On the variation of mechanical properties with solute content in Cu-Ti alloys

The variation of mechanical properties and electrical conductivity of Cu-Ti alloys of four compositions, viz. Cu-1.5 wt%Ti, Cu-2.7 wt%Ti, Cu-4.5 wt%Ti, and Cu-5.4 wt%Ti, have been studied in solution treated (ST), solution treated + peak aged (ST + PA), and solution treated + cold worked + peak aged (ST + CW + PA) conditions. Tn the ST condition, Ti is found to be a potential solid solution strengthener of copper showing greater effect than other elements like Zn, Ni, Al, Si, Be, and Sn. Solid solution strengthening in Cu-Ti alloys is attributed to the interaction of titanium atoms with screw dislocations and the effective interaction is more due to modulus mismatch than size misfit. Further, a marked change in the linear variation of tensile strength and elongation with Ti content is observed at about 4.0 wt%Ti beyond which, tensile strength increases sharply while elongation decreases further, which is attributed to fine scale precipitation formed during quenching of Cu-4.5 Ti and Cu-5.4 Ti alloys. On the other hand, hardness and tensile properties increase linearly up to 5.4 wt%Ti in the peak aged condition with or without prior cold work, due to uniform precipitation of Cu4Ti, beta(1) phase in all the four alloys. The increase in yield and tensile strengths due to solid solution strengthening, cold work, and precipitation have been determined quantitatively in ST + CW + PA alloys. While electrical conductivity is less, the mechanical properties of Cu-Ti alloys are comparable with those of commercial Cu-Be alloys. (C) 1999 Elsevier Science S.A. All rights reserved.