Mechanical behaviour and deformation mechanisms of Ni-Ti shape memory alloys in tension

¹ Domaine Mécanique, LG2mS, UPRESA 6066, Université de Technologie de Compiègne, BP 20-529, 60205 Compiègne Cedex, France
² GSM/LASMIS, Université de Technologie de Troyes, BP 2060, 10010 Troyes Cedex, France

Corresponding author: clervie.guillemer-neel@utc.fr

Received: 20 October 1999
Revised: 4 February 2000
Accepted: 10 February 2000
Published online: 15 May 2000

Abstract

We investigated the behaviour in tension and at room temperature of TiNi shape memory alloys in martensitic state. Our first experimental results show that two deformation mechanisms are involved in the behaviour of such materials: martensite platelets reorientation and irreversible plasticity. Moreover when irreversible plasticity appears, we observe an increase in the martensite to austenite transformation temperatures. The present study is especially focused on the deformation mechanisms and intends to identify the nature of the irreversible phenomena. It is shown that the reorientation process and the appearance of interface dislocations are in perfect agreement with a kinematic hardening. Finally a two loading surface model is proposed which allows not only to account for the overall behaviour but also to predict the transformation temperatures under an internal and/or external stress field.