Development of Sequential Powder Extrusion Process and Its application to Production of Functionally Gradient Materials

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A new extrusion process is proposed to facilitate the production of long rods and tubes by using metal powders as starting materials. In this process, the supply of small amount of powder into container and subsequent extrusion in short stroke is repeated one after another. As a model material, atomized aluminum powder is used and is directly extruded without canning and without blending with any binders and lubricants.(1) It is confirmed that rods and tubes with relative density of 98-99 % and tensile strength of 80-90 % of solid aluminium can be produced without any problems. The optimal semi-die angle for powder extrusion exists around 30-40 degree, while 5-10 degree for the extrusion of solid metals.(2) The strength of a rod produced by the hot extrusion is somewhat larger compared with that by the cold powder extrusion. However, the surface condition of extruded rods is not good due to the occurrence of galling.(3) The axial stress and density distributions are calculated by the analysis using slab method together with the plasticity theory of porous materials proposed by Oyane and Shima. The analytical results show good agreement with the experimental ones.(4) An attempt is made to produce so-called functionally gradient materials by the sequential powder extrusion, and the possibility is discussed.