Compaction behavior of rapidly solidified Al-Si-Fe-Cr alloy powders

摘要

Recently, the powder forging process of rapidly solidified Al alloys was investigated in order to de velop an inexpensive alternative process to produce high strength parts with complex shapes (1,2). It has been shown that the mechanical properties of powder-forged parts are as good as those produced by extrusion. Additionally, since powder forging produces a part in its final form directly from starting powders, without machining being necessary (near net shaping), the yield is high and less expensive in comparison with powder extrusion. Generally, it is necessary for powder consolidation to be performed by solid-phase diffusion at temperatures for below the melting points of the raw material powders, to ensure that the structural features obtained through rapid solidification are not lost. However, the surfaces of Al alloy powder are usually covered by an oxide layer approximately 10 nm thick. Unless this oxide film is ruptured and the fresh powder particle surfaces are allowed to come into contact with each other, it is not possible to obtain good bonding by diffusion. Therefore, the powder particles should be bonded together by plastic deformation during powder compaction step as well as forging stepi and so understanding the deformation and compaction behaviors are very important to achieve good, quality parts. Many attempts have been made to describe the compaction behavior of powders by mathematical models (3,4) and experimental results (5). However, these results are limited to the pressure-density relationship for special powders or pressure ranges, ignoring the particle characteristics, such as shape arid size.