Extrusion of nickel–titanium alloys Nitinol to hollow shapes
description
Transcript of Extrusion of nickel–titanium alloys Nitinol to hollow shapes
Extrusion of nickel–titanium alloys Nitinol to hollow shapes
Author: K. MüllerPresenter: Joshua FurnerDate: 16 September 2009
Function of Paper
• Describe results of hot extrusion of NiTi alloys• Development of extrusion principles for NiTi
alloys
References• 1. D. Stöckel, et al., Legierungen mit Formgedächtnis: Grundlagen-Werkstoffe-Anwendungen,
Kontakt & Studium, Band 259, Expert Verlag Renningen Malmsheim, 1988.• 2. D. Stöckel, Formgedächtnis und Pseudoelastizität von Nickel–Titan-Legierungen. Metall. 41
(1987), p. 5. • 3. H.-P. Kehrer and H. Nußkern, Erhöhung der umwandlungstemperatur von formgedächtnis-
elementen durch konstruktive maßnahmen. Metall. 46 (1992), p. 7. • 4. T.W. Duerig, A.R. Pelton and D. Stöckel, The use of superelasticity in medicine. Metall. 50
(1996), p. 9. • 5. W. Thedja and K. Müller, Strangpressen von superelastischen NiTi-Legierungen. Metall. 52
(1998), p. 12. • 6. K. Mueller, Grundlagen des Strangpressens, Expert Verlag Renningen Malmsheim, 1995.
ISBN 3-8169-1071-8.• 7. K. Mueller, E. Hellum, Indirect tube extrusion of dispersion strengthened aluminum, in:
Proceedings of the Third World Congress on Aluminum, Aluminum 2000, Limassol, Cyprus, April 15–19, 1997.
• 8. L. Tillmann, K. Müller, W. Thedja, H. Nußkern, Massivumformung von Nickel–Titan, ein Werkstoff mit außergewöhnlichen Eigenschaften, in: Neuere Entwicklungen in der Massivumformung, 1999, MAT INFO Werkstoff-Informations-Gesellschaft. ISBN 3-88355-282-8.
Technical details
• This paper discusses the extrusion process of a material with high deformation resistance
• Consideration is taken in material selection for die design
• Comparison of Direct and Indirect methods
Parameters• Friction force• Die force• Ram displacement• Extrusion ratio• Deformation resistance• Temperature
• Deformation resistance
• Specific Extrusion Pressure
• Extrusion Ratio
Design Principle• Indirect extrusion used because of reduced
friction forces• High affinity between NiTi and steel results in
welding• Cu canning of NiTi billet protects against this• Copper chosen because of its similar
deformation properties at high temperature
Indirect extrusion
Billet Preparation
Design Principles applied
• Extrusion of composite billet results in 2 nested tubes when copper is chemically removed
Data/tables/design discussed
Fig. 4. Force–displacement diagrams with — FG: total force; indirect extrusion (right); FM: die force; direct extrusion (left); FR: friction force.
Fig. 5. Deformation resistance kW of NiTi as a function of the billet temperature TB.
Fig. 6. Specific extrusion pressure Pspec of NiTi in relation to the extrusion ratio ln V.
Fig. 7. Deformation resistance kWC of NiTi/CuCr versus core fraction Vcore of CuCr.
Fig. 9. Limits for indirect tube extrusion with a moving mandrel.
Other design consideration
Technical Advancement and industrial impact
• Innovative solution to shaping NiTi alloys