The temperature and strain-rate dependence of the flow stress of icosahedral AlPdMn single-quasicrystals

Investigation of Strain Softening of Icosahedral AlPdMn Single Quasicrystals

“…The softening regime finally changes at large strains into a regime with constant stress level, the plateau regime. While the strong temperature and strain-rate dependence of the maximum stress has been investigated in recent years in detail [23,24], only little is known about the softening phenomenon. It is the purpose of this paper to present new measurements on icosahedral AlPdMn single quasicrystals in the strain softening regime.…”

“…[24]). The shear strain-rate sensitivity (SRS) is determined by strain rate changes or by stress-relaxation experiments (SRE), respectively, the latter technique was applied here (see [39]).…”

“…Such a procedure has been used by Feuerbacher et al [23] and may be one of the reasons contributing to the discrepancy of the DH values determined by these authors in comparison with the values of Ref. [24]. As to the results of strain-rate changes a SRS of 33 MPa was found for the second strain rate change performed at e p 0X18.…”

Al–Pd–Mn icosahedral quasicrystal: deformation mechanisms in the brittle domain

“…This behaviour strongly suggests that diffusion plays an essential role in quasicrystal plasticity. Activation volumes, which were measured at high temperatures using different methods [7][8][9][10][11], have values too high to correspond to a deformation mechanism that would only imply diffusion. The stress-strain curves obtained at high temperatures for conventional deformation tests exhibit a yield point similar to the one observed in semi-conductors.…”

“…For Si and Ge, the origin of the yield point has been ascribed to a lack of mobile dislocations [12], while for Al-Cu-Fe poly-quasicrystals it has been attributed to a lack of dislocation mobility [13]. Cottrell-Stokes type experiments [14] performed on Al-Cu-Fe [15] and Al-Pd-Mn [16,17] quasicrystals show that the flow stress is almost fully reversible with deformation temperatures, indicating that the variation of the applied stress with temperature essentially reflects the variation of the effective stress.…”