Formation of titanium hydride in dilute cuti alloy by aging in hydrogen atmosphere and its effects on electrical and mechanical properties*1

We have investigated the specific contributions of titanium-hydride precipitates to the improvement of electrical conductivity and strength for Cu0.36 mol% Ti alloys aged in a hydrogen atmosphere at 773 K, where Cu4Ti phase is not to appear. During the aging, titanium-hydride particles, which have a composition of H/Ti = 2, are formed by reaction of solute titanium with hydrogen diffused into the alloy. The particles have an octahedral shape with facets parallel to {111} of the matrix. The size and volume fraction of the hydride particles increase with aging time, and then level off after aging for 100 h, while the number density exhibits a maximum at 24 h. The precipitation reduces the concentration of solute titanium in the matrix and leads to significant improvement of the electrical conductivity, to the level comparable to pure copper. The dispersed TiH2 particles gives rise to strengthening with the Orowan mechanism, of approximately 40 MPa at a maximum in yield strength.