Details
| Original language | English |
|---|---|
| Pages (from-to) | 19-27 |
| Number of pages | 9 |
| Journal | Journal of Engineering Materials and Technology, Transactions of the ASME |
| Volume | 121 |
| Issue number | 1 |
| Publication status | Published - Jan 1999 |
| Externally published | Yes |
Abstract
Transmission electron microscopy is used to determine the microstructures of a Ti- 50.8 at% Ni alloy given different aging treatments. Two different peak-aging treatments are shown to result in disk shaped semi-coherent Ti3Ni4 precipitates with a diameter ranging from 50 nm to 200 nm depending on the aging temperature. In the peak-aged materials, strong strain fields are clearly visible on TEM micrographs. An Eshelby based model is used to predict the local stress fields due to the differences in the lattice parameters of the precipitates and surrounding matrix. The position dependent local stress fields are then resolved onto the 24 different martensite correspondence variant pairs (CVP’s). It is further demonstrated that due to the unique orientation relationship that exists between the precipitate variants and the martensite CVP’s, the local resolved shear stresses are extremely large on some CVP’s and negligible on others. When the Ni rich NiTi is over-aged, it is found that the precipitates coarsen to approximately 1000 nm, they become in-coherent, and the local stress fields disappear. It is also determined that after over-aging the average composition of the matrix drops from 50.8 at% Ni to approximately 50.4 at% Ni. In a subsequent paper (part II) the results here are used to explain the dependence of the critical transformation stress levels and martensite start temperatures on the aging treatment.
ASJC Scopus subject areas
- Materials Science(all)
- General Materials Science
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
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In: Journal of Engineering Materials and Technology, Transactions of the ASME, Vol. 121, No. 1, 01.1999, p. 19-27.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - The influence of aging on critical transformation stress levels and martensite start temperatures in NiTi
T2 - Part I- Aged microstructure and micro-mechanical modeling
AU - Gall, Ken
AU - Sehitoglu, Huseyin
AU - Chumlyakov, Yuriy I.
AU - Kireeva, Irina V.
AU - Maier, Hans J.
PY - 1999/1
Y1 - 1999/1
N2 - Transmission electron microscopy is used to determine the microstructures of a Ti- 50.8 at% Ni alloy given different aging treatments. Two different peak-aging treatments are shown to result in disk shaped semi-coherent Ti3Ni4 precipitates with a diameter ranging from 50 nm to 200 nm depending on the aging temperature. In the peak-aged materials, strong strain fields are clearly visible on TEM micrographs. An Eshelby based model is used to predict the local stress fields due to the differences in the lattice parameters of the precipitates and surrounding matrix. The position dependent local stress fields are then resolved onto the 24 different martensite correspondence variant pairs (CVP’s). It is further demonstrated that due to the unique orientation relationship that exists between the precipitate variants and the martensite CVP’s, the local resolved shear stresses are extremely large on some CVP’s and negligible on others. When the Ni rich NiTi is over-aged, it is found that the precipitates coarsen to approximately 1000 nm, they become in-coherent, and the local stress fields disappear. It is also determined that after over-aging the average composition of the matrix drops from 50.8 at% Ni to approximately 50.4 at% Ni. In a subsequent paper (part II) the results here are used to explain the dependence of the critical transformation stress levels and martensite start temperatures on the aging treatment.
AB - Transmission electron microscopy is used to determine the microstructures of a Ti- 50.8 at% Ni alloy given different aging treatments. Two different peak-aging treatments are shown to result in disk shaped semi-coherent Ti3Ni4 precipitates with a diameter ranging from 50 nm to 200 nm depending on the aging temperature. In the peak-aged materials, strong strain fields are clearly visible on TEM micrographs. An Eshelby based model is used to predict the local stress fields due to the differences in the lattice parameters of the precipitates and surrounding matrix. The position dependent local stress fields are then resolved onto the 24 different martensite correspondence variant pairs (CVP’s). It is further demonstrated that due to the unique orientation relationship that exists between the precipitate variants and the martensite CVP’s, the local resolved shear stresses are extremely large on some CVP’s and negligible on others. When the Ni rich NiTi is over-aged, it is found that the precipitates coarsen to approximately 1000 nm, they become in-coherent, and the local stress fields disappear. It is also determined that after over-aging the average composition of the matrix drops from 50.8 at% Ni to approximately 50.4 at% Ni. In a subsequent paper (part II) the results here are used to explain the dependence of the critical transformation stress levels and martensite start temperatures on the aging treatment.
UR - http://www.scopus.com/inward/record.url?scp=0032762550&partnerID=8YFLogxK
U2 - 10.1115/1.2815993
DO - 10.1115/1.2815993
M3 - Article
AN - SCOPUS:0032762550
VL - 121
SP - 19
EP - 27
JO - Journal of Engineering Materials and Technology, Transactions of the ASME
JF - Journal of Engineering Materials and Technology, Transactions of the ASME
SN - 0094-4289
IS - 1
ER -