MICROSTRUCTURAL CHANGE AND MECHANICAL PROPERTIES WITH ISOCHRONAL AGING IN Al-Ni-Gd METALLIC GLASSES

摘要

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 Al_(90)Ni_3Gd_7, Al_(87)Ni_7Gd_6 and Al_(85)Ni_7Gd_8 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 Al_(23)Ni_6Gd_4 and Al_(19)Ni_5Gd_3 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 Al_(85)Ni_7Gd_8, 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.