On the Role of Dilute Solute Additions on Growth Restriction in Binary Copper Alloys

Abstract

The effect of dilute solute additions on growth restriction in binary Cu alloys has been assessed at different degrees of superheat. Columnar grain length values from Northcott’s work (Northcott in J Inst Metals 62:101-136, 1938) for binary Cu alloys were plotted against the corresponding undercooling parameter (P), the reciprocal of the conventional (Qconv.) and true (Qtrue) growth restriction factor (Schmid-Fetzer and Kozlov in Acta Mater 59(15):6133-6144, 2011) values. It was found that there was no correlation between the columnar grain length values and P, 1/Qconv. and 1/Qtrue values for different solutes and cast at the same degree of superheat. Unlike P, Qconv., and Qtrue values, the heuristic growth restriction parameter (β) (Fan et al. in Acta Mater 152, 248-257, 2018) modeling framework in conjunction with the critical solute content (C*) for growth restriction fitted well to binary Cu alloys.

The Role of Dilute Solute Additions on Growth Restriction in Cu-, Al-, Mg- and Ti-Based Alloys

“…A 100% equiaxed grain structure was observed in casts with individual additions of 0.1 wt.% of P, Sb, Bi, S, Se and Te. Moreover, critical solute concentrations for individual solute additions of Al, V, Ni and Zn were determined to be greater than the solute addition of 0.1 wt.% at a ∆T of 0.5 K [19]. In this case, there was no growth restriction (β = 0) by the solute additions, as the solidification became partitionless.…”

“…In the first approximated β case, the heuristic growth restriction parameter β was calculated for each amount of solute present in the binary Cu, Al, Mg and Ti alloys studied in this investigation using the methodology originally described by Fan et al [10]. This procedure was also briefly described in our previous work [19]. Values of m and k for binary copper alloys were calculated and were reported in [22], from which β .…”

“…In the true β case, the evolution of the phase fractions of the liquid and the solid was calculated based on the Gulliver-Scheil cooling conditions for a temperature step of 0.01K using the software package Pandat (version 2021) [32]. Cooling was calculated from the thermodynamic databases available in the literature for binary Cu alloys as cited in our previous works [19,33] and an extension to binary Cu alloys with Ge, Pt, Li and Sc solute additions [34][35][36][37]. Cooling was calculated from the thermodynamic databases from CompuTherm [38] for binary Al-, Mg-and Ti-based alloys.…”

“…This procedure was also briefly described in our previous study on the role of dilute solute additions on growth restriction in binary copper alloys [19], in which the conceptual, heuristic growth restriction parameter (β) modelling framework [10] was applied. In binary alloys, values lower than a threshold of 10 at.% are generally classified as dilute alloys, while those greater than that are classified as concentrated binary alloys [20].…”