Effect of vanadium element on the continuous precipitation behavior of Cu–3.2Ti–0.2Fe alloys

The effect of vanadium (V) element on the kinetics and mechanism of continuous precipitation in Cu–3.2Ti–0.2Fe alloys was elucidated using X-ray diffraction, high-resolution scanning transmission electron microscopy, calculation of precipitation activation energy and wavelength of spinodal decomposition. The results show the wavelength of spinodal decomposition decreased from 5.7 to 1.2 nm, and the corresponding activation energy increased from 41.7 to 119.5 J/mol with the addition of V element increased from 0 to 0.3 wt.%, performing severe inhibition on the continuous precipitation. Moreover, the hardness of the aged alloys was enhanced because of the refinement of V element on the precipitates, the Vickers hardness of the Cu–3.2Ti–0.2Fe–0.2 V alloy aged at 450 °C for 4 h was 38 HV 0.2 higher than that of alloy without V addition. Whereas the striking contrast of the phase boundary between part precipitates and Cu-matrix in the close-packed (111) plane and coherent boundary was observed in the HR-TEM images of alloys with V addition, the precipitation mechanism of counterpart was formed not via spinodal decomposition but based on the nucleation and growth mechanism within higher precipitate activation energy.