Revisiting Al-Ni-Zr bulk metallic glasses using the ‘cluster-resonance’ model

Abstract

(x=1, 1.5, 2, 3) were designed in this work and the bulk metallic glass (BMG) formation of these compositions was investigated by copper mold suction casting. A centimeter-scale BMG sample was obtained for the Ni 4 Zr 9 Al 2 (Al 13.3 Ni 26.7 Zr 60 in atomic percent) composition. The thermal glass parameters for this BMG were determined to be ΔT x = 68 K, T rg = 0.579, and γ m = 0.689. Using the 'cluster-resonance' model for glass formation an optimal BMG composition was determined using the cluster formula [Ni 3 Zr 9 ](Al 2 Ni 1 ). . These complex alloys are based on the basic ternary systems of Al-TM-Zr (TM = Ni, Co, Cu) together with specific alloying substitutes [5,7,8]. A rationalization of the glass-forming abilities (GFAs) of Al-TM-Zr alloys is desirable to quantify complex BMG compositions. Disagreements exist with regard to experimental accounts of the GFA for fundamental ternary systems [9][10][11]. This study is devoted to a reexamination of the GFAs of Al-Ni-Zr alloys. We first use the 'cluster-plus-glue-atom' model [12,13] for BMG composition design. This model presents a semiphenomenological treatment of a BMG structure. An atomic cluster of specific topology, chemical composition and glue structure were used to establish the statistical composition of a BMG system. An ideal BMG assumes universal cluster formulae such as [cluster] 1 (glue atoms) x , with x=1 or 3 [13,14]. To determine the structural stability of the model structure we recently proposed a 'cluster-resonance' model by taking the coupling of long-range Friedel oscillations of valence electrons with the pair correlation function into consideration [15]. The composition design of Al-Ni-Zr BMG alloys is incorporated into the model that follows. The 'cluster-resonance' model and composition designAccording to Häussler et al. [16] the static atomic structure of an ideal amorphous state is in resonance with the longrange Friedel oscillations of valence electrons. The resonance results in spherical periodicity as shown by the peak (shell) oscillation with a certain period in the pair correlation function of an ideal amorphous state. The spherical periodicity gives an oscillation wavelength ( Fr ) in the form of

24 electron cluster formulas as the ‘molecular’ units of ideal metallic glasses

“…By replacing four Pd atoms with four Ni atoms, a cluster formula [PPd 4 Ni 4 ]P = Pd 40 Ni 40 P 20 (e/u = 23.3) falls exactly on the experimental composition Pd 40 Ni 40 P 20 , and this formula conforms to the random distribution of Pd and Ni as suggested by Egami et al[50].Bulk metallic glasses such as those in the Zr-Al-Co[51] and Zr-Al-Ni[52] systems have their principal clusters derived from the primary ternary devitrification phases Zr 6 Al 2 (Co,Ni) (InMg 2 -type). The good glass-forming compositions correspond to cluster formulas [Ni 3 Zr 9 ](Al 2 Ni) ≈ Zr 60 Al 13.3 Ni 26.7 (e/u = 23.9)[52] and [Co 3 Zr 9 ](Al 2 Co) ≈ Zr 60 Al 13.3 Co 26.7 (e/u = 23.9)…”

“…The good glass-forming compositions correspond to cluster formulas [Ni 3 Zr 9 ](Al 2 Ni) ≈ Zr 60 Al 13.3 Ni 26.7 (e/u = 23.9)[52] and [Co 3 Zr 9 ](Al 2 Co) ≈ Zr 60 Al 13.3 Co 26.7 (e/u = 23.9)…”

XPS Study on Barium Strontium Titanate (BST) Thin Films Etching in SF₆/Ar Plasma

“…There are also several reports investigating the properties of CF 4 /Ar plasmas both experimentally and theoretically. The etching mechanism of BST films has not been fully studied [14], perhaps because BST thin films are a relatively new material to the microelectronics technology. Thus, most work has focused on technological aspects, with etching mechanisms having received little attention.…”

Chemical composition dependence of atomic oxygen erosion resistance in Cu-rich bulk metallic glasses

“…So far, the field of AO erosion study is largely focused on crystalline materials. Recent decades, bulk metallic glasses (BMGs), new comers of metallic materials, have attracted lots of attention [10][11][12][13][14] due to excellent mechanical and functional properties [15][16][17][18][19][20][21], which are believed to be resulted by their unique structure [22,23]. Since high performance of BMGs make them potential candidates of space materials, their AO erosion resistance is of interest to be investigated.…”