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Kinetics of static strain aging in polycrystalline nial-based alloys
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Noebe, R. D. Weaver, M. L. Kaufman, M. J. |
| Copyright Year | 1996 |
| Description | The kinetics of yield point return have been studied in two NiAl-based alloys as a function of aging time at temperatures between 300 and 700 K. The results indicate that the upper yield stress increment, Delta sigma(sub u) (i.e., stress difference between the upper yield point and the final flow stress achieved during prestraining), in conventional purity (CP-NiAl) and in high purity carbon-doped (NiAl-C) material first increased with a t(exp 2/3) relationship before reaching a plateau. This behavior suggests that a Cottrell locking mechanism is the cause for yield points in NiAl. In addition, positive y-axis intercepts were observed in plots of Delta sigma(sub u) versus t(exp 2/3) suggesting the operation of a Snoek mechanism. Analysis according to the Cottrell Bilby model of atmosphere formation around dislocations yields an activation energy for yield point return in the range 70 to 76 kJ/mol which is comparable to the activation energy for diffusion of interstitial impurities in bcc metals. It is, thus, concluded that the kinetics of static strain aging in NiAl are controlled by the locking of dislocations by Cottrell atmospheres of carbon atoms around dislocations. |
| File Size | 678427 |
| Page Count | 10 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19970022576 |
| Archival Resource Key | ark:/13960/t6g20xf2f |
| Language | English |
| Publisher Date | 1996-01-01 |
| Access Restriction | Open |
| Subject Keyword | Metallic Materials Temperature Dependence Transition Metals Crystal Dislocations Interstitials Polycrystals Nickel Aluminides Precipitation Hardening Carbon Prestressing Time Dependence Doped Crystals Impurities Yield Point Body Centered Cubic Lattices Activation Energy Strain Hardening Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
