Microstructural Change and Mechanical Properties with Isochronal Aging in Al-Ni-Gd Metallic Glasses

The changes of precipitation microstructures and mechanical properties during isochronal aging have been studied for melt-spun metallic glasses of Al-Ni-Gd ternary system. The fabricated Al₉₀Ni₃Gd₇, Al₈₇Ni₇Gd₆ and Al₈₅Ni₇Gd₈ ribbons were isochronally aged up to 400°C and then examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectrometry (EDX). It was found that two different intermetallic compounds of Al₂₃Ni₆Gd₄ and Al₁₉Ni₅Gd₃ as well as primary crystallized α-Al are formed by the isochronal aging in good agreement with the fact that three exothermic peaks are detected in the differential scanning calorimetry (DSC) curves. The highest nanoindentation hardness and Young’s modulus were obtained for the isochronally-aged Al₈₅Ni₇Gd₈, suggesting that not only the increase in Ni and Gd contents but also the isochronal aging is quite effective in strengthening the melt-spun Al-Ni-Gd alloys.