Toughness of Nickel-Molybdenum Composites.
Abstract
The correlation between toughness, microstructure, and interface form was examined for nickel-molybdenum composites (Vf 0.08 and 0.20) in the diffusion-bonded condition and following elevated-temperature exposure. Instrumented Charpy tests were conducted on subsize specimens notched perpendicular to the direction of reinforcement. By testing above (ambient) and below the ductile to brittle transition temperature (DBTT) of the wire reinforcement, a direct comparison of impact response of ductile matrix-ductile fiber and ductile matrix-brittle fiber systems was possible. Composites exhibited a high level of toughness for all combinations of Vf, exposure history, and impact temperature; Charpy values were in the range 28-36 ft.lbs. (39-48.7J) and 10-19 ft.lbs. (13.5-25.7J) for Vf levels of 0.08 and 0.20, respectively. For each combination of test temperature and composite structure, increasing the level of reinforcement lowered toughness. Wire necking occurred at both Vf levels in the as-fabricated condition at room temperature. Pull-out was restricted to the lower volume fraction composites. Multiple fiber fracturing was a characteristic feature of low-temperature impact testing. Impact energy for the ductile matrix-brittle fiber condition can be predicted from the Cooper-Kelley model if an effective flow-stress is used for the matrix to accommodate work-hardening. A micromechanical model was developed for the ductile fiber condition which allowed for prediction of impact energy from tensile behavior of the constituents, and which accounted for the change in toughness associated with interface intermetallic compounds. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1975
- Accession Number
- ADA033502
Entities
People
- Alan Lawłey
- S. J. Burden
Organizations
- Drexel University