Calculating Ti-6Al-4V β Transus Through a Chemistry-Based Equation Derived from Combined Element Binary Phase Diagrams

A mathematical model was developed to correlate the relationship between titanium alloying elements (Al, O, N, C, V, and Fe) in Ti-6Al-4V, and the resulting beta transus temperature (β_t). The model was produced by analyzing the slope of the lines separating the alpha + beta (α + β) and beta (β) phase fields on combined element binary phase diagrams generated through the Pandat modeling software. Experimental results showed a strong agreement between the baseline data, obtained through differential thermal analysis (DTA), and the calculated β_t, determined by measuring the chemistry at a location adjacent to the DTA sample. The difference between the calculated β_t and the baseline DTA data was approximately ± 10 °F (± 5.56 °C). The thermodynamically ideal β_t temperature was additionally modeled for each set of chemistries through the Pandat software. These results were compared to the β_t temperatures determined through the chemistry-based equation and DTA methods.