Extrusion of nickeltitanium alloys Nitinol to hollow shapes

Extrusion of nickel–titanium alloys Nitinol to hollow shapes Author: K. Müller Presenter: Joshua Furner Date: 16 September 2009

Function of Paper • Describe results of hot extrusion of Ni. Ti alloys • Development of extrusion principles for Ni. Ti 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 formgedächtniselementen 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 Ni. Ti-Legierungen. Metall. 52 (1998), p. 12. 6. K. Mueller, Grundlagen des Strangpressens, Expert Verlag Renningen Malmsheim, 1995. ISBN 38169 -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 Ni. Ti and steel results in welding • Cu canning of Ni. Ti 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 k. W of Ni. Ti as a function of the billet temperature TB.

Fig. 6. Specific extrusion pressure Pspec of Ni. Ti in relation to the extrusion ratio ln V.

Fig. 7. Deformation resistance k. WC of Ni. Ti/Cu. Cr versus core fraction Vcore of Cu. Cr.

Fig. 9. Limits for indirect tube extrusion with a moving mandrel.

Other design consideration

Technical Advancement and industrial impact • Innovative solution to shaping Ni. Ti alloys