Solidification of Metallic Alloys: Does the Structure of the Liquid Matter?

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 51; no. 6; pp. 2651 - 2664
• Main Authors: Rappaz, M., Jarry, Ph, Kurtuldu, G., Zollinger, J.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2020; Springer Nature B.V; Springer Verlag/ASM International
• Subjects: Aluminum base alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Diffusion; Engineering Sciences; Equilibrium conditions; Gold base alloys; Icosahedral phase; Materials; Materials Science; Metallic Materials; Metallurgical and Materials Transactions 50th Anniversary Collection; Metastable phases; Nanotechnology; Nucleation; Quasicrystals; Short range order; Solid solutions; Solidification; Structural Materials; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-020-05770-9

In 1952, Frank (Proc R Soc Lond Ser-Math Phys Sci 215:43–46, 1952) already postulated that Icosahedral Short Range Order (ISRO) of atoms in the liquid could possibly explain the large nucleation undercoolings measured in metallic alloys by Turnbull and Fisher (J Chem Phys 17:71–73, 1949). About thirty years later, this conjecture was proven to be key for the understanding of Quasicrystals (QC) formation (Shechtman et al. in Phys Rev Lett 53:20, 1951–3, 1984). More recently, it has been found that a few tens to thousand ppm of solute elements in Al-base and Au-base alloys can influence the nucleation and growth of the primary fcc phase via mechanisms involving ISRO and QC formation. ISRO has also been found to limit the mobility, and thus diffusion, of atoms in the liquid. This can lead to out-of-equilibrium conditions, e.g., the formation of metastable phases or supersaturated solid solution, at reduced velocity compared to alloys where ISRO is not predominantly present. Finally, there are several experimental evidences that ISRO is also responsible for twinned dendrites formation in Al alloys. The present contribution summarizes these recent findings and points out the implications that these might have in the field of solidification and additive manufacturing.