5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

The present contribution reviews the recent progress related to the influence of Icosahedral Short-Range Order (ISRO) and icosahedral Quasicrystals (i-QC) formation on the solidification of fcc alloys through minor solute element additions. From intensive crystallographic analysis of multi-twinned regions in as-cast Al-based and Au-based fcc alloys, Kurtuldu et al. have shown recently that a so-called “iQC-mediated” nucleation mechanism occurs when a few hundred ppm of Cr and Ir, respectively, are added to the melt [1] [2]. Similarly, it appears that the growth directions of dendrites in Al-Zn:Cr is also influenced by ISRO in the liquid, thus showing an attachment kinetics effect [3]. In a recent contribution, we have shown that iQC-mediated nucleation also occurs in pink gold alloys with Ir-additions, but two additional phenomena at high solidification speed [4]: (i) a spinodal-type decomposition of the liquid, leading to the formation of twinned Cu precipitates in addition to multi-twinned Au-rich grains; (ii) a change of the microstructure of the Au-rich grains, from 100 dendrites to 111 textured cells in the columnar zone. > [1] G. Kurtuldu, P. Jarry, and M. Rappaz, Influence of Cr on the > nucleation of primary Al and formation of twinned dendrites in > Al-Zn-Cr alloys: Can icosahedral solid clusters play a role? Acta > Mater. 61:7098–7108 (2013). > > [2] G. Kurtuldu, A. Sicco, and M. Rappaz, Icosahedral > quasicrystal-enhanced nucleation of the fcc phase in liquid gold > alloys. Acta Mater. 70:240–248 (2014). > > [3] G. Kurtuldu, Influence of Trace Elements on the Nucleation and > Solidification orphologies of fcc Alloys and Relationship with > Icosahedral Quasicrystal Formation. PhD thesis #6057, EPFL (2014). > > [4] J. Zollinger, B. Rouat, S. K. Pillai and M. Rappaz, Influence of > Ir additions and Icosahedral Short Ranger Order (ISRO) on nucleation > and growth kinetics in Au-20.5wt%Cu-4.5wt%Ag alloy. Acta Mater. > Submitted.