High-performance dispersion-strengthened Cu-8 Cr-4 Nb alloy
- Univ. of California, Davis, CA (United States). Chemical Engineering and Materials Science Dept.
- National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center
- Case Western Reserve Univ., Cleveland, OH (United States)
A new high-temperature-strength, high-conductivity Cu-Cr-Nb alloy with a Cr:Nb ratio of 2:1 was developed to achieve improved performance and durability. The Cu-8 Cr-4 Nb alloy studied has demonstrated remarkable thermal and microstructural stability after long exposures at temperatures up to 0.98 T{sub m}. This stability was mainly attributed to the slow coarsening kinetics of the Cr{sub 2}Nb precipitates present in the alloy. At all temperatures, the microstructure consists of a bimodal and sometimes trimodal distribution of strengthening Cr{sub 2}Nb precipitates, depending on precipitation condition, i.e., from liquid or solid solution, and cooling rates. These precipitates remain in the same size range, i.e., large precipitates of approximately 1 {micro}m and small precipitates less than 300 nm, and effectively pin the grain boundaries, thus retaining a fine grain size of 2.7 {micro}m after 100 hours at 1,323 K. This grain-boundary pinning and sluggish coarsening of Cr{sub 2}Nb particles explain the retention of good mechanical properties after prolonged holding at very high temperatures, e.g., two-thirds of the original yield strength after aging for 100 hours at 1,273 K. The main sources of strengthening are the Hall-Petch and Orowan mechanisms due mostly to small particles. The coarsening kinetics of the large precipitates are most likely governed by grain-boundary diffusion and, to a lesser extent, volume diffusion mechanisms.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 116034
- Journal Information:
- Metallurgical Transactions, A, Vol. 26, Issue 9; Other Information: PBD: Sep 1995
- Country of Publication:
- United States
- Language:
- English
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