Nondestructive Testing of Welded Composite Metal Foams

Steel–steel composite metal foams (S–S CMFs) are advanced cellular materials with hollow stainless‐steel spheres within a stainless‐steel matrix, noted for low density, high specific strength, and exceptional energy absorption. This study investigates X‐ray computed tomography (CT) as a nondestructive testing method to evaluate welded CMF joints produced via induction welding, diffusion bonding, and brazing using Cu and BNi‐2 fillers. CT scans are used to evaluate number of through‐thickness voids and spatial void distribution at the bonded interface. Δ _Void metric is defined to quantify difference between postweld spatial void distribution and comparable preweld baseline to evaluate the influence of welding on mechanical performance and failure within samples. Substantial variation in Δ _Void of welded CMFs indicates near‐joint failure, while minimal variation in Δ _Void for welded CMFs informs away‐from‐joint failure. Δ _Void between −2.43% and + 0.41% indicates away‐from‐joint failure, while those beyond this range report near‐joint failure. Scanning electron microscopy (SEM) observations also corroborate that matrix porosities and void percentage influence joint mechanical performance. Results demonstrate the importance of combining CT and SEM techniques to understand microstructural characteristics affecting S–S CMF weld performance. CT enables detection and analysis of internal defects without compromising structure, ensuring safety, and regulatory compliance.