Modification of Hardness and Electrical Conductivity of Copper-Titanium Alloy by Energetic Electron Irradiation

We performed 1.5 MeV electron-irradiation at 333 K and 533 K for Cu-4.2 at% Ti alloy with a single phase of super-saturated solid solution, and investigated the irradiation-induced changes in Vickers hardness and electrical conductivity. With increasing the electron fluence, both of the hardness and the electrical conductivity increase. Such phenomena can be ascribed to the formation of Ti-rich precipitates that are caused by irradiation-enhanced diffusion of Ti atoms. The increase in electrical conductivity is caused by the reduction of Ti content in Cu matrix because of the formation of Ti-rich precipitates. The increase in hardness is also caused by Ti-rich precipitates that are effective obstacles against the motions of dislocations. We found a clear correlation between the irradiation-induced change in the hardness, Delta Hv and change in electrical resistivity, Delta rho, or that in electrical conductivity, Delta sigma, as Delta Hv proportional to root-Delta rho, or Delta Hv proportional to root Delta sigma/sigma, irrespective of irradiation temperatures. This correlation suggests that the precipitate-cutting mechanism governs the irradiation-induced increase in hardness; that is, 1.5 MeV electron-irradiation at relatively low temperatures of 333 K to 533 K should promote the nucleation of fine Ti-rich precipitates preferentially rather than the growth of them. The present result shows that energetic electron irradiation is a good tool to improve the mechanical and electrical properties of Cu-Ti alloys.