DEFORMATION CONSOLIDATION OF METAL POWDERS CONTAINING STEEL INCLUSIONS

Uniaxial consolidation experiments have been conducted at room temperature for two deformable metal powders (1100 Al and Pb5% Sb) containing various amounts of spherical steel inclusions. The experiments illustrate that the inclusion phase offers little constraint to matrix deformation at volume fractions < 0.20, but produces a rapidly increasing constraint at larger volume fractions. Two constraining mechanisms have been identified through microstructural observations: (1) the matrix must be deformed more within the composite because of the excluded volume associated with the packing of particles and inclusions of different sizes, and (2) the inclusions from a continuous touching network (predicted with site percolation theory and direct observations of deformation flats on the steel spheres) which supports a portion of the applied stress and thus, partially "shields" the deformable phase from the total applied consolidation pressure. An analysis is presented to separate the contributions of each mechanism and shows that both mechanisms contribute comparable amounts to the constraint of matrix consolidation. It is suggested that because the inclusion network supports a significant portion of the applied pressure and releases its elastic strain in a non-linear manner (as described by Hertzian theory), the matrix is placed in tension when the applied pressure is released after consolidation.