Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect when compared to their solid counterpart. The literature shows that porous Ti64 implants fabricated using different additive manufacturing (AM) process routes, such as laser powder bed fusion (L-PBF) and electron beam melting (EBM) can be tailored to mimic the mechanical properties of natural bone. This review paper categorizes porous implant designs into non-gradient (uniform) and gradient (non-uniform) porous structures. Gradient porous design appears to be more promising for orthopedic applications due to its closeness towards natural bone morphology and improved mechanical properties. In addition, this paper outlines the details on bone structure and its properties, mechanical properties, fatigue behavior, multifunctional porous implant designs, current challenges, and literature gaps in the research studies on porous Ti64 bone implants.

Creating complex structures using multiple materials in additive manufacturing comes with a unique set of challenges, particularly when it comes to how the materials transition and bond together. This research looks at a new powder binning method for combining metal powders to create multi-material components in a single build, all produced on a standard Laser Powder Bed Fusion EOS M 290 machine. The study focuses on the size and quality of the resulting multi-material interfaces and how different scan strategies used affect the interface strength. The strength of the interface between different material pairings is evaluated for combinations of 316 stainless steel bonded to Inconel 718, Inconel 718 bonded to Inconel 625, and Inconel 625 bonded to 316 stainless steel. The Ultimate Tensile Strength (UTS) and interface region lengths were calculated to be 675 MPa and 1250 µm for 316L–IN718, 1004 MPa and 2500 µm for IN718–IN625, and 687 MPa and 2000 µm for IN625–316L, respectively. The findings show that the laser powder bed fusion material binning method is comparable to traditional methods, such as welding or directed energy deposition. This suggests that the new material binning method offers clear advantages when it comes to enabling complex geometry multi-material components while maintaining the strength and durability of the bonds between different metal materials found in traditional means. Further, optimization of scan strategies in the interface zones could play a significant role in improving the overall performance of these multi-material components, which is particularly important for industries such as aerospace, automotive, and energy production.

Growing attention in additive manufacturing (AM) of high-entropy alloys has intensified the demand for techniques in creating high-quality powder for AM. This study characterizes the effectiveness of a multifunctional vacuum arc melting (VAM) and ultrasonic-plasma atomization (UPA) system for creating TiZrNbHfTa powder. The focus is to evaluate the morphology, microstructural homogeneity, and phase composition of ultrasonically atomized powder to assess process capability for preparing powder feedstock for AM. Atomized powder was sieved into three size ranges, 15–63 µm, 63–125 µm, and 125–250 µm for characterization by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), and micro-computed tomography (micro-CT). SEM, EDS, and XRD results show that the powder is highly homogenous with an elemental distribution independent of powder size range and a microstructure comprising a BCC solid solution and minor monoclinic Ti oxide. Micro-CT scans indicate low porosity (0.24%, 0.08%, 0.24%) and high sphericity (0.93, 0.90, 0.93) for the 15–63 µm, 63–125 µm, and 125–250 µm distributions, respectively. Overall, the key innovation of this study is the successful application of ultrasonic atomization to produce high-quality TiZrNbHfTa refractory high-entropy alloy powder for additive manufacturing, a technique that has a limited scope of research. Specifically, this work demonstrates that ultrasonic atomization can produce highly homogeneous powder with high sphericity, low porosity, and a particle size distribution suitable for laser powder bed fusion and powder directed energy deposition, establishing ultrasonic atomization as a viable route for producing refractory high-entropy alloy powder for AM.

This study presents a detailed microanalysis and microstructural characterization of the multi-material 316L–IN718 system produced in a prior work by the powder binning method for Laser Powder Bed Fusion (L-PBF), in which these multi-material samples were fabricated in a single build and then mechanically tested. This effort extends the investigation by applying X-ray micro-computed tomography (Micro-CT), electron backscatter diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques to specimens produced under the baseline single-scan condition to examine the interface transition in volumetric porosity, crystallographic structure, and elemental composition. Micro-CT analysis revealed that the interface region exhibited the highest void volume ratio among the three analyzed regions, reaching 0.91%, compared to 0.32% for 316L and 0.37% for IN718. The interface also contained the largest defects, including the only voids with volumes exceeding 500,000 µm³, indicating that critical flaws, while not widespread, were concentrated at the dissimilar material boundary. EDS line scanning across four locations along the interface confirmed a diffuse compositional transition that closely and consistently supports the interface width independently reported via microhardness for the same material pairing in the original study. EBSD mapping showed a gradual grain structure transition with coarser equiaxed grains on the 316L side, and the entire scan indexed successfully with a single face-centered cubic structure file, with no secondary or intermetallic phases detected at the resolution of the measurement. Collectively, these results explain the failure behavior reported previously: the compositionally strengthened, defect-rich interface sheds plastic strain into the adjacent, softer 316L, which fails first due to its lower strength and coarser void population. Under monotonic tensile loading, improving binning-based multi-material performance therefore depends primarily on strengthening or targeting defect-reduction strategies at the weaker 316L constituent.