Unraveling the interrelation between process parameters and defects to enhance the strength of laser additively manufactured CuZrAlTi bulk metallic glass

Abstract

Laser powder bed fusion (LPBF) enables the production of large and intricately shaped bulk metallic glasses (BMGs); however, the current strength of LPBF-fabricated BMGs is significantly lower than their cast counterparts due to defects generated during the LPBF process in the as-built BMGs. In this study, considering the viscosity characteristics of BMG melts and their impact on melt pool characteristics, we investigated the relationship between LPBF parameters, structural characteristics, and defects in a selected Cu45Zr45Al6Ti4 BMG. Our findings revealed a transition of the melt pool from conduction mode to keyhole mode and subsequently to extended mode with increasing laser power. Furthermore, we explored how melt pool characteristics influence defects such as pores, heat affected zone (HAZ), and crystalline phase in the as-built Cu45Zr45Al6Ti4 BMG. Under optimized LPBF parameters, we successfully fabricated nearly fully amorphous Cu45Zr45Al6Ti4 BMG samples with high density (>99%) and absence of cracks. The printed samples exhibited a compressive strength of 1839 MPa comparable to their cast counterparts while achieving an impressive tensile strength value of 920 MPa, currently the highest reported for CuZr-based BMGs. This study enhances our understanding of the intrinsic relationship between LPBF parameters, melt pool characteristics, defects, and mechanical properties of LPBF-fabricated BMGs while providing a new parameter optimization strategy for reducing defects and achieving high strength in BMGs.

Keywords

• Bulk metallic glass
• Laser powder bed fusion
• Melt pool characteristics
• Microstructure
• Mechanical performance