A. Structure Informationamorphous Solid Formation and Interstitial Solution Behavior in Metallic Alloy Systems

Abstract

Models for the melt → amorphous solid transition and for the structure of amorphous solids in metallic systems will be reviewed. Experience suggests that the tendency toward formation of metallic glasses is greatest in systems composed mainly of noble or certain transition metals (A) admixed with smaller amounts of certain metalloidal or electropositive elements (B). Often the formation of the liquid states of these AB alloys is accompanied by heat evolution, excess entropy of mixing or some volume contraction. The effects of composition on alloy glass forming tendency will be discussed in view of these data and in terms of the structural models alluded to. We note also that the occurrence of ultra-fast impurity diffusion is in alloys where a B type element is the crystalline host and an A type element is the impurity. Experience shows quite conclusively that this rapid transport is effected primarily by interstitial type defects, which must, contrary to the empirical atom size ratio rules for solution behavior, be constituted by substantial proportions of the A component. The recent internal friction studies of Turner and associates suggest that in the lead-noble metal systems the defects have off-center interstitial configurations. We suggest that this interstitial solution behavior may stem from the same type of A-B interactions which are responsible for the strong glass forming tendency in alloys where A is the host. These interactions will be discussed in view of current correlations of alloying behavior

Interatomic potential to predict the glass-forming ability of Ni–Nb–Mo ternary alloys

“…It follows that the larger the driving force, the more easily the amorphous alloy can form or the more stable the obtained amorphous alloy, or the larger the size of the metallic glass obtained e.g., by copper-mold casting. To evaluate the related GFAs, some empirical or semi-empirical criteria, such as the deep eutectic criteria and size difference rule, have been proposed previously, yet they seem not to work very well, and there still exist some unsolved issues in this field [28,29]. In principle, both glass formation region and GFA could be considered as the intrinsic properties of a metal system and are governed by the interatomic interaction of the system.…”

Phase Diagrams and Glass Formation in Metallic Systems

“…[48] The deeper the eutectic or steeper the adjacent liquidus curves, the greater is the expected tendency for glass formation. In fact, deeper eutectics mean greater stability of the liquid and a relatively smaller degree of undercooling required for glass formation.…”

The best glass-forming compositions in Al–Co(or Ni)–Y ternary systems

“…Intense research efforts [2][3][4] have been focusing on the practical composition guidelines for the best glass-forming abilities (GFAs) as the traditional trial and error approach faces severe difficulties in these complex systems. With regard to GFA, Turnbull first pointed that glass formation should be the easiest at a eutectic composition [5]. Subsequently, the proposition was developed by Dubey and Ramachandrarao to show an asymmetry of GFA around the eutectic composition in most binary eutectic phase diagrams, GFA being larger on one side of the eutectic composition than on the other [6].…”