In situ observation of pore evolution during melting and solidification of Al-Pd-Mn quasicrystals by synchrotron X-ray radiography

It is now generally admitted that pores are intriguing special features of quasicrystals. Therefore, we have performed an 'in situ' and real time observation of the pore evolution during directional solidi. cation and melting cycles of an icosahedral Al-Pd-Mn bi-grained sample, by synchrotron X-ray radiography. Rather surprisingly, no pore was observed to grow during the solidi. cation stages. Nucleation and growth of pores were first seen during melting. These pores were subsequently shrinking either just before being absorbed or during resumption of directional solidi. cation. It is concluded that the vacancy origin of pores is certainly valid whereas the vacancy supersaturation, needed thereby to explain their growth, would be more probably related to the peculiar structure of quasicrystal than to the destruction of the thermal equilibrium