Programmable Lamellar Eutectic Zn‐2Al‐Mg Biodegradable Implants Manufactured by Laser Powder Bed Fusion for Synergistic Strength‐Ductility and Osteogenesis
Cijun Shuai, Desheng Li, Xie Hu, Yao Xiong, Shuping Peng, Chengde Gao
Abstract
Zn emerges considerable potential for bone repair as a biodegradable implant due to its biodegradability, good biocompatibility, and biofunctions. Nevertheless, the clinical applications of Zn encounter a profound bottleneck arising from insufficient mechanical properties and relatively slow degradation. In this work, novel Zn-2Al-Mg eutectic implants are developed by laser powder bed fusion (LPBF), aiming to overcome the mechanical dilemma meanwhile endowing remarkable osteogenesis. During LPBF, Mg-doping effectively lowers the eutectic point by altering Zn/Al ratio, promoting eutectic nucleation. Further, lamellar eutectic in Zn-2Al-Mg alloys is programmable by manipulating Mg-doping and non-equilibrium rapid solidification of LPBF. Consequently, Zn-2Al-0.3Mg eutectic exhibits a remarkably enhanced strength (155.1 MPa) and ductility (10.6%). This synergistic mechanical reinforcement is motivated by initial dislocation-mediated plastic deformation due to heterogeneous eutectic interface and incremental strain-hardening capacity owing to extra grain boundary slips. Also, Mg-doping accelerates the degradation of Zn-2Al-Mg implants, thereby promoting biocompatibility and antibacterial activity. Furthermore, in vivo bone repair surgery on rabbit radiuses demonstrates that as-printed Zn-2Al-Mg implants possess satisfying osteogenesis and osseointegration, evidenced by abundant formation and ingrowth of new bone tissues. Overall, this study not only develops a promising candidate for biodegradable alloys but also sheds light on designing and manufacturing state-of-the-art biomedical implants.