Ultrafine Grained Copper Electroforming Process Optimization

Bidirectional impulse electroforming super-fine grain copper experiment was conducted in this paper. the appearances and crystal dimension of electronic deposition layer formed under different parameters of electronic impulse was observed by TEM and SEM, and mechanism of the metal electroanalysis sediment process and crystallization was discussed.The results shows that super-fine grain cooper can be obtained by Bidirectional impulse electroforming. With the increase of positive current density , grain size decreased, and the crystal was fined; but if the i+ is excessive than a certain value, the grain size will get enlarged over again, and the deposition layer will be badly burned; and the increase of anode γ + will make the grain size grow gradually; and if the anode frequency f increased, the grain size will be smaller. Furthermore, cathode electronic impulse parameters also can affect appearances of the deposition layer and the grain size, although the impact is not as distinct as the positive one.The average grain size of super fine copper is about 450nm, and the strength is greatly improved, which is about two times as strong as the common coarse copper. The yield strength is as high as 546. 8MPa, while the tensile strength reaches 682.1MPa. It is that fined grain size and a large number of dislocation domain walls existing in sub-grain the main cause of strength increase. The intensity of electronic deposition layer with many twins falls, while the elongation increases. It is mainly because that dislocation slides easily within large twin crystal, which leads to the decrease of strength and the increase in plasticity. After the super fine copper was heat treated, grain size growing and quantity of twins decreasing was observed. As a result, the strength of the copper falls, and the elongation increases up to about 20%.