Three-dimensional surface metrology analysis of cryogenically machined additively manufactured aluminium alloys

Abstract

Surface roughness and topography play a critical role in determining the performance and reliability of additively manufactured (AM) aluminium alloys, particularly after post-processing by machining. This study presents a comprehensive three-dimensional surface metrology analysis of machined additively manufactured Al-Si-10Mg aluminum alloy under varying cooling conditions, including dry, minimum quantity lubrication (MQL), air, and cryogenic CO2 environments. Surface characterization was performed using a Sensofar microscope operating in interferometry mode to acquire high-resolution 3D surface data. A full set of amplitude, spatial, and hybrid roughness parameters was evaluated, along with material ratio and volume parameters for functional assessment. The results show that at cutting speeds of 230–270 m/min, the average roughness (Sa) remained above 0.30 μm, while the root mean square roughness (Sq) ranged from 0.45 to 0.50 μm, indicating a smooth and periodic surface trend. Cryogenic cooling produced the most refined surfaces, with Sz values of 3.3–3.5 μm at 150–230 m/min and a moderate increase to 3.9–4.0 μm at 310 m/min. The results also show that the surface formation mechanisms of AM AlSi10Mg are significantly influenced by cooling conditions, leading to variations in texture orientation, roughness distribution, and material properties. In addition, the enhanced cooling conditions yielded improved surface integrity of AM AlSi10Mg, as measured by interferometry, reflected in lower roughness values and optimized core and valley volume parameters, which are beneficial for wear and fatigue related applications.