Stabilization of icosahedral phase in Si substituted version of Al 65Cu 20Cr 15 alloy

Abstract

In order to find out the effect of Si on quasicrystalline (QC) and related phases, Si has been substituted in place of Al in Al–Cu–Cr system. In the present investigation, various alloys corresponding to Al 65− x Cu 20Cr 15Si x ( x=1, 3,5,7 and 10 ) composition have been synthesized and characterized. The investigations reveal that at 1 at.% of Si both QC and crystalline (b.c.c., a=8.90 A ̊ ) phases are present but after annealing, the alloy becomes QC. The alloys having 3 at.% of Si has been found to show the formation of icosahedral phase which exhibits high degree of disorder. At 7 at.% Si, the dissociation of the icosahedral phase commences. The dissociated phases have been found to be icosahedral and disordered diamond cubic phase ( a=7.87 A ̊ ). At the highest silicon concentration (10 at.%) another crystalline phase: primitive cubic phase ( a≈10.90 A ̊ ) results along with the icosahedral phase.