Effects of in situ formation of TiB2 particles on age hardening behavior of Cu-1wt% Ti-1wt% TiB2

Age hardenable Cu-1wt% Ti-1wt% TiB2 composite was produced by adding boron powder to Cu-Ti melt. TiB2 nano-particles were formed via in situ reaction between titanium and boron in the melt. This composite was aged in a temperature range of 300-550°C for a period of 1-25h. Then, the age hardening behavior of the composite was compared with that of the binary Cu-2wt% Ti alloy. The microstructure of the composite was examined with a high-resolution transmission electron microscope (HRTEM). The results of this study showed that TiB2 particles can act as a heterogeneous nucleation site for β'(Cu4Ti) precipitates. Substantial increase in tensile and yield stress of composite (i.e. 63% and 186% respectively) occurred relative to the solution state, after ageing at 450°C for 10h. The maximum strengthening of the composite was associated with precipitation of metastable Cu4Ti near the ultra hard TiB2 particles within the matrix. However, the results of this research show that the mechanical properties of aged composites are in good agreement with those of binary Cu-2wt% Ti alloy; the maximum values of the hardness and electrical conductivity of the composite (i.e. 258HV, 28% IACS) and the binary Cu-2wt% Ti alloy (i.e. 264HV, 17% IACS) were obtained when solution treated samples were aged at 450°C for 10h and 15h, respectively.