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- Title
Mechanisms of Shock Strength Exhibited by a Nickel-Rich Nickel-Titanium-Hafnium Alloy.
- Authors
Knapp, Tyler; Amin-Ahmadi, Behnam; Turnage, Scott; Mills, Sean H.; Thadhani, Naresh N.; Noebe, Ronald D.; Williams, Cyril L.; Stebner, Aaron P.
- Abstract
Nickel-rich NiTiHf alloys that are heat treated to strengthen the microstructures with a dense distribution of Ni4Ti3 nanoprecipitates exhibit very high strengths and good quasi-static indentation resistance and rolling contact fatigue performances. To determine whether these properties are maintained at high rates of loading, in situ and recovery flyer plate impact shock experiments are performed on a Ni54Ti45Hf1 alloy at impact velocities ranging from approximately 150ms-1 (2.5 GPa) to 700ms-1 (12.40 GPa). Analysis of shocked samples indicated less cracking is observed to emanate from spall failures resulting from impact velocities greater than 250ms-1 (4.23 GPa), concurrent with observations of intragranular microbands within the microstructures. Analyses show clear evidence that, like responses to quasi-static loading, martensitic phase transformation occurs upon shock compression in all cases. However, dissimilarly, for the higher impact velocities it reverses upon stress release, leaving behind microbands that show no evidence for retained martensite and within which the Ni4Ti3 nanoprecipitates dissolved. These results indicate that strainrate dependence of these SMAs under shock loading is not only governed by the expected physics of rate-dependence of the martensitic transformations themselves but may also be enhanced by inelastic deformation mechanisms that result in precipitate dissolution.
- Subjects
MARTENSITIC transformations; HEAT treatment; SHAPE memory alloys; IN situ processing (Mining); ALLOYS; PHASE transitions; ROLLING contact fatigue
- Publication
Advanced Engineering Materials, 2023, Vol 25, Issue 22, p1
- ISSN
1438-1656
- Publication type
Article
- DOI
10.1002/adem.202300977