One way to improve the mechanical properties of Al-Si alloys is to add chemical modifiers that affect the microstructure of the cast components. Small amounts of Sr cause the modification of the eutectic Si particles from a coarse plate-like morphology into a fine fibrous one. This study sets out to analyse the effects of chemical modification on an Al- 7%Si-0.3%Mg foundry alloy treated with Sr, ranging from 62 ppm to 820 ppm. Assessment of modification level was evaluated by both thermal analysis technique and quantitative microstructural investigations. Up to now, little attention has been paid to the role played by microstructural characteristics in modification level evaluation commonly performed by comparison with standard images. In the present investigation, numerical methods proposed in literature have been considered in an attempt to understand their effectiveness. Comparison between thermal analysis results and geometrical parameters of eutectic Si particles highlighted the impact of microstructural homogeneity on modification level evaluation. Another interesting finding regards the presence of Ca in Sr-based intermetallics investigated with SEM-EDS technique
