Deformation behaviour of dispersion hardened nanocrystalline copper (original) (raw)

AbstrAct Purpose: The aim of this work was to describe deformation behaviour of nanocrystalline copper dispersionhardened with nanoparticles of tungsten carbide and yttria. Design/methodology/approach: Tests were made with the Cu, Cu-WC and Cu-Y 2 O 3 micro-composites containing up to 3 % of a hardening phase. These were obtained by powder metallurgy techniques, i.e. milling the input powders in the planetary ball mills, compacting and sintering. The mechanical properties (hardness, 0,2 YS, elongation during compression test) and microstructure were examined by the optical, scanning and transmission electron microscopy. Findings: Analysis of the initial nanocrystalline structure of these materials was made, and its evolution during deformation process was investigated with an account of the hardening effect and the changes in the mechanical and plastic properties. Results of this analysis have been discussed based on the existing theories related to hardening of nanocrystalline materials. Research limitations/implications: The powder metallurgy techniques make it possible to obtain copper-based bulk materials by means of milling input powders in the planetary ball, followed by compacting and sintering. Additional operations of hot extrusion are also often used. There is some threat, however, that during hightemperature processing or using these materials at elevated or high temperatures this nanometric structure may become unstable. The studies have shown the importance of "flows" in the consolidated materials such as pores or regions of poor powder particles joining which significantly deteriorate mechanical properties of compacted and sintered powder micro composites. Practical implications: A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with nanometric grain size of a copper matrix, which exhibit higher mechanical properties than microcrystalline copper. Originality/value: The paper contributes to the elucidation of deformation behaviour of high-porosity nanocrystalline copper dispersion hardened with tungsten carbide and yttria.