Influence of pouring and mold temperatures on microstructural behavior and microhardness of the Al-4.5Cu-0.5(Al-5Ti-1B) alloy obtained by unsteady-state directional solidification: An experimental comparative study

Abstract

The microstructure of aluminum alloys, which is critical to their mechanical performance, is strongly influenced by the solidification conditions. This study evaluates the impact of pouring temperature (T_P) and mold temperature (T_M) on the microstructure, porosity, and solute segregation in the radial solidification of Al-4.5Cu-0.5(Al-5Ti-1B) alloy. Experimental analysis of 12 radially solidified ingots under varying T_P and T_M conditions revealed that lower T_P and T_M values produce a refined dendritic structure, with reduced primary dendritic arm spacing (λ₁) and decreased levels of porosity and shrinkage defects. Conversely, elevated T_P and T_M increase solidification time, leading to coarser grains, greater porosity, and enhanced interdendritic spacing. Notably, the radial solidification process also exhibited inverse segregation, with Cu concentration decreasing from the metal/mold interface toward the center. Microhardness measurements corroborated these findings, showing reduced hardness from the interface to the center due to lower Cu concentration and increased λ₁. The study's results provide essential insights into the thermal management of radial solidification in unsteady-state conditions, with practical implications for controlling microstructure and porosity in Al-Cu alloys and offer a foundation for validating numerical models for cylindrical radial solidification, a configuration not extensively explored in existing literature.