Orthorhombic approximant phases and their relation to quasicrystals in mechanically alloyed Al–Cu–Fe–Si alloys

A new orthorhombic approximant of the icosahedral Al–Cu–Fe quasicrystal

“…This orthorhombic phase was also found as a secondary phase co-existing with the i-phase in Al-Cu-Fe-Si alloys prepared by mechanical alloying and annealing [16]. The same study also reported the existence of a closely related orthorhombic phase with a ¼ c ¼ 1.24 nm and b ¼ 4.77 nm [16]. It was further noticed that the a and c parameters of both orthorhombic phases are close to the lattice parameter a 1/1 of the cubic approximant [17] and that their b parameter is close to either 3a 1/1 or 4a 1/1 , suggesting that these orthorhombic phases could be described as a superstructure of the cubic phase but for small local rearrangements breaking the cubic symmetry [16].…”

“…Extensive studies of this region of the ternary phase diagram have been reported [3][4][5][6][7][8][9][10][11][12], notably by Quiquandon et al [12], showing that these approximants form along a line of constant electron per atom ratio e [16]. This orthorhombic phase was also found as a secondary phase co-existing with the i-phase in Al-Cu-Fe-Si alloys prepared by mechanical alloying and annealing [16]. The same study also reported the existence of a closely related orthorhombic phase with a ¼ c ¼ 1.24 nm and b ¼ 4.77 nm [16].…”