Application of Rotary Forging to Consolidation of Metal Powders

Abstract

The consolidation of metal powders using a nutation-spin rotary forging machine is a two stage process. An initial, uniaxial, compaction stage is followed by a rotary stage which introduces shear deformation into the compact. Fundamental appreciations have been gained of the geometric, mechanical, and materials aspects of each stage and the ways which they interact. Particle geometry plays an important role: optimum geometry seems to be needles with aspect ratios close to 60:1. Enforced adoption of split die techniques to cope with local compaction pressures of several gigapascals has opened a range of possibilities for part shapes which is wider than that normally limiting PM parts. Re-entrant features, lugs, and similar features can be produced. Flow of material to replicate such features is brought about by high local pressures and shear stresses. Differing combinations of side wall segments can be used in a bolster to generate a flexible manufacturing cell. Materials successfully consolidated range from aluminium to tool steels. When applied to Distaloy and Astaloy types of, powders, product properties after sintering have been shown to be comparable with those of hot powder forgings. PM/0563