IHCP-Based Estimation of the Transient Metal–Mold Interfacial Heat Transfer Coefficient in an Al-Cu-Mg Alloy: Correlations with Macro- and Microstructural Evolution and Hardness

Abstract The heat transfer coefficient at the metal–mold interface (h i ) is a key boundary parameter that controls solidification kinetics through its influence on heat extraction. Its estimation under transient conditions remains challenging due to the evolving nature of interfacial contact, while its influence on metallurgical aspects is not yet fully understood, especially for Al-Cu-Mg alloys. This limits the development of predictive heat transfer models for transient casting processes involving these alloys. The present study aims to estimate h i during solidification of an Al-3Cu-0.5Mg (wt.%) alloy and correlate h i with the columnar-to-equiaxed transition (CET), microstructural evolution, and microhardness. Transient heat transfer during horizontal solidification in a water-cooled stainless-steel mold was analyzed using a thermal resistance formulation along with a quasi-binary approximation and a finite difference scheme. The numerical temperature-time data obtained at different positions within the casting domain, combined with experimental thermal data reported in the literature, were used in an inverse heat conduction problem (IHCP) analysis to estimate h i by minimizing the deviation of the simulated cooling curves with respect to the experimental ones. The resulting h i evolution is described by a power-law relationship, h i = 7000(t) –0.15 , reflecting the progressive reduction in interfacial heat transfer during solidification. Based on metallographic data reported in the literature, the h i values corresponding to the onset and completion of the CET are identified. Furthermore, power-law relationships are proposed to describe the decreases in primary (λ 1 ) and secondary (λ 2 ) dendritic arm spacings, corresponding to approximately 70% and 57% reductions, respectively, with increasing h i . Finally, a power-law relationship relating the Vickers microhardness to h i is proposed. These results provide a quantitative basis for improving the prediction of thermal conditions in industrial manufacturing processes.