Absorptivity scaling behaviour during laser powder bed fusion of copper alloys

Published

August 1, 2026

Author(s)

Sagar Patel, David Deisenroth, Alimehr Peyman, Mihaela Vlasea

Abstract

Copper (Cu) and its alloys are used in many industries owing to their high thermal and electrical conductivity, alongside their corrosion resistance and antimicrobial properties. The adoption of Cu-alloys in laser powder bed fusion (PBF-LB) is limited by the high reflectivity of these alloys, particularly at near-infrared wavelengths commonly used in commercial PBF-LB systems. In this work, the absorptivity scaling behaviour of a Cu-alloy (C14500, >99.40% Cu) is characterized using an open-architecture in situ reflectivity measurement setup within an additive manufacturing metrology testbed (AMMT). Reflectivity measurements are taken for 56 process parameter combinations of laser power, velocity, and beam diameter, which capture the range of conduction to keyhole melting modes during PBF-LB of Cu-alloys. Additionally, the absorptivity scaling behaviour for C14500 powder spread on a printed substrate is compared with that of a machined substrate and literature data from calorimetry absorptivity measurements for Ti-, Fe-, and Ni-alloys, to evaluate the effects of substrate roughness and material reflectivity with near-infrared lasers on absorption behaviour in PBF-LB. The results from this work represent a significant advancement in energy coupling physics by demonstrating that the steady-state PBF-LB interactions for copper alloys are governed not only by the intrinsic reflectivity of the material, but also by a surface topography-induced multiple reflections and powder entrainment mechanism. The extreme reflectivity in copper during near-infrared PBF-LB allows for an absorptivity saturation point of 0.91 on printed surfaces and 0.77 on machined surfaces. This distinct behaviour is attributed to the roughness of the printed substrate (which leads to an increased number of scattering events, alongside reduced effects of the Brewster's angle and the realistic powder layer spreading deployed, enhancing the amount of powder particles captured by the melt pool and thereby beam absorption. The measured absorptivity values are analysed using dimensionless parameters, such as normalized enthalpy and diffusion length, to develop an absorptivity scaling equation for PBF-LB of Cu-alloys. This absorptivity scaling equation quantifies laser energy absorption as a function of key PBF-LB parameters and material properties, thereby enhancing predictive capabilities for translation to other Cu-alloys and PBF-LB systems.

Citation

Journal of Materials Processing Technology

Pub Type

Journals

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Keywords

Additive manufacturing, Laser powder bed fusion, Absorptivity scaling, Copper alloys, Laser keyhole, In situ monitoring, Metal powder absorptivity

Citation

Patel, S. , Deisenroth, D. , Peyman, A. and Vlasea, M. (2026), Absorptivity scaling behaviour during laser powder bed fusion of copper alloys, Journal of Materials Processing Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=961484 (Accessed August 20, 2026)

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