나노 구리-니켈 혼합분말의 충격압축법을 통한 복합벌크재의 제조 및 특성평가

Abstract

Abstract In this study, nanocrystalline Cu-Ni bulk materials with various compositions were cold compacted by ashock compaction method using a single-stage gas gun system. Since the oxide layers on powder surface disturbs bond-ing between powder particles during the shock compaction process, each nanopowder was hydrogen-reduced to removethe oxide layers. X-ray peak analysis shows that hydrogen reduction successfully removed the oxide layers from thenano powders. For the shock compaction process, mixed powder samples with various compositions were preparedusing a roller mixer. After the shock compaction process, the density of specimens increased up to 95% of the relativedensity. Longitudinal cross-sections of the shock compacted specimen demonstrates that a boundary between two pow-ders are clearly distinguished and agglomerated powder particles remained in the compacted bulk. Internal crack tendedto decrease with an increase in volumetric ratio of nano Cu powders in compacted bulk, showing that nano Cu powdershas a higher coherency than nano Ni powders. On the other hand, hardness results are dominated by volume fraction ofthe nano Ni powder. The crystalline size of the shock compacted bulk materials was greatly reduced from the initialpowder crystalline size since the shock wave severely deformed the powders.Keywords: Nanocrystalline metallic powder, Gas gun system, Shock compaction