On the curious structural phases in Al-deficient (Al62Cu23Cr15) and Al-rich (Al68Cu17Cr15) quasicrystalline alloys

In the present work investigations on the effect of stoichiometric variations on the Occurrence and stabilization of quasicrystalline (qc) and related phases have been carried out. Based on the explorations of several Al-deficient and Al-rich versions of the ideal nominal composition i.e. Al₆₅Cu₂₀Cr₁₅, it has been found that the alloy compositions corresponding to Al₆₂Cu₂₃Cr₁₅ (Al-deficient) and Al₆₈Cu₁₇Cr₁₅ (Al-rich) exhibit several structural subtleties. The Al-deficient alloy, has been found to exhibit crystalline bcc and fcc phases with a = 8.90 Å and a = 17.98 Å respectively. In addition to these phases, a new crystalline bcc variant (a = 15.42 Å) originating from the bcc (a = 8.90 Å) phase has been found. Also a curious superstructure of the fcc (a = 17.98 Å) has been observed. The Al-rich alloy typified by Al₆₈Cu₁₇Cr₁₅, on the other hand, does not exhibit any structural variants, instead it shows nearly pure i-phase.