Solute adsorption energy criterion for discovering effective grain refiners in high-Si Al–Si alloys

Abstract

Grain refinement is crucial for achieving a uniform fine microstructure and superior mechanical properties in aluminum alloys. While the Al–5Ti–1B grain refiner is effective for low-Si Al–Si alloys, its refining performance deteriorates in high-Si alloys due to “Si poisoning”. In this study, ab initio calculations reveal that interfacial Si adsorption destabilizes the Al₃Ti monolayer, thereby reducing its nucleation potency. Based on this mechanism, a solute adsorption energy criterion is proposed to identify alternative grain refiners with improved resistance to Si poisoning and effective refinement performance. By systematically screening transition metals in the 4th and 5th periods, V and Nb are identified as promising candidates. Their corresponding Al–V–B and Al–Nb–B refiners reduce the grain size of Al–10Si from 1033 μm to 264 μm and 217 μm, respectively. This work not only provides deeper insights into the atomic-scale nucleation mechanisms in high-Si Al alloys but also introduces a computationally guided framework for the rapid discovery of effective grain refiners with enhanced resistance to Si poisoning.