Effects of mechanical compression and autoclave treatment on the backbone clusters in the Al86Ni9La5 amorphous alloy

The microstructure and precipitates, thermal properties, microhardness and surface morphology of Al86Ni9La5 amorphous alloy fabricated with different circumferential speeds and treated by mechanical compression and autoclave have been studied. With increasing the circumferential speed Sc, onset temperature Tx2 of second crystallization and contraction degree δ of as-spun ribbons increase, but the pre-peak height and deformed zone size l near the microhardness indentation decrease, indicating that the backbone clusters are enhanced with increasing Sc. The backbone clusters can also be stabilized by 5 MPa compression and autoclave treatment. After 5 MPa compression and autoclave treatment, the Al-rich phases have formed in the ribbon with Sc = 14.7 m/s but are absent with Sc = 22.0 and 29.3 m/s. The number of the edge of the microhardness indentation, from which the shear bands emanate, is 4 in the as-spun and treated ribbons with Sc = 14.7 m/s, but is 2 or 3 in those with Sc = 29.3 m/s. Both facts together with the non-linear variation of expansion coefficient of as-spun ribbons suggest that the backbone clusters in the ribbons percolate as Sc increases up to 22.0 m/s.