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 α-Fe as reinforcing phase, fabricated by suction mould casting, were evaluated. It was found that the monolithic BMG has a toughness of 27 MPa m1/2, while the Fe77Mo5P9C7.5B1.5 BMG composite reinforced by single α-Fe dendrite phase exhibits a higher toughness of nearly 40 MPa m1/2. However, for the Fe79Mo5P8C6.7B1.3 alloy with more dendrites, the toughness decreased up to 25 MPa m1/2. Microstructure investigation reveals that the simultaneous formation of Fe–Mo–P hard brittle phase apart from α-Fe dendrites in the Fe79Mo5P8C6.7B1.3 alloy is the reason for the degradation of the fracture toughness.

► We examine the notch fracture toughness of the three Fe-based alloys including one monolithic BMG, and two BMG matrix composites.
► The toughness could be significantly enhanced by formed single α-Fe dendrite.
► The intrinsic properties of precipitation phase play more important role in the fracture toughness rather than the formation of dendrite phase.