Laser powder bed fusion (LPBF) additive manufacturing has been advancing in the fabrication of metallic multi-material structures with intricate structures and refined material layouts. Herein, a comprehensive review of the recent achievements of multi-material structures via LPBF is provided in terms of interface characteristics and strengthening methods, critical technical issues and potential applications. It begins with the introduction of multi-material structures and the scope of the review. The interface characteristics (including representative multi-material types printed by LPBF, interfacial microstructure, defects, etc.) and strengthening methods of multi-material structures are then presented. Thereafter, the critical technical issues in LPBF for multi-material structures are discussed with regard to equipment development, data preparation, thermodynamic calculation and process simulation, and powder cross-contamination and recycling. Moreover, the potential applications (particularly in biomedical, electronic, aerospace) are illustrated and discussed. Finally, the outlook is outlined to provide guidance for future research.

Metal additive manufacturing (AM) has tremendous potential for manufacturing geometrically complex metallic products with freedom of design and desirable performance. Qualification and certification are critical to ensuring the successful adoption of metal AM by various sectors and accelerating the standardisation progress. This article provides a comprehensive review on the status of standardisation and challenges for the qualification and certification of metal AM, which is a timely summary to bridge the readiness gap between metal AM technologies developed at academia and industry. It begins with introducing fundamentals of metal AM qualification and certification. Thereafter, the status of standards, rules, and regulations developed by international organisations and communities is summarised and discussed. The challenges are then addressed, including the qualification and certification process, materials, process reliability and repeatability, post-processing, data, and standards and protocols. Finally, the conclusion and future outlook are drawn to provide guidance for future research and development.

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.