The <i>e/a</i> Criterion for the Largest Glass-forming Abilities of the Zr-Al-Ni(Co) Alloys

Abstract

Composition optimization for the largest glass-forming ability has been performed in the Zr-Al-Ni(Co) systems in this investigation. Two guiding criteria, termed respectively the e/a-constant criterion and the e/a-variant criterion, are applied. They are incarnated into the e/a = 1.5 composition line and the Zr 9 Ni(Co) 4 -Al composition line. Bulk metallic glasses are obtained by suction casting alloy melts of compositions within an e/a span of 1:3$1:5, with their thermal stabilities and glass forming abilities being increased with increasing e/a. The intersecting point of the two lines gives the composition Zr 53 Al 23:5 Ni(Co) 23:5 with the largest glass-forming ability.

Role of minor additions on metallic glasses and composites

“…Partial substitution of Mg by 1 at.% Y in the Mg 69 Zn 27 Ca 4 alloy is enough to partly crystallize a rod sample of 1 mm diameter and increase the strength from 550 to 1012 MPa. 62 This behavior was attributed to the formation of the crystalline phases Mg 12 …”

“…To predict the GFA, many parameters have been used over the years such as the supercooled liquid region DT x 5 T x À T g , the reduced glass transition temperature T rg 5 T g /T l and the c parameter [T x / (T g 1 T l )], where T x is the crystallization temperature, T g is the glass transition temperature and T l is the liquidus temperature. [11][12][13] Additionally, for Ti-based BMGs, the electronic structure (electrons per atom: e/a) is an important parameter to predict the GFA. 14 Metallic glasses exhibit interesting properties, such as high yield strength and low elastic modulus.…”

Development and Characterization of Low-Density Ca-Based Bulk Metallic Glasses: An Overview

“…The Ca-Mg-Al glasses do not contain heavy transition metals, and, therefore, they have the lowest densities among all Ca-based metallic glasses, as well as all other glasses. Their density varies in the range from 1.62 g/cm 3 …”

Development of Mg Based Amorphous Alloys with Higher Amounts of Rare Earth Elements

“…[9][10][11] Some successful examples have been achieved by applying the e=a-related criteria to predict the optimal multi-component compositions in Zrbased and Cu-based amorphous alloys. [18][19][20] The e=a-variant criterion is embodied in a ternary system by special e=a-variant line, which is defined by linking the third element to a special composition point in a binary subsystem, usually the deep eutectic point or a special atomic cluster composition. For the Mg-Cu-Gd ternary system, the f-shell electrons for Gd will lead to the uncertainty of the e=a ratio.…”