Minimizing Thermal and Microstructural Variations in Hybrid Additively Manufactured Aluminum Alloys: A Review

Hybrid additive manufacturing (HAM) of aluminum alloys integrates additive and conventional fabrication routes to achieve complex geometries, design flexibility, and material efficiency. Significant thermal and microstructural variations often occur between the built and substrate regions, despite the advantages of HAM. This can be attributed to differences in heat input, solidification rate, and thermal conductivity. These irregularities introduce residual stresses and uneven phase distributions, often creating weak interfacial zones that compromise strength, corrosion resistance, and dimensional precision. In this study, a critical examination of the origins and implications of thermal mismatch and microstructural heterogeneity in hybrid additively manufactured aluminum alloys is conducted. This study emphasizes the interaction between processing conditions, material composition, and build orientation, significantly influencing heat distribution and interfacial evolution in additively manufactured systems. Consequently, approaches such as substrate preheating, scan path optimization, compositional grading, and postdeposition heat treatments are discussed in relation to their capacity to mitigate these effects, hence promoting improved microstructural uniformity and enhanced interfacial cohesion. Furthermore, emerging modeling tools and advanced characterization techniques, like electron backscatter diffraction (EBSD) and high-resolution Scanning Electron Microscopy (SEM), are noted for their role in understanding microstructure–property relationships. The review concludes by identifying current challenges and proposing future pathways toward achieving thermal compatibility, enhanced reliability, and consistent performance in hybrid additively manufactured aluminum components.