Effect of Minor Alloying Substitution on Glass-Forming Ability and Crystallization Behavior of a Ni₅₇Zr₂₂X₈Nb₈Al₅ (X = Ti, Cu) Alloy Synthesized by Mechanical Alloying

Abstract

Ni₅₇Zr₂₂X₈Nb₈Al₅ (X = Ti, Cu) metallic glass (MG) and nanocomposite powders were synthesized by mechanical alloying. Outstanding differences in glass-forming ability (GFA), thermal property, particle size and crystallization behavior were found for the two synthesized alloy powders with different alloying substitutions. The Ti-containing MG powder exhibits better GFA, higher thermal stability, lower enthalpy of crystallization and smaller particle size compared with the Cu-containing nanocomposite powder, respectively. Meanwhile, the crystallization of the Ti-containing MG powder is governed by typical volume diffusion-controlled three-dimensional growth. The better GFA for the Ti-containing alloy system could be explained by appropriate atomic-size mismatch and large negative heat of mixing among main constituent elements. The higher enthalpy of crystallization for the Cu-containing nanocomposite powder leads to the lower thermal stability and larger particle size of the powder than Ti-containing MG powder.