Study of martensitic stabilisation under stress in Cu–Al–Be shape memory alloy single crystal

✍ Scribed by C.H Gonzalez; C.J De Araújo; N.F Quadros; G Guénin; M Morin

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 336 KB
• Volume: 378
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2003.11.069

✦ Synopsis

Martensitic stabilisation phenomenon in the copper-based shape memory alloys has been invariably related to thermomechanical treatments and post-quench history. This phenomenon degrades shape memory properties and reduces their potential for industrial applications. In the present work, superelastic tests in a single crystal of Cu-Al-Be alloy were realised to study the martensitic stabilisation processes. Direct quenched samples have been studied in a special apparatus which allows to measure simultaneously stress-strain and electrical resistance. Two experimental procedures were used: superelastic cycles (8% strain) and ageing in mixed state. In the second test, the sample is submitted to a 4% strain by superelasticity which leads to a mixture of ␤-phase and single variants of martensite separated by parallel interfaces. After 24 h, the sample is strained up to 8% and finally the stress is removed leading to a total strain recovery. The stress-strain as well as the resistivity curves show a very different behaviour between the volume fraction which have been aged in the martensitic state and the one aged in the ␤-phase state. The results are discussed in terms of thermal treatment influence and stabilisation processes.