Multi-material laser powder bed fusion (LPBF) additive manufacturing is a promising approach for integrating the functionality and mechanical performance of dissimilar materials into complex parts. This review offers a comprehensive overview of the recent advancements in multi-material LPBF, with a particular focus on compositionally heterogeneous/gradient parts and their fabrication methods and equipment, control of interfacial defects, innovative designs, and potential applications. It commences with the introduction of LPBF-processed compositionally heterogeneous/gradient structures with dissimilar material distributions, including Z-direction compositionally heterogeneous structures, compositionally gradient structures in the Z-direction and XY planes, and three-dimensional (3D) compositionally heterogeneous structures. Subsequently, various LPBF methods and equipment for fabricating compositionally heterogeneous/gradient structures have been presented. Furthermore, the interfacial defects and process control during LPBF for these types of compositionally heterogeneous/gradient structures are discussed. Additionally, innovative designs and potential applications of parts made from compositionally heterogeneous/gradient structures are illustrated. Finally, perspectives on the LPBF fabrication methods for compositionally heterogeneous/gradient structures are highlighted to provide guidance for future research.

Zinc (Zn) is considered a promising biodegradable metal for implant applications due to its appropriate degradability and favorable osteogenesis properties. In this work, laser powder bed fusion (LPBF) additive manufacturing was employed to fabricate pure Zn with a heterogeneous microstructure and exceptional strength-ductility synergy. An optimized processing window of LPBF was established for printing Zn samples with relative densities greater than 99% using a laser power range of 80 ~ 90 W and a scanning speed of 900 mm s⁻¹. The Zn sample printed with a power of 80 W at a speed of 900 mm s⁻¹ exhibited a hierarchical heterogeneous microstructure consisting of millimeter-scale molten pool boundaries, micrometer-scale bimodal grains, and nanometer-scale pre-existing dislocations, due to rapid cooling rates and significant thermal gradients formed in the molten pools. The printed sample exhibited the highest ductility of ~12.1% among all reported LPBF-printed pure Zn to date with appreciable ultimate tensile strength (~128.7 MPa). Such superior strength-ductility synergy can be attributed to the presence of multiple deformation mechanisms that are primarily governed by heterogeneous deformation-induced hardening resulting from the alternative arrangement of bimodal Zn grains with pre-existing dislocations. Additionally, continuous strain hardening was facilitated through the interactions between deformation twins, grains and dislocations as strain accumulated, further contributing to the superior strength-ductility synergy. These findings provide valuable insights into the deformation behavior and mechanisms underlying exceptional mechanical properties of LPBF-printed Zn and its alloys for implant applications.