On the crystalline equilibrium phases of the Zr57Cu15.4Ni12.6Al10Nb5 bulk metallic glass forming alloy

Spherulitic crystallization behavior of a metallic glass at high heating rates

“…As a result, phase separation into several amorphous phases with different compositions is commonly observed to precede nanocrystallization in the Zr-Cu-Ni-Al-Nb BMG systems [6,29,30]. Furthermore, it has been demonstrated that in the Zr-Cu-Ni-Al-Nb alloy system, Cu (r ¼ 0.157 nm), Ni (r ¼ 0.162 nm), and to some degree Al (r ¼ 0.182 nm) can substitute for each other [9,31]. Therefore, the compositions of the nanocrystals are consistent with several known intermetallics: Zr 5 Al 3 Nb 2 with some Cu substitutions in Region A, Zr(Cu, Ni) with some Al substitutions in Region B, and Zr 2 (Cu, Ni) in Region D, although caution is advised as the measured Cu fractions may be high due to the contribution of the Cu grids used to support the FIB-milled TEM foils.…”

“…It has been reported that at low heating rates, polymorphic crystallization usually occurs in bulk metallic glasses (BMGs) since their compositions are close to deep eutectics [3,9,10]. Atomic redistribution occurs during crystallization in order to reach the equilibrium compositions of the crystalline phases, resulting in the formation of multiple nano-scale crystalline phases.…”

“…Atomic redistribution occurs during crystallization in order to reach the equilibrium compositions of the crystalline phases, resulting in the formation of multiple nano-scale crystalline phases. For instance, Zr 2 Cu, Zr 2 Ni and Zr 3 Al 2 intermetallics are among the most stable equilibrium crystallization products in several Zr-based BMG alloys [9,11,12]. On the other hand, micro-scale spherical crystals or spherulites have also been observed as the crystalline products in both binary [13] and multicomponent metallic glasses [14e16].…”

Properties of as-cast and structurally relaxed Zr-based bulk metallic glasses

“…1. Nb, one of the higher melting temperature (T m ) elements (T m = 2742 K), is often added to Zr-or Cu-based BMGs to investigate its influence on the BMGs' glass forming ability, corrosion resistance, and mechanical properties [17][18][19][20][21][22]25]. However, the melting temperatures of the Zr-and Cu-based BMGs are typically below 1200 K. Such a large discrepancy in the melting temperature of the constituent phases makes the melting process difficult, and often results in an incomplete melting of the refractory element.…”

“…The raw elemental Nb component was in the same shape of a u = 2.8 mm diameter wire. The one-step procedure is an often used method of preparing master-alloy ingots [17][18][19][20][21][22], i.e., arc melting all of the constituent elements into a master-alloy at once. In the two-step procedure [23], which has been commonly used in industry for preparing conventional alloys, binary ingots of Zr-Nb are fabricated first, followed by re-arc-melting it into master-alloy ingot with the remaining elemental components of Ni, Cu, and Al.…”