Observation of glide dislocations in D0(20) ordered Al3Ni

An Al-Al3Ni composite has been prepared by centrifugal casting to contain a large volume fraction of D0(20) Ordered Al3Ni. The Al3Ni phase embedded in the Al matrix is found to satisfy an orientation relationship given by (100)(D020)//((1) over bar 31)(fcc), [010](D020)//[101](fcc), where orthorhombic D020 takes a rod shape with the longitudinal axis along the [010](D020). It has been revealed that Al3Ni is deformable by dislocati on glide;at 300 K when Al3Ni embedded in a thin foil specimen is deformed b y compression. The Burgers vector and slip plane of the glide dislocations have been determined as [110](1(1) over bar 0) perfect superdislocations by examining visibility and g.b values under a high-voltage electron microsco pe. Four of these perfect dislocations are found to move as a group, with a ccompanying residual contrasts between them. For the orientation relationsh ip given above, the shear direction and plane are found to be nearly contin uous across the interface between Al3Ni and the Al matrix, suggesting that penetration of the shear deformation through the Al-Al3Ni interface plays a n important role in the generation of mobile superdislocations.