Architectured AlN/Al composites produced by material extrusion and pressure infiltration: processing–structure–property relationships

This work presents a hybrid manufacturing route combining material extrusion of porous AlN preforms with pressure-assisted aluminum infiltration for the fabrication of architectured AlN/Al composites. Porous AlN preforms were produced by Material Extrusion (MEX) Fused Granulate Fabrication (FGF), followed by debinding and sintering to obtain an interconnected ceramic framework. The porous AlN line infill structures were subsequently infiltrated with molten aluminum alloy under pressure, resulting in a dense interpenetrating ceramic–metal composite. Physical parameters and the microstructural evolution throughout the processing route was investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray computed tomography (XCT). Microstructural observations confirmed homogeneous aluminum distribution and a well-defined AlN/Al interface throughout the composite. Tomographic analysis revealing a final composite containing 75.4 vol.% AlN and 24.6 vol.% Al. The overall porosity determined by X-ray tomography and microstructural analysis was approximately 0.68 vol.%. Thermomechanical characterization showed stable behavior up to 500°C, with coefficients of thermal expansion ranging from 11.6 to 12.9 × 10⁻⁶ K⁻¹ after thermal stabilization. Compression testing revealed moderate anisotropy associated with the printed architecture, with average compressive strengths of 511 MPa and 567 MPa in the XY and Z directions, respectively.