Design of potent grain refiners for wrought aluminium alloys

Al-B binary alloys cannot nucleate commercial purity aluminium, while Al-Ti binary alloys offer a modest grain refinement that relies only on the growth restriction capacity of Ti. The stoichiometric Al-Ti-B alloy, on the other hand, provides a fully equiaxed structure across the section of the cast sample with an average grain size under 200 mu m, endorsing the potency of the TiB2 particles. The grain refining efficiency is even better when the Ti concentration of the master alloy is in excess of the TiB2 stoichiometry. The excess Ti alloys that contain TiB2 and Al3Ti particles offer a remarkable grain refining capacity with an average grain size of similar to 100 mu m 5 min after inoculation. The grain refinement efficiency peaks at a Ti/B ratio of 4.3, producing an average grain size of 83 +/- 9 mu m.