Process-dependent anisotropic thermal conductivity of laser powder bed fusion AlSi10Mg: impact of microstructure and aluminum-silicon interfaces

• Published in: Rapid prototyping journal 2023-06, Vol.29 (6), p.1109-1120
• Main Authors: Azizi, Arad, Hejripour, Fatemeh, Goodman, Jacob A., Kulkarni, Piyush A., Chen, Xiaobo, Zhou, Guangwen, Schiffres, Scott N.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Alloys; Aluminum alloys; Aluminum base alloys; Conductivity; Corrosion resistance; Crystal defects; Crystallography; Electron backscatter diffraction; Energy; Engineering; Frequency domain analysis; Grain orientation; Grain size; Heat conductivity; Heat exchangers; Heat pipes; Heat sinks; Heat transfer; Laser applications; Lasers; Materials Science; Mechanical properties; Microstructure; Nondestructive testing; Particle size; Pipes (defects); Powder beds; Rapid prototyping; Silicon; Solidification; Substrates; Thermal conductivity; Thermal energy; Thermal resistance; Thermodynamic properties
• ISSN: 1355-2546; 1758-7670; 1355-2546
• DOI: 10.1108/RPJ-09-2022-0290

Purpose AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity. Design/methodology/approach The thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity. Findings The highest through-plane thermal conductivity (136 ± 2 W/m-K) was achieved at 59 J/mm3 and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 ± 2 W/m-K at 50 J/mm3. The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains. Practical implications The thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications. Originality/value To the best of the authors’ knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstruc