J. Phys. IV France 112 (2003) 471
DOI: 10.1051/jp4:2003927

Vacancies and the martensitic transition in Cu-based shape-memory alloys. A comparative study

R. Romero¹, A. Somoza¹, LI. Manosa² and A. Planes<sup>2

1</sup>  IFIMAT, Universidad del Centro de la Provincia de Buenos Aires and Comision de Investigaciones Cientificas de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil, Argentina
²  Departament d'Estructura i Constituents de la Matèria, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Catalonia, Spain

Abstract
The influence of vacancies on the properties of the martensitic transition on Cu-Zn-A1, Cu-A1-Be and Cu-A1-Mn shape-memory alloys has been studied. Positron annihilation spectroscopy and calorimetric measurements were performed after a quench from T , which ranged from room temperature to approximately 1100 K. In the three studied alloys, the retained vacancy concentration (C ) as a function of T shows a maximum at an intermediate temperature just after quenching. However, the room temperature post-quench evolution of C is different for the three systems. Furthermore, the relationship between the vacancy concentration and the transition temperature is characteristic for each alloy system: good correlation exists between both quantities in Cu-A1-Be, an indirect effect through ordering explains the observed behaviour in Cu-Zn-A1, while no correlation was found in Cu-A1-Mn.

© EDP Sciences 2003