Mechanical behavior of the in situ composite alloys in the Al-Ni-Ti system near the Li{sub 2} phase field
- Univ. of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering
The Vickers microhardness (VHN) test at room temperature and compressive tests at temperatures up to 1,000 C were carried out on the three-phase composite alloy, consisting of the L1{sub 2}, face-centered cubic (fcc) Al{sub 2}TiNi, and Al{sub 2}Ti intermetallic phases, in the Al-Ti-Ni system. The microhardness tests indicated that the fcc Al{sub 2}TiNi phase was very hard and brittle. Comparatively, the L1{sub 2} phase was softer and more crack resistant. A considerable hardening was noticed due to the precipitation of Al{sub 2}Ti within L1{sub 2}. In addition, the VHN of the L1{sub 2} phase was found to increase with the combined content of nickel and titanium without the presence of any observable precipitates. Under compressive loading at room temperature, microcracks nucleated in the fcc Al{sub 2}TiNi phase. These cracks propagated catastrophically at a stress barely approaching yield stress, resulting in nil ductility. This behavior was observed up to 800 C. Between 900 C and 950 C, brittle-to-ductile transition in compressive behavior was observed for the three-phase alloy. Compressive ductility of the order of 80 pct was observed at 1,000 C. The mechanism of dynamic recrystallization was found to be operative at 1,000 C. Metallographic investigation revealed new recrystallized grains in the primary L1{sub 2} matrix. However, the oscillatory nature of the true stress-true strain curve could not be explained with the help of the existing model of dynamic recrystallization.
- OSTI ID:
- 203519
- Journal Information:
- Metallurgical Transactions, A, Vol. 27, Issue 1; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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