Microstructure, mechanical properties and hydrogen permeability of multiphase V-Ti-Ni alloy membranes

Abstract Multi-phase V-Ti-Ni alloys membranes consist of primary V-based solid solution (Vss) for hydrogen permeation and eutectic phases with high hydrogen embrittlement resistance. Different element content in the alloy results in the different microstructures, and their effects on mechanical properties and hydrogen permeability have been studied for the V-Ti-Ni alloys (V70Ti15Ni15 and V60Ti20Ni20) with equal Ni/Ti atom ratio. The increase of Ti and Ni content in the alloys leads to the rise of interdendritic phase (Ni-Ti compounds) volume fraction. The mechanical property testing shows the strength, hardness and plasticity of the alloys both increase with the increase of Ti and Ni, which refer to a larger combination effect of solid solution hardening and particle strengthening, and the volume fraction of NiTi phase in the alloy. Hydrogen permeability of V60Ti20Ni20 alloy membrane is 4.2 × 10−8 mol m-1s-1 Pa-0.5, which is more than twice that of Pd-25Ag alloy membrane at 673 K, and has better hydrogen embrittlement (HE) resistance. Increasing the proportion of NiTi phase is beneficial to improving the mechanical properties and HE resistance of the alloy membrane. The alloy membranes for hydrogen permeation with good comprehensive performance can be obtained by properly adjusting alloying element content and controlling phase composition.