In-situ thermography and material characterization of scanning strategy effects in laser foil printing of Zr-based metallic glass

Purpose This paper aims to investigate the thermal behavior and amorphous stability of zirconium-based metallic glass (Zr65.7Cu15.6Ni11.7Al3.7Ti3.3) fabricated using the laser foil printing (LFP) technique. This study focuses on establishing the relationship between laser scanning strategies and melt pool cooling rates, emphasizing their influence on amorphous retention and crystallization behavior during multilayer deposition on Zr702 substrates. Design/methodology/approach In-situ thermography using a mid-wavelength infrared camera was applied to monitor the real-time temperature evolution of the melt pool and heat-affected zone. Finite element simulations were performed to analyze melt pool temperature gradients and transient heat transfer. Continuous and discrete welding strategies were compared to evaluate their effects on cooling rate and amorphous stability. Postprocess characterization, including X-ray diffraction, energy-dispersive spectroscopy and microhardness testing, was conducted to assess structural, compositional and mechanical changes induced by different thermal conditions. Findings Continuous welding produced larger and deeper melt pools due to sustained energy input, resulting in significant heat accumulation, and lower cooling rates that led to partial crystallization. In contrast, discrete welding achieved localized and intermittent energy input, generating higher and more stable cooling rates that effectively suppressed heat buildup. Consequently, fully amorphous structures were retained across multiple layers. Compositional analysis revealed a gradual decrease in zirconium content and enrichment of nickel and copper with increasing build height, while microhardness testing confirmed higher hardness values in samples fabricated using discrete welding. Originality/value This study provides new insights into the correlation between laser scanning strategy and thermal dynamics in the LFP processing of metallic glass. The findings demonstrate that discrete welding offers superior thermal control, enhanced amorphous retention and improved mechanical performance. The established process–structure–property relationship offers practical guidelines for advancing additive manufacturing of bulk metallic glasses with high thermal stability and reliability.