Cyclic Deformation and Development of Dislocation Structures in a Centrifugally Cast Al–Al3Ti of Functionally Graded Material

Abstract

An Al-Al 3 Ti composite has been prepared to contain a large volume fraction of D02 2O ordered Al 3 Ti phase on one side and a smaller volume fraction on the other side by a functional grading process. The cyclic stress-strain curves obtained by strain control tests are compared with the available data on Al to delineate the effects of the Al 3 Ti plates distributed with concentration gradient. Examination of the crack nucleation and growth by a replica method has revealed that introduction of the non-deformable Al 3 Ti accelerates crack nucleation but concurrently hinders the spontaneous propagation in the cyclic tests. Observation of the final structure by HVEM has further revealed that presence of the non-deformable Al 3 Ti induces non-uniform distribution of dislocations near the Al 3 Ti plate, causing build-up of stress inhomogeneity, especially on the Al 3 Ti rich side. On the basis of these observations, utility of the FGM specimens is discussed with a particular interest in the lifetime prediction under cyclic loading.