Structural periodicity in laser additive manufactured Zr-based bulk metallic glass

Abstract

Additive manufacturing of bulk metallic glasses (BMGs) allows for effective bypassing of critical casting thickness constraints for glassy alloys, opening up this exciting material class to new applications. An open question is how the laser processing of such materials affects the short-range structural order, a critical mediating parameter for glass deformation. Synchrotron X-ray microdiffraction was used to understand structural heterogeneity across the build-planes of a selective laser melted Zr-based BMG. While negligible macroscopic heterogeneity in the structure was observed over a 10 mm build height for the X-ray amorphous material, small periodic variations were observed on the order of 40–80 μm. This dimensional scale was rationalized as a consequence of melt-pool solidification from laser processing, which imparts a calculated local strain variation of ±0.1%. It is anticipated that this structural insight will help to rationalize microscale deformation effects from the periodic structural variation of selective laser melting produced BMGs.