Particle shape modification and related property improvements

The increasing sophistication of powder metallurgy processing, together with the greater demands on final product quality have led to an increased demand for metal powders of high quality. In this paper we report the successful preparation of two spheroidized metal powders, —electrolytic copper powder mixed with Al2O3 particles and hydrogenation–dehydrogenation (HDH) titanium powder — produced by high speed impact using a particle composite system (PCS). Experimental results show that irregularly shaped metal particles can be processed into spherical particles by use of this process. The spheroidizing process increases bulk density of Ti powder from 1.15 g/cm3 to 1.73 g/cm3 and its fluidity index from 46 to 71, improves surface morphology of either single Ti particles or composite Al2O3/Cu particles and molding properties of bulk powders. The characteristics of sintered parts made from spheroidized powders are superior to those of products made from the untreated irregular powders.

Irregular metal powder has poor flowability, which is deleterious for injecting, sintering and hot pressing. Spherical particles allow denser particle packing and give a smoother macroscopic surface. This means that during powder injection, feed made from the shape modified powder has a low viscosity, and needs a lower injection pressure, so the deformation of the injection samples will be reduced.Figure optionsDownload as PowerPoint slide