First-principles study for the enhancement of the stability of the precipitates in the Cu alloys

Cu is widely used as an electronic circuit component because of its high conductivity. However, in order to be used as connector materials, high strength as well as the high conductivity is required to maintain the desired shape. The Cu-Ti alloy is one of precipitation hardening alloys with the tensile strength of 800~1200MPa and the conductivity of 10~20%IACS. In general, the precipitation hardening alloys can be strengthened more by additional cold working after aging. However, we confirmed that these precipitates dissolve in Cu matrix during cold working, lowering the conductivity considerably. To obtain high conductivity and high strength simultaneously, it is essential to solve this problem. In this study, we tried to find a way to increase the stability of the precipitates in order to avoid dissolution of them during cold working. Using the density functional theory(DFT) calculations, we analyzed the characteristics of the precipitates in Cu-Ti alloy. To find additional elements to enhance the stability of the precipitates, we investigated the properties of them doped with 3d transition metals. Based on DFT results, we found a proper element stabilizing the precipitate and confirmed that the dissolution was inhibited after cold working in Cu-Ti alloys experimentally.