Refining As-cast beta-Ti Grains Through ZrN Inoculation

The columnar-to-equiaxed transition and remarkable refinement of beta-Ti grains occur in an as-cast Ti-13Mo alloy when a new grain refiner, ZrN, was inoculated at a nitrogen level as low as 0.4 wt pct. The grain refining effect is attributed to in situ-formed TiN particles that provide active nucleation sites and solute Zr that promotes constitutional supercooling. Reproducible orientation relationships were identified between TiN nucleants and beta-Ti matrix, and well explained by the edge-to-edge matching model.