Effects of Ti addition on the mechanical properties and corrosion resistance of the Cr₂Nb laves phase

The ternary alloys of Cr₂Nb-XTi (X=5, 10, 15, at%) were prepared by vacuum non-consumable arc melting. The solidification microstructures of arc-melted alloy were investigated using optical microscope (OM), X-ray diffraction (XRD) as well as scanning electron microscope (SEM), and the effects of Ti addition on the mechanical properties and corrosion resistance of Laves-phase Cr₂Nb were also studied. The results show that the solidified microstructures of these ternary alloys are mainly composed of C15-Cr₂(Nb,Ti), α-(Ti,Nb) and β-(Nb,Ti). A metastable phase C14-Cr₂(Nb,Ti) is observed only in the top part of the arc-melted ingots of Cr₂Nb-5Ti and Cr₂Nb-10Ti alloys at low cooling rate. Meanwhile, with the increase in Ti content, the microhardness of Cr₂Nb-XTi alloy decreases gradually and the alloy fracture toughness increases continuously. As the Ti content reaches 15 at%, the fracture toughness of the alloy Cr₂Nb-15Ti could attain 3.1 MPa·m^1/2, twice of that of the single-phase Cr₂Nb. In addition, as the Ti content increases, the corrosion performance of the alloy Cr₂Nb-XTi declines, but the alloy Cr₂Nb-15Ti still exhibits well corrosion resistance.