Thermal Stability and Mechanical Properties of Cu-Based Bulk Glassy Alloys in Cu₅₀(Zr_1-xHf_x)₄₅Al₅ System

Abstract

The thermal stability, crystallization and mechanical properties of the Cu₅₀(Zr_1−xHf_x)₄₅Al₅ (x=0 to 1) bulk glassy alloys have been investigated. The glass transition temperature (T_g), crystallization temperature (T_x), liquidus temperature (T_l) and the supercooled liquid region ΔT_x (=T_x−T_g) increase with increasing Hf content. The reduced glass transition temperature (T_g⁄T_l) is in the range from 0.603 to 0.615. The Vicker’s hardness (Hv), Young’s modulus (E) and compressive fracture strength (σ_c,f) of the bulk glassy alloys increase linearly with increasing Hf content and reach the maximum values of 627, 121 GPa and 2262 MPa, respectively, for Cu₅₀Hf₄₅Al₅. A different crystallization behavior is observed for Cu₅₀Zr₄₅Al₅ and Cu₅₀Hf₄₅Al₅ glassy alloys. The final crystallization phases are Cu₁₀Zr₇ for the former alloy, and Cu₁₀Hf₇ and CuHf₂ for the latter alloy.