ON THE CURIOUS STRUCTURAL PHASES IN AL-DEFICIENT (AL62CU23CR15) AND AL-RICH (AL68CU17CR15) QUASI-CRYSTALLINE ALLOYS

In the present work investigations on the effect of stoichiometric var iations on the occurrence and stabilization of quasicrystalline (qc) a nd related phases have been carried out. Based on the explorations of several Al-deficient and Al-rich versions of the ideal nominal composi tion 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 b een found to exhibit crystalline bcc and fcc phases with alpha = 8.90 Angstrom and alpha = 17.98 Angstrom respectively. In addition to these phases, a new crystalline bcc variant (alpha = 15.42 Angstrom) origin ating from the bcc (alpha = 8.90 Angstrom) phase has been found. Also a curious superstructure of the fcc (alpha = 17.98 Angstrom) has been observed. The Al-rich alloy typified by Al68Cu17Cr15, on the other han d, does not exhibit any structural variants, instead it shows nearly p ure i-phase.