EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In this study, rapid solidification of single micro-sized AlSi12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry (DFSC), employing cooling rates from 100 K/s to 90,000 K/s. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The present study is relevant for the cooling rate, the nucleation behaviour, and the microstructure during rapid solidification of fine metallic powder-particles used in additive manufacturing. This work not only proposes a new approach to rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials.