Effect of Al Content on Microstructure and Mechanical Properties of as-cast V-xAl Alloy for Hydrogen Separation Membrane

Abstract:

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 not only affects the hydrogen separation performance, but also affects the strength and plastic forming properties. A series of binary alloys of V-xAl(x=5, 10, 20, 30)were prepared by vacuum non-consumable arc melting. The effect of Al content on microstructure evolution and mechanical properties of as-cast V-xAl 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-xAl alloys is composed of V-based solid solution and Al₂O₃ particles. The addition of Al element results in grain refinement, and cause 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 is slightly reduced, but the tensile strength reaches a maximum of 236Mpa, which is 12% higher than pure V. This is attributed to the combined effect of both solid-solution hardening and precipitation strengthening. When the content of Al element reaches 10at.% or more, the Al₂O₃ particles coarsen, the tensile strength of the alloy decreases, the plasticity decreases sharply, and the alloy loses plasticity.

Key words:V-Al binary alloys; Al content; as-cast alloy microstructure; mechanical properties