Preparation of Zr-based metallic glasses gradient composites with designable amorphous fraction by laser powder bed fusion

Abstract

Introducing ductile crystals in situ into the matrix is an efficient approach for enhancing the mechanical properties of bulk metallic glasses (BMGs). However, controlling the volume of the crystalline phase is challenging, and the introduction of crystals may be detrimental to its strength and ductility trade-off. In addition, BMGs prepared by conventional casting process suffers from the disadvantages of size limitation, inhomogeneous crystallization, and uncontrollable crystallization fraction. In this study, Zr48Cu47.5Al4Co0.5 amorphous powder with better forming ability was utilized as raw material and printed by selective laser melting (SLM) technique with high cooling rate. Through parameter adjustments and proactive design of amorphous fractions, gradient metallic glasses (GMGs) based on Zr has been successfully prepared. Micro-morphology, DSC tests, micro-area XRD, optical calculations and nanoindentation experiments all indicate the presence of gradient structures. The microstructure reveals that the crystalline phases in the heat affected zone (HAZ) are mainly B2 phase. In addition, the results of room temperature compression show that the yield strength (1.2 GPa) and plastic deformation (0.8 %) of the gradient structure are better than those of the samples prepared with a single parameter. The theme of amorphous fraction gradient structure design, realized by SLM technology, opens a new window for the large-scale development of high-performance BMGs.