Preparation of Nanocrystalline Pure Copper by Multi-Directional Compression

The pure copper was deformed by multi-directional compression.The microstructure of pure copper was observed by OM and TEM, and the rule of microstructure evolution was analyzed.The hardness, conductivity and true stress-strain relationship of the deformed copper were characterized, and the changing trend of properties was summarized.The results show that with the increase of the cumulative strain of multi-directional compression, the grains of pure copper are intertwined with each other, the straight grain boundary is bent, the color difference between grains disappears, the microstructure is refined continuously, a wide fine grain area is formed at the original grain boundary, and when the cumulative strain reaches Σ12.8, about 100 nm grains transformed from sub crystals are formed in the structure; the hardness of pure copper increases with the increase of the cumulative strain of multi-directional compression, and the conductivity decreases with the increase of the cumulative strain of multi-directional compression,the hardness reaches twice than that of soft pure copper, and the conductivity remains high.The true stress-strue train curve also reflects the strengthening effect of multi-directional compression on pure copper.