Fifth European Symposium on Martensitic Transformations and Shape Memory Alloys

J. Phys. IV France 11 (2001) Pr8-173-Pr8-178
DOI: 10.1051/jp4:2001830

Transformation temperatures, elastic and anelastic properties of Cu-Al-Ni crystals subjected to impact loading

S. Golyandin¹, S. Kustov^{1, 2}, S. Nikanorov¹, K. Sapozhnikov¹, A. Sinani¹, J. Van Humbeeck³, R. Schaller⁴ and R. De Batist<sup>5

1</sup>  A.F. Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg, Russia
²  LMPM, ENSMA, BP. 109, Chasseneuil-du-Poitou, 86960 Futuroscope, France
³  Katholieke Universiteit Leuven, Departement MTM, De Croylaan 2, 3001 Heverlee, Belgium
⁴  Institut Génie Atomique, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
⁵  University of Antwerpen, RUCA, IMS, Middelheimlaan 1, 2020 Antwerpen, Belgium

Abstract
Experimental investigations of the influence of impact loading on properties of Cu-Al-Ni single crystals have been performed. Crystals in the β phase were impacted with pulses of a uniaxial plane strain wave with a duration of about 2.10^-6 s. A normal component of stress in the direction of the pulse propagation ranged from 0.5 to 5.4 GPa. For as-quenched and impacted crystals martensitic transformation temperatures were determined, the Young's modulus (YM), strain amplitude-independent and strain amplitude-dependent internal friction were measured at a frequency of about 100 kHz over the temperature range of 300-90 K for strain amplitudes of 10^-7-2x10^-4. Experimental results indicate that β₁ → γ'₁ martensitic transformation (MT) and plastic deformation of the martensite are induced by the impact. The impact loading generates a "structure memory effect" : the YM in the austenite is not sensitive to the impact, but the consequent temperature-induced MT reveals a dramatic influence of the impact on the YM of the β₁ → γ'₁ martensite. The conclusion is drawn that the observed effect is fundamentally similar to the two-way memory effect, but is extremely sensitive to the impact stress. The origin of this phenomenon is attributed to the internal stresses, created by impact, which control the nucleation of preferentially oriented anisotropic martensitic variants during temperature-induced MT in impacted crystals. No influence of the impact loading on the transformation temperatures was detected for β₁ → γ'₁ MT, in contrast to elastic properties of the martensitic phase, indicating that structural changes due to the high-velocity impact do not affect appreciably the thermoelastic equilibrium and hysteretic motion of parent - martensite boundaries during the MT.

© EDP Sciences 2001