| Abstract Scope |
Fusion-based additive manufacturing of dissimilar metals faces major challenges due to interfacial cracking and chemical inhomogeneities. In this talk, I present operando synchrotron X-ray diffraction and imaging studies of laser powder bed fusion (LPBF) involving steel-copper, copper-nickel, and aluminum-copper alloy systems. Real-time diagnostics reveal distinct cracking modes—including solidification cracking, liquation cracking, and metal-induced embrittlement—arising from phase separation, compositional gradients, and large differences in solidification behavior. For example, in Cu-Ni systems, solidification cracking is driven by coexisting Ni-rich solid and Cu-rich liquid phases over a broad temperature range due to immiscibility. In Al-Cu systems, high-speed imaging uncovers discrete, stochastic material transport events—rather than continuous mixing—that govern interfacial homogenization. By linking thermodynamic modeling, real-time X-ray data, and post-mortem analysis, we pinpoint process windows and compositions that either trigger or suppress cracking. These findings provide a mechanistic foundation for improving the printability and structural integrity of complex multimaterial architectures. |