Abstract
The glass forming ability (GFA) of metallic glasses (MGs) is quantified by the critical cooling rate (RC). Despite its key role in MG research, experimental challenges have limited measured RC to a minute fraction of known glass formers. We present a combinatorial approach to directly measure RC for large compositional ranges. This is realized through the use of compositionally-graded alloy libraries, which were photo-thermally heated by scanning laser spike annealing of an absorbing layer, then melted and cooled at various rates. Coupled with X-ray diffraction mapping, GFA is determined from direct RC measurements. We exemplify this technique for the Au-Cu-Si system, where we identify Au56Cu27Si17 as the alloy with the highest GFA. In general, this method enables measurements of RC over large compositional areas, which is powerful for materials discovery and, when correlating with chemistry and other properties, for a deeper understanding of MG formation.
Highlights
The glass forming ability (GFA) of metallic glasses (MGs) is quantified by the critical cooling rate (RC)
The GFA for a large compositional space was directly determined using X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) mapping of alloy libraries heated with lasers at multiple scan speeds (Figs 3e and 4a)
The results are consistent with the region of highest GFA determined by nanocalorimetry, which is the range between Au58Cu25Si17 and Au52Cu29Si1921
Summary
The glass forming ability (GFA) of metallic glasses (MGs) is quantified by the critical cooling rate (RC). We present a combinatorial approach to directly measure RC for large compositional ranges. This is realized through the use of compositionally-graded alloy libraries, which were photo-thermally heated by scanning laser spike annealing of an absorbing layer, melted and cooled at various rates. We exemplify this technique for the Au-Cu-Si system, where we identify Au56Cu27Si17 as the alloy with the highest GFA This method enables measurements of RC over large compositional areas, which is powerful for materials discovery and, when correlating with chemistry and other properties, for a deeper understanding of MG formation. The majority of RC quantifications have been estimated using indirect methods This is due to challenges in experimentally measuring RC, for glass formers with RC exceeding 104 K s−1. Employing structural and chemical characterization, RC as a function of composition is determined and Au56Cu27Si17 was identified as the alloy with the highest GFA in the Au-Cu-Si system
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