Recent Advances in Crystalline Architecture and Defect Engineering of 3D-Printed Metals for Biomedical Breakthroughs: A Comprehensive Review

This comprehensive review examines how additive manufacturing parameters govern microstructural evolution and properties in metallic biomaterials. Powder bed fusion, direct energy deposition, and binder jetting produce distinct crystalline architectures through cooling rates of 10³–10⁸ K/s. Laser powder bed fusion yields refined CoCrMo microstructures (15.04 μm versus 102.47 μm cast), enhancing mechanical properties. Titanium alloys demonstrate tunable elastic moduli through compositional control, with Ti-45Nb achieving 60–62 GPa compared to Ti-6Al-4V's 110 GPa, approaching cortical bone's 10–30 GPa range. Controlled porosity (40–60%) optimizes osseointegration while maintaining structural integrity. Magnesium alloys exhibit grain refinement from 4.0 to 3.0 μm with increasing zinc content (4–7 wt%), directly affecting corrosion behavior. Heat treatment at 1000 °C maximizes stainless steel strength and corrosion resistance through sigma phase optimization. Process windows are established for each system, with energy densities from 56 J/mm³ (NiTi) to 110 J/mm³ (Ti-25Nb). Advanced characterization including millisecond-resolution synchrotron XRD and 4D imaging reveals phase transformations and defect dynamics. Multiscale modeling frameworks predict properties from atomic to component scales, providing quantitative guidelines for engineering biomaterials with precisely tailored properties for next-generation implants.