ROLE OF PLASTIC DEFORMATION IN METAL POWDER COMPACTION.

Results of mechanical testing, metallographic examinations and X-ray diffraction analyses of some atomized iron powder compacts are presented, together with a metallographic examination of compacted spherical superalloy powders. From these it is concluded that extensive plastic deformation occurs even during the first stage of compaction, but is not solely responsible for consolidation. Consolidation is seen as a result of a combination of mechanical interlocking and associated frictional welding created by surface shear deformation resulting from asymmetric loading. Thus it is difficult to achieve consolidation in spherical powders even after considerable plastic deformation. The transition from stage 1 to stage 2 compaction occurs when the compaction pressure exceeds the current bulk yield stress of the material, i. e. when plastic flow becomes homogeneous instead of local.