Detection of shock-wave-induced internal stresses in Cu-Al-Ni shape memory alloy by means of acoustic technique

A response of materials, exhibiting the thermoelastic martensitic transformation (TMT), on the applied mechanical stress leads to the superplasticity, plasticity of the martensitic phase, shape memory effect, high damping capacity. Acoustic technique was used to detect the structural changes induced by shock-wave loading of Cu-Al-Ni crystals. The same acoustic method provides an estimate of the upper time limit to induce the TMT and plastic deformation of the martensitic phase.status: publishe

Influence of high-energy impact actions on the elastic and anelastic properties of martensitic Cu-Al-Ni crystals

The influence of high-energy impact shock-wave loading on the microplasticity and macroscopic performance of the Cu-AI-Ni crystals in the beta(1)' martensitic phase has been studied. Elastic and anelastic properties of quenched and aged polyvariant single crystals before and after impact shock-wave loading were measured in the temperature range 80-300 K, at a frequency of about 100 kHz in the strain amplitude-independent and amplitude-dependent ranges by means of the composite oscillator technique, and in the MHz frequency range using the pulse-echo technique. High-velocity impact loading of the specimens was realised by plane shock-waves with stress pulses with a duration of similar to 2 . 10(-6) s and stress amplitudes up to 5 GPa. A pronounced influence of impact shock-wave loading on the elastic and anelastic properties of the beta(1)' martensite has been observed. A strongly marked softening of the material and an enhancement of damping properties are revealed up to the highest stress pulse amplitudes. This behaviour differs fundamentally from the one observed in 'ordinary' fcc metals. Changes of the defect structure induced by shock-wave loading, which may be responsible for the observed phenomena, have been discussed. (C) 2000 Published by Elsevier Science S.A.status: publishe