The training and re-training procedures for the two way memory effect and its degradation in a CuAlBe alloy

• Published in: Scripta materialia 1996-06, Vol.34 (12), p.1899-1904
• Main Authors: Zúñiga, H.Flores, Rios-Jara, D., Belkahla, S., Nika, V., Guénin, G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Martensitic transformations; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/1359-6462(96)00067-X

The beta phase of the Cu-Al-Be alloy, as other copper based alloys, presents a thermoelastic martensitic transformation. This transition ( beta - > beta ) is responsible of different special effects: the shape memory effect (SME), the superelasticity, and the two way memory effect (TWME). The TWME corresponds to the memorization of two shapes: the low temperature one in the martensitic state and the high temperature one in the austenitic state. The change between one shape to the other is performed by simple temperature change. The TWME is not inherent to the martensitic transformation, it must be induced by a thermomechanical treatment called training. Several studies of the training have been carried out on Cu-Zn-Al, and Cu-Al-Ni, which consider different ways of applying stresses and thermal cycling procedures. In the case of the TWME degradation by cycling in those alloys, some authors report a rapid decrease for the first 30 cycles and a light decrease for the next hundreds of cycles. Earlier works about the thermal stability of the TWME in Cu-Al-Be alloys showed a good behavior compared with Cu-Zn-Al. In the case of Cu-Zn-Al an activation energy of 1.21plus/minus0.03 eV was found for thermal degradation at different temperatures. The aim of this work is first to demonstrate the ability of Cu-Al-Be alloys to display a good TWME, then to study its thermal degradation, and finally to explore the possibility of re-training a TWME aged sample.