}* positions. Two hitherto unknown metastable phases: D{sub 2h}{sup 25}-Ni{sub 2}W and D0{sub 22}-Ni{sub 3}W were observed in the diffraction patterns. Long range order (LRO) transformations were studied at 1,103 and 1,213 K. Kinetics and mechanism of transformations have been identified. Ni-15%W specimens were solution treated at 1,523 K for 1 h followed by quenching in water. SRO spots similar to those found in Ni-20%W were observed in this alloy as well. The transition to LRO was studied at 1,093 K. Distinct Ni{sub 4}W precipitates could be observed after 5 h of annealing at this temperature. After 100 h of annealing precipitates were found to grow into faceted shape coherent with the disordered matrix. After prolonged annealing for over 150 h the Ni{sub 4}W precipitates began to lose coherency by the generation of misfit dislocations. The microstructural observations have been compared for the stoichiometric and off-stoichiometric alloys.
- OSTI ID:
- 72441
- Journal Information:
- Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 6 Vol. 43; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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