The strain-softening phenomenon of icosahedral Al-Pd-Mn single quasicrystals

For studying the strain-softening phenomenon of icosahedral Al-Pd-Mn single quasicrystals, compression tests with constant plastic strain rate were performed in the strain regime following the upper yield stress and combined with stress-relaxation experiments and temperature changes along the stress-strain curves at selected strains, it is found that both the strain-rate sensitivity and the temperature sensitivity of the flow stress decrease in the above strain regime with increasing strain. These results favour a model which assumes strain softening being caused by a change of the configuration of large cluster-like obstacles (e.g., the icosahedral clusters present in i-Al-Pd-Mn quasicrystals) by the moving dislocations thus reducing the stress needed to maintain the deformation. (C) 2000 Elsevier Science B.V. All rights reserved.