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In general, plastic deformation of ordered alloys can reduce the degree of long-range order. This phenomenon has been observed in Ni[sub 3]Al. It has been shown that during mechanical milling of this alloy, the long range order parameter decreases with increasing milling time, but no detailed examination of the mechanisms by which plastic deformation brings disordering has been carried out. Earlier studies on ordered compounds such as Cu[sub 3]Au and Ni[sub 3]Al also showed that cold work or shock loading could create disordering in the ordered materials. The question of how deformation disturbs the ordered structure is also of importance since, a priori, superdislocations should not create disorder. It has been shown that intense deformation by superdislocations, as occurs inside a shear band, can actually lead to some disordering. Hence, the investigation reported here was concerned with the effect of deformation by cold rolling on the state of order of a well ordered Fe[sub 3]Al alloy containing some Cr. Particular attention has concentrated on the mechanisms by which the movement of dislocations affects the ordering. Iron aluminide (Fe[sub 3]Al) possesses a DO[sub 3] type ordered structure, and deformation should most likely be accomplished by the movement of four coupled (1/4)a[submore » 0] partial dislocations, a[sub 0] being the DO[sub 3] lattice parameter. The APB between the first two (1/4)a[sub 0] dislocations involves wrong nearest neighbors and can be noted as a B2 type fault. On the other hand, the APB between the two pairs of coupled (1/4)a[sub 0] dislocations involves only wrong second nearest neighbors and can be described as a DO[sub 3] type fault characterized by either a (1/2)a[sub 0] or a (1/2)a[sub 0] fault vector.« less |
