Microstructure and mechanical properties of Cu–3 at.% Ti alloy aged in a hydrogen atmosphere

The microstructure of Cu–3 at.% Ti alloy aged at 773 K in a hydrogen atmosphere of 0.37 MPa has been investigated, together with hardness and tensile strength. At the early stage of aging, needle-shaped α-Cu4Ti particles precipitate finely in a similar manner to the case of conventional vacuum-aging. On further aging, some α-Cu4Ti precipitates are extended, while others are replaced by δ-TiH2 precipitates. The precipitation of titanium hydride reduces the concentration of Ti in the matrix more efficiently than aging in a vacuum. The yield strength first rises, but falls on further aging. This is due to the microstructural evolution: α-Cu4Ti particles first form and grow, but then diminish because of the formation of titanium hydrides. Elongation to fracture, as well as the electrical conductivity, is promoted by long-time aging in the hydrogen atmosphere, reflecting the reduced Ti concentration in the matrix.