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Description
Porosity in Laser Powder Bed Fusion (L-PBF) aluminium alloys strongly influences heat diffusion mechanisms and, in turn, the mechanical behaviour of additively manufactured components. This motivates the development of non-destructive approaches capable of probing porosity through thermophysically meaningful quantities. This study presents a preliminary investigation on the use of thermal effusivity, estimated by pulsed laser thermography, as a proxy for porosity in L-PBF AlSi10Mg.
Bi-layer specimens were manufactured by intentionally combining a nearly dense surface layer with a porous substrate, obtained through systematic variations of hatch spacing during the L-PBF process. Localized pulsed laser spot thermography in reflection mode was employed to generate transient thermal fields, which were recorded by an infrared camera under controlled boundary conditions. The measured temperature decays were analysed using an effective bi-layer inverse thermal model, allowing the estimation of the in-depth thermal diffusivity of the dense surface layer and the thermal reflection coefficient at the layer–substrate interface. These parameters were subsequently used to derive the effective thermal effusivity of the porous substrate.
The reconstructed effusivity shows a clear, monotonic dependence on porosity, whereas the thermal diffusivity of the dense surface layer remains nearly constant across the investigated specimens. Since porosity is known to govern stiffness and strength in L-PBF AlSi10Mg, the observed effusivity trends suggest a potential link between thermographically estimated thermal parameters and porosity-driven variations in mechanical properties, without requiring direct mechanical testing. Although the present results are limited to a preliminary dataset, they demonstrate the feasibility of using thermal effusivity as an indirect indicator of porosity. The proposed approach highlights the potential of pulsed laser thermography combined with bi-layer modelling as a physics-based framework for non-destructive porosity assessment in L-PBF aluminium alloys, paving the way for future extensions towards comprehensive thermo-mechanical validation.
