Effect of Al Content on Microstructure and Mechanical Properties of As-cast V-Alx Alloy

V-Al alloy membrane has good resistance to hydrogen embrittlement and high hydrogen permeability, which is expected to become a substitute material for replacing Pd alloy membrane in the future. The microstructure of V-Al alloy affects not only the hydrogen separation performance, but also the strength and plastic forming properties. A series of binary alloys of V-Alx (x=5, 10, 20, 30, at%) were prepared by vacuum non-consumable arc melting. The effect of Al content on microstructure evolution and mechanical properties of as-cast V-Alx alloy was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers hardness tester and tensile testing machine. The results show that the solidification microstructure of these V-Alx alloys is composed of V-based solid solution and Al2O3 particles. The addition of Al element results in grain refinement, and causes the reduction of grain size with the increase of the Al content. When the content of Al element is 5at%, the elongation of the alloy slightly reduces, but the tensile strength reaches a maximum of 236 MPa, which is 12% higher than that of pure V. This is attributed to the combined effect of both solid-solution hardening and precipitation strengthening. When the content of Al element reaches lOat% or more, the Al2O3 particles coarsen, the tensile strength of the alloy decreases, the elongation decreases sharply, and the alloy loses plasticity.