Relation of various GFA indicators to the critical diameter of Zr-based BMGs

• We performed wedge test on four Zr-based BMGs to determine their critical diameters.
• We determined their characteristic temperatures to calculate several GFA indicators.
• We built plots for each GFA indicator vs. critical diameters with logarithmic fitting.
• We calculated R2 correlation coefficient and indicated the best GFA indicators.

In the face of a large number of glass forming ability (GFA) thermal indicators that can be found in the literature, the authors have made an attempt to order a variety of them by their correlation with the critical diameters (Dc) of four various Zr-based alloys. Dcs were determined by the wedge test and varied from 4.5 to 10.4 mm. Characteristic temperatures, determined by the DTA, were used to calculate some GFA thermal indicators: ΔTxg, Trg, Kgl, α, β1, β2, γ, γm, δ and ξ. The data were used to built plots: GFA indicator versus Dc. Using the logarithmic fitting, the R2 correlation coefficient was determined for each indicator. Ordering the GFA indicators by the R2 ascending values allowed both qualitative as well as quantitative comparisons. It was revealed that the ΔTxg indicator exhibited weak correlation (R2 = 0.019) with the Dc in contrast to β1, γ, γm and ξ. It was also proven that the solidus temperature should not be used in a formula of a GFA indicator in order to achieve high correlation with the Dc.The authors also made an attempt to modify the formula of the γm indicator in order to improve the R2 value. It was possible to raise it to the level of 0.882 – a new GFA indicator ω was proposed.