Investigation of strain softening of icosahedral AlPdMn single quasicrystals

Icosahedral AlPdMn single quasicrystals were deformed in compression with c onstant plastic strain rate in order to study the strain-softening phenomen on which is observed in the strain regime following the upper yield stress and which characterizes the shape of the stress-strain curves of quasicryst als. Stress-relaxation experiments and temperature changes were performed a long the stress-strain curves at selected strains. It is found that both th e strain-rate sensitivity and the temperature sensitivity of the stress dec rease in the above strain regime with increasing strain. Within the regime of constant stress following the strain softening regime at large strains b oth sensitivities remain constant. These results favour a model which assum es strain softening being caused by a change of the configuration of large cluster-like obstacles (e.g. the icosahedral clusters present in i-AlPdMn q uasicrystals) by the moving dislocations thus reducing the stress needed to maintain the deformation.