Plastic Deformation of Fine-Grained Al--Cu--Fe--(B) Icosahedral Poly-Quasicrystals at Elevated Temperature

Fine-grained Al--Cu--Fe--(B) icosahedral poly-quasicrystals (IQCs) as the main materials and fine-grained Al--Pd--Mn IQCs as the supplements, both prepared by powder metallurgy, are uniaxially deformed at various temperatures and strain rates. The systematic study shows the dependences of curves of the true stress versus true strain on several parameters, such as temperature, strain rate and grain size. For Al--Cu--Fe IQCs with grain sizes of about 10--30μm, QC-specific intra-granular softening drop appears in the deformation curves at lower temperatures and/or faster strain rates, but disappears in those curves at higher temperatures and/or slower strain rates, which suggests that the inter-granular effects such as grain-boundary sliding
should be taken into account to interpret the continuous hardening, similarly to conventional poly-crystals. For Al--Cu--Fe-B IQCs with smaller grain sizes of about 1μm and fine-grained Al--Pd--Mn IQCs with grain sizes of about 10μm, QC-specific intra-granular softening drop is absent for all the deformation curves at the possible lowest temperature and fastest strain rate. This implies that the smaller the grain size, the more the inter-granular contribution. At the same time, due to the rapid recovery caused by intense diffusion in small-sized grains, the intra-granular quasicrystal lattice reorders rapidly from
disordering, which also inhibits the intra-granular softening drop to some extent.