Details
| Original language | English |
|---|---|
| Title of host publication | Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004 |
| Editors | M. Helmus, D. Medlin |
| Pages | 32-37 |
| Number of pages | 6 |
| Publication status | Published - 2005 |
| Externally published | Yes |
| Event | Medical Device Materials II - Materials and Processes for Medical Devices Conference 2004 - St. Paul, MN, United States Duration: 25 Aug 2004 → 27 Aug 2004 |
Publication series
| Name | Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004 |
|---|
Abstract
The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.%Ni in hot-rolled and cold-drawn states. In particular we examine microstructure, transformation temperatures and mechanical behavior of deformation processed NiTi. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress induced martensite, which is critical for optimizing the mechanical properties. Deformation processing of the NiTi consisted of hot-rolling, as well as, hot-rolling then cold-drawing. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. The subsequent cold-drawing induced a high density of dislocations and martensite. Heat treatments were carried out on both materials at various temperatures for 1.5 hours. Transmission Electron Microscopy (TEM) observations revealed that Ti3Ni4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti 3Ni4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi. Copyright
ASJC Scopus subject areas
- Engineering(all)
- General Engineering
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Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004. ed. / M. Helmus; D. Medlin. 2005. p. 32-37 (Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004).
Research output: Chapter in book/report/conference proceeding › Conference contribution › Research › peer review
}
TY - GEN
T1 - Thermal processing of polycrystalline NiTi shape memory alloys
AU - Frick, C.
AU - Ortega, A.
AU - Tyber, J.
AU - Gall, K.
AU - Maier, H. J.
AU - Maksound, A. El M.
AU - Liu, Yinong
N1 - Funding Information: The U.S. authors gratefully thank financial support for this work from the Department of Energy through a Presidential Early Career Award for Scientists and Engineers (PECASE), as well as the Joint Institute for Laboratory Astrophysics (JILA) for use of their Atomic Force Microscope. The German authors gratefully thank financial support for this work from Deutsche Forschungsgemeinschaft.
PY - 2005
Y1 - 2005
N2 - The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.%Ni in hot-rolled and cold-drawn states. In particular we examine microstructure, transformation temperatures and mechanical behavior of deformation processed NiTi. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress induced martensite, which is critical for optimizing the mechanical properties. Deformation processing of the NiTi consisted of hot-rolling, as well as, hot-rolling then cold-drawing. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. The subsequent cold-drawing induced a high density of dislocations and martensite. Heat treatments were carried out on both materials at various temperatures for 1.5 hours. Transmission Electron Microscopy (TEM) observations revealed that Ti3Ni4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti 3Ni4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi. Copyright
AB - The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.%Ni in hot-rolled and cold-drawn states. In particular we examine microstructure, transformation temperatures and mechanical behavior of deformation processed NiTi. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress induced martensite, which is critical for optimizing the mechanical properties. Deformation processing of the NiTi consisted of hot-rolling, as well as, hot-rolling then cold-drawing. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. The subsequent cold-drawing induced a high density of dislocations and martensite. Heat treatments were carried out on both materials at various temperatures for 1.5 hours. Transmission Electron Microscopy (TEM) observations revealed that Ti3Ni4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti 3Ni4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi. Copyright
UR - http://www.scopus.com/inward/record.url?scp=31744434531&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:31744434531
SN - 0871708248
T3 - Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004
SP - 32
EP - 37
BT - Medical Device Materials II - Proceedings of the Materials and Processes for Medical Devices Conference 2004
A2 - Helmus, M.
A2 - Medlin, D.
T2 - Medical Device Materials II - Materials and Processes for Medical Devices Conference 2004
Y2 - 25 August 2004 through 27 August 2004
ER -