Solidification Front Velocity of Ternary Titanium-Aluminides

Abstract

Ternary titanium-aluminides with compositions of Ti₅₁Al₄₇Fe₂, Ti₅₁A1₄₇Cr₂ and Ti₅₁Al₄₇Mn₂ were investigated with respect to the correlation of their solidification front velocity v and bulk undercooling ΔT. The observation of the solidification front during the recalescence event has been realized using a high speed video system capable of recording up to 12,000 pictures per second. The temperature measurement was carried out by pyrometry, avoiding contact with the sample. The comparison of the experimental data with the LKT-theory (Lipton, Kurz, Trivedi; [1]) refers to a primary (hcp) β-Ti solidification for undercoolings below ΔT≈ 130 K and primary (bcc) α-Ti solidification for ΔT≥ 130 K. For undercoolings ≥ 150 K the theory differs greatly from the experimental results.

The maximum undercoolings achieved were 268 K (Ti₅₁Al₄₇Fe₂), 285 K (Ti₅₁Al₄₇Cr₂) and 280 K (Ti₅₁Al₄₇Mn₂), corresponding to a solidification front velocity v ≈ 9-10 m/s for all alloys.