Effect of stress-assisted aging on stress induced martensitic transformation in hot-rolled
Ni-rich 50.7at. Ni%-Ti alloy has been investigated. Alloys are aged freely and under 20
MPa, 100 MPa, and 200 MPa stress at 400
o
C for 90 minutes. Aging procedure affected
both stress-induced and thermally induced transformation behavior. Superelasticity
behavior is correlated with the multistep transformation in aged Ni-rich NiTi alloys and the
aging stress level is found to be effective. Relative to the free aged alloy, the alloy aged
under 20 MPa exhibited a slight and the alloy aged under 100 MPa exhibited a
considerable reduction, whereas the alloy aged under 200 MPa exhibited an increase in the
critical transformation stress. DSC studies have shown that the transformation is multistep
for freely aged and aged under 20 MPa alloys, whereas it is single step and two-step for
alloys aged under 100 MPa and 200 MPa, respectively, and this has been attributed to the
effect of stress on nucleation and growth rates. As a result of the different response
mechanisms to the applied stress upon loading during superelasticity testing, the recovered
strain amounts varied considerably depending on the aging conditions and the test
temperatures.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12613184/index.pdf |
| Date | 01 May 2011 |
| Creators | Sargin, Irmak |
| Contributors | Bor, Sakir |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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