Notch toughness of Fe-based bulk metallic glass and composites

The notch fracture toughness of Fe75Mo5P10C8.3B1.7 monolithic bulk metallic glass (BMG) and Fe77Mo5P9C7.5B1.5 and Fe79Mo5P8C6.7B1.3 BMG matrix composites with alpha-Fe as reinforcing phase, fabricated by suction mould casting, were evaluated. It was found that the monolithic BMG has a toughness of 27 MPa m(1/2), while the Fe77Mo5P9C7.5B1.5 BMG composite reinforced by single alpha-Fe dendrite phase exhibits a higher toughness of nearly 40 MPa m(1/2). However, for the Fe79Mo5P8C6.7B1.3 alloy with more dendrites, the toughness decreased up to 25 MPa m(1/2). Microstructure investigation reveals that the simultaneous formation of Fe-Mo-P hard brittle phase apart from alpha-Fe dendrites in the Fe79Mo5P8C6.7B1.3 alloy is the reason for the degradation of the fracture toughness. (C) 2011 Elsevier B.V. All rights reserved.