Hardness, toughness, brittleness and cracking systems in an iron-based bulk metallic glass by indentation

The mechanical behaviour of an FeCoCrMoCBY bulk metallic glass is investigated by means of indentation testing and ultrasonic echography. The elastic moduli (Young's modulus of 225 GPa, Poisson's ratio of 0.337), hardness (13.5 GPa), indentation toughness (2.2MPam) and indentation brittleness (6 μm−1/2) are determined. Unlike most metallic glasses, this iron-based alloy exhibits cracking features above a critical load. The cracking systems are observed by means of stepwise polishing and consist in very shallow Palmquist (or radial) cracks, which is quite uncommon in other brittle materials such as glasses and ceramics.