Influence of sub-glass transition heat-treatment on physical and structural properties of Cu46Zr44Al8Hf2 metallic glass

Abstract

The metastability of metallic glasses (MGs) can be altered via post-heat treatment around its glass transition temperature. Here, the influence of the short-term heat treatment slightly below the glass transition on the thermal, thermomechanical, and structural properties are investigated. The water-cooled copper mold casting is used to produce the Cu46Zr44Al8Hf2 MGs under argon gas. Heat treatment was performed by continuous heating at 20 °C/min to 400 °C, followed by immediate cooling. Samples were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) via continuously heating through its and (crystallization temperature) and by X-ray diffraction (XRD) in Bragg-Brentano (− 2) geometry. Main findings observed are (1) an increase in the thermal stability, − , registered by DMA and DSC, (2) a remarkable drop of the relaxation enthalpy in the DSC trace calculated from the change in specific heat before , (3) appearance of a third broad peak after heat-treatment in XRD, and (4) steady profile of ′ below correlated to the-relaxation in DMA. The unexpected increase in ∆ is linked to the release of the residual stresses accumulated during fast-quenching of the molten ingot down to room temperature. This stress can be estimated as 240 MPa on the outer surface and 100 MPa in the center of the cast CuZr-MG plates, which can be eliminated by the introduced heat-treatment method. Overall, this study suggests a direct and practical way to enhance the thermal stability and high strength retention of CuZr-based metallic glasses at elevated temperatures.

Comprehensive thermal analysis of a high stability Cu–Zr–Al bulk metallic glass subjected to high-pressure torsion

“…The GFA concentration range in the ternary Cu-Zr-Ti system can be predicted by the vacancy formation energy, mixing enthalpy and configurational entropy [20]. The short-term heat treatment below the glass transition (T g ) of a CuZr-based BMG yields an increase in the thermal stability and a significant drop of the relaxation enthalpy [21]. The improved GFA of a CuZrAl ternary BMGs is attributed to the suppression of the precipitation of Cu-Zr phase and the efficient dense packing of atoms.…”