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Low temperature creep of hot-extruded near-stoichiometric niti shape memory alloy. part i; isothermal creep
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Noebe, R. D. Raj, S. V. |
| Copyright Year | 2013 |
| Description | This two-part paper is the first published report on the long term, low temperature creep of hot-extruded near-stoichiometric NiTi. Constant load tensile creep tests were conducted on hot-extruded near-stoichiometric NiTi at 300, 373 and 473 K under initial applied stresses varying between 200 and 350 MPa as long as 15 months. These temperatures corresponded to the martensitic, two-phase and austenitic phase regions, respectively. Normal primary creep lasting several months was observed under all conditions indicating dislocation activity. Although steady-state creep was not observed under these conditions, the estimated creep rates varied between 10(exp -10) and 10(exp -9)/s. The creep behavior of the two phases showed significant differences. The martensitic phase exhibited a large strain on loading followed by a primary creep region accumulating a small amount of strain over a period of several months. The loading strain was attributed to the detwinning of the martensitic phase whereas the subsequent strain accumulation was attributed to dislocation glide-controlled creep. An "incubation period" was observed before the occurrence of detwinning. In contrast, the austenitic phase exhibited a relatively smaller loading strain followed by a primary creep region, where the creep strain continued to increase over several months. It is concluded that the creep of the austenitic phase occurs by a dislocation glide-controlled creep mechanism as well as by the nucleation and growth of deformation twins. |
| File Size | 1346174 |
| Page Count | 24 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20130014001 |
| Archival Resource Key | ark:/13960/t3qv8ht2q |
| Language | English |
| Publisher Date | 2013-06-01 |
| Access Restriction | Open |
| Subject Keyword | Metals And Metallic Materials Titanium Alloys Creep Properties Shape Memory Alloys Nucleation Nickel Alloys Strain Distribution Martensite Tensile Creep Low Temperature Load Tests Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
