Mechanical-contact-induced transformation from the amorphous to the partially crystalline state in metallic glass

Abstract

Sliding friction and wear experiments and electron microscopy and diffraction studies were conducted to examine the metallurgical microstructure of a metallic glass surface strained in sliding contact. Friction and wear experiments were conducted with aluminium oxide spheres 3.2 and 6.4 mm in diameter sliding, in reciprocating motion, on a metallic foil with a composition of Fe 67Co 18B 14Si 1 at a sliding velocity of 1.5 mm s -1 (frictional heating is negligible) with a load of 2.5 N at room temperature and in a laboratory air atmosphere. The results of the investigation indicate that the amorphous alloy (metallic glass) can be crystallized during mechanical contact. Crystallites with a size range of 10–150 nm are produced on the wear surface of the amorphous alloy. A diffused honeycomb-shaped structure formed by dark gray bands is also produced during sliding. Considerable plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminium oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris and/or powdery and whiskery oxide debris. The wear rate of Fe 67Co 18B 14Si 1 was 5 × 10 -9 mm 3 N -1.