On the role of Sm in solidification of Al-Sm metallic glasses

Abstract

During the solidification of Al-Sm metallic glasses the evolution of the supercooled liquid atomic structure has been identified with an increasing population of icosahedral-like clusters with increasing Sm concentration. These clusters exhibit slower kinetics compared to the remaining clusters in the liquid leading to enhanced amorphous phase stability and glass forming ability (GFA). Maximum icosahedral-ordering and atomic packing density have been found for the Al 90 Sm 10 and Al 85 Sm 15 alloys, respectively, whereas minimum cohesive energy has been found for the Al 93 Sm 7 which is consistent with the range of compositions (from Al 92 Sm 8 to Al 84 Sm 16 ) found experimentally with high GFA.Keywords: metallic glass; short-range order; molecular dynamics; solidification.Metallic glasses (MGs) are known to have attractive mechanical properties such as high strength and high elastic limit, good corrosion and wear resistance and good biocompatibility [1,2,3]. However, the low glass forming ability (GFA) of some MGs has so far hindered synthesis of large MG specimens such as Al-base systems and therefore limited engineering applications of these materials. Many efforts have been devoted towards developing alloys with high GFA [1,4,5]. In particular, a number of studies focused on understanding of the MGs atomic structure and its relation to the MGs' mechanical properties

Nucleation kinetics in Al-Sm metallic glasses

“…The motivation for this analysis is that the concentration of ICO VPs has been previously argued to be correlated with the GFA of an alloy [40,41]. In this case, the ICO VPs are identified by applying the Voronoi tessellation technique [42] and then grouped based on their Voronoi indices [22]. We speculate that Sm can have an important effect on Al diffusion by increasing the fraction of ICO-like VPs [22].…”

“…In this case, the ICO VPs are identified by applying the Voronoi tessellation technique [42] and then grouped based on their Voronoi indices [22]. We speculate that Sm can have an important effect on Al diffusion by increasing the fraction of ICO-like VPs [22]. This would take place not only because Sm increases the fraction of Al-centered ICO-like VPs, but also because most of the Sm-centered clusters are ICO-like.…”

“…This observation is consistent with findings previously reported in literature. Specifically, Zhang et al[38] reported that the diffusion of Cu in a Cu-Zr MG is confined in the liquidlike regions that are poor in icosahedral short-range order, and Bokas et al[22] found that in Al-Sm MGs the diffusion coefficient of Al with ICO-like VP is one order of magnitude lower than other Al atoms at low Sm concentration range. In the same vein,Fig.…”

A self-contained algorithm for determination of solid-liquid equilibria in an alloy system

“…Thus, study of the effect of Sm concentration on Al nucleation in supercooled Al-Sm liquids can provide useful information for both glass formation and devitrification processes [26]. The driving force is a fundamental parameter that describes the net bulk free energy gain upon the formation of a crystalline nucleus.…”

Enthalpy of Mixing in Al–Tb Liquid

“…Even in binary glass-forming systems, clear evidence of the influence of ordering in the liquid state has been reported [3][4][5][11][12][13][14][15][16][17]. For example, the marginal glass-forming ability in the Al-RE (aluminum rare-earth) systems has been associated with ordering in the liquid phase [18][19][20][21][22][23][24][25][26][27][28][29]. In addition, due to their relative simplicity compared to conventional many-component glass-forming alloys, Al-RE and Al-RE-TM (TM denotes transition metal) alloys are excellent model systems for the investigation of phase stability [30][31][32][33], metallic glass formation [34][35][36][37], liquid properties and crystallization [38][39][40], and glassy alloy structure/properties [25,41,42].…”