Equiaxed grain structure formation during directional solidification of a refined Al-20wt.%Cu alloy: In situ analysis of temperature gradient effects

•Directional solidifications of refined Al-20wt.%Cu alloys were carried out.•Microstructure formation was observed in situ and in real-time by X-radiography.•The impact of temperature gradient on the grain structure formation was investigated.•Temperature Gradient Zone Melting (TGZM) effect was evidenced.•Quantitative measurements of the grain characteristics were performed.