Mechanism of property enhancement of Cu−Ti alloys via microalloying with Cr and Mg elements

The effect of adding Cr and Mg on the microstructure and properties of Cu−Ti alloys was examined. Cu−Ti−Cr−Mg alloys were fabricated using vacuum induction melting. The microstructure and phase composition of Cu−Ti−Cr−Mg alloys in different aging states were characterized. Additionally, the hardness and electrical conductivity of the materials were investigated. Results show that the precipitation pattern in Cu−Ti−Cr−Mg alloys resembled that of binary Cu−Ti alloys, with Cr and Ti forming the intermetallic compound of Cr₂Ti during casting. The introduction of Cr and Mg increased the hardness of the alloy. Increasing the Mg content in the Cu−Ti−Cr−Mg alloy led to grain refinement and fast nucleation of continuous precipitates during the early aging stage. Moreover, the addition of Mg impeded discontinuous precipitate growth by segregating along the precipitate surfaces. Consequently, the Cu−4Ti−0.5Cr−1Mg alloy exhibited limited discontinuous precipitates at the grain boundaries and a gradual decline in hardness during the over-aging period.