Effect of vanadium element on the microstructure and mechanical properties of Cu-3.2Ti-0.2Fe alloys

The second-phase particles play a critical role in refining microstructure and promoting properties in ultra-high strength Cu-Ti alloys. In this study, we researched the effect of adding 0-0.3 wt% vanadium (V) element on the Laves phase of Fe2Ti and the resulting variation of microstructures and properties in Cu-3.2Ti-0.2Fe alloys using first-principle calculations, in-situ transmission electron microscopy (TEM) and mechanical tests. The firstprinciple calculation results showed that the combination energy and formation enthalpy of Laves phase were affected by the V element, with the (Fe4,V4)Ti4 having the most stable structure and the lowest combination energy of -529.14 kJ mol- 1.atom- 1. Furthermore, the face-centered-cubic (FCC) or amorphous crystal structured boundary layer of Laves phase was coherent with the Cu-matrix when 0.2 wt% V was added to the alloys, acting as a more effective refiner of heterogeneous nucleation during the casting process. In-situ heated TEM evidenced that the Laves phase acted as an inhibitor of dislocation motion and grain boundary migration during the annealing process after cold-deformation. After annealing at 800 degrees C for 3 min and aging at 400 degrees C for 2 h and then at 450 degrees C for 4 h, Cu-3.2Ti-0.2Fe-0.2 V alloy possessed the ultimate tensile strength of 976.8 MPa and elongation of 18.8%, exhibiting high strength and good ductility.