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

提出了一种以金属粉末为原料生产长棒材和长管材的挤压新工艺。在这个过程中，将少量粉末供应到容器中，然后在短行程中进行挤压，这是一个又一个重复的过程。作为模型材料，采用雾化铝粉，直接挤出，不装罐，不掺入任何粘合剂和润滑剂。(1)经证实，可以生产出相对密度为98- 99%、抗拉强度为80- 90%的固体铝棒材和管材，没有任何问题。粉末挤压的最佳半模角在30-40度左右，而固体金属挤压的最佳半模角在5-10度左右。(2)热挤压生产的棒材强度比冷粉末挤压生产的棒材强度稍大。然而，挤压棒的表面状况由于磨损的发生而不是很好。(3)结合Oyane和Shima提出的多孔材料塑性理论，采用平板法分析计算了轴向应力和密度分布。分析结果与实验结果吻合较好。(4)尝试用顺序粉末挤压法制备所谓的功能梯度材料，并对其可能性进行了探讨。

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.