Effect of Al-5Ti-1B refiner content on the microstructure and mechanical properties of V-x(Al-5Ti-1B) alloys for hydrogen purification

Effect of Al-5Ti-1B refiner content on the microstructure and mechanical properties of V-x(Al-5Ti-1B) alloys manufactured by vacuum arc melting for hydrogen purification has been investigated in this work. Significant changes appeared in the grain morphology of V-xATB (x=2, 3, 4, 5) alloys with the Al-5Ti-1B (ATB) content increasing (2–5 wt%), while slender needle-like TiB phases were gradually precipitated inside the grains and increased in quantity, and grains were gradually refined. The precipitation of TiB phases in V-xATB alloys is advantageous for grain refining. Forming reasons of TiB phase and its morphology were discussed. The fracture mode for all five alloys is brittle fracture at room temperature. The combined strengthening effect of solid solution, fine-grained and precipitation of V-xATB alloys gradually improve with increasing ATB content, increasing the alloys' hardness and strength. The hardness and strength of the V-5ATB alloy are the highest, but the elongation is lower despite the fact that the grain size is the smallest among V-xATB alloys. This is because the extent of plasticity increase caused by grain refinement in the V-5ATB alloy is less than the extent of plasticity decrease caused by the strengthening of solid solution and hard-brittle TiB phase precipitation. This can be attributed to the significant reduction in plasticity caused by the solid solution and hard-brittle TiB phases precipitation of V-5ATB alloy. •Grain morphology of V-xATB alloys with ATB content increasing changed significantly.•ATB content increasing leads to TiB phases were gradually precipitated in V alloys.•Formation reason of TiB was furtherly judged by chemical and thermodynamic approach.•Grain size of the alloys reduces as ATB content increases due to refining role of TiB.