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In response to the growing demand for advanced materials with inherent infection resistance, this research investigates the properties of 316L stainless steel with copper, produced through laser-directed energy deposition additive manufacturing. The study focuses on three compositions: pure 316L, 316L with 3 wt.% Cu, and 316L with 5 wt.% Cu. Compressive strength measurements and Vickers hardness tests were conducted to assess mechanical properties, while microstructural characterization and X-ray diffraction analysis provided insights into the material’s physical properties. This research extends beyond physical and mechanical properties by exploring the on-contact antibacterial efficacy against Staphylococcus aureus and Pseudomonas aeruginosa up to 72 h. The addition of Cu reduced the ability of bacterial colonization of both strains on the metal surface. The findings of this investigation have the potential to benefit the biomedical devices, contributing to both structural and biofunctional properties of materials. 

Balancing strength and ductility is crucial for structural materials, yet often presents a paradoxical challenge. This research focuses on crafting a unique bimetallic structure, combining non-magnetic, stainless steel 316L (SS316L) with limited strength but enhanced ductility and magnetic, martensitic 17-4 PH with higher strength but lower ductility. Utilizing a powder-based laser-directed energy deposition (L-DED) system, two vertical bimetallic configurations (SS316L/17-4 PH) and a radial bimetallic structure (SS316L core encased in 17-4 PH) were fabricated. Monolithic SS316L, 17-4 PH, and a 50% SS316L/50% 17-4 PH mixture were printed. The printed samples' phase, microstructure, room temperature mechanical properties, and fracture morphology were examined in as-printed conditions. Bimetallic samples exhibited both phases, with a smooth grain transition at the interface. Radial bimetallic samples demonstrated higher mechanical strength than other compositions, except 17-4 PH. These findings showcase the potential of the L-DED approach for creating functional components with tailored mechanical properties. 

Stainless steel 316L (SS316L) is widely used in fracture management devices. However, SS316L does not offer any bacterial infection resistance and can cause metal-ion sensitivity due to Ni-ions' presence. 17-4PH can emerge as a promising substitute due to the intrinsic antibacterial properties of copper, a 75% reduction in nickel content, and superior mechanical properties. SS316L and 17-4 PH were manufactured using laser-directed energy deposition (LDED). 17-4PH specimens surpassed the compressive strength of SS316L by over 150%. A static magnetic field was generated in 17-4 PH specimens to understand in vitro bone cell-material interactions. In vitro human fetal osteoblast cell culture and bacterial inhibition study using Staphylococcus aureus and Pseudomonas aeruginosa were carried out on these specimens with SS316L as control and as-processed and magnetized 17-4 PH as treatments. Results demonstrated that magnetized 17-4 PH exhibited 25% enhancement in hFOB proliferation and 70% reduction in bacterial colonization compared to SS316L. 

The demand for advanced materials has driven innovation in titanium alloy design, particularly in the aerospace, automotive, and biomedical sectors. Additive manufacturing (AM) enables the construction of multi-material structures, offering potential improvements in mechanical properties such as wear resistance and high-temperature capabilities, thus extending the service life of components such as Ti6Al4V. Directed energy deposition (DED)-based metal AM was used to manufacture radial multi-material structures with a Ti6Al4V (Ti64) core and a Ti6Al4V-5 wt.% B4C composite outer layer. X-ray diffraction analysis and microstructural observation suggest that distinct B4C particles are strongly attached to the Ti6Al4V matrix. The addition of B4C increased the average hardness from 313 HV for Ti6Al4V to 538 HV for the composites. The addition of 5 wt.% B4C in Ti6Al4V increased the average compressive yield strength (YS) to 1440 MPa from 972 MPa for the control Ti6Al4V, i.e., >48% increase without any significant change in the elastic modulus. The radial multi-material structures did not exhibit any changes in the compressive modulus compared to Ti6Al4V but displayed an increase in the average compressive YS to 1422 MPa, i.e., >45% higher compared to Ti6Al4V. Microstructural characterization revealed a smooth transition from the pure Ti6Al4V at the core to the Ti64-B4C composite outer layer. No interfacial failure was observed during compressive deformation, indicating a strong metallurgical bonding during multi-material radial composite processing. Our results demonstrated that a significant improvement in mechanical properties can be achieved in one AM build operation through designing innovative multi-material structures using DED-based AM. 

Directed energy deposition (DED)-based additive manufacturing (AM) was employed to fabricate three distinct bimetallic compositions to understand the role interface for the deformation behavior of bimetallic structures under compressive loading. Commercially pure titanium (CP Ti) with a hexagonal closed packed (HCP) structure, nickel (Ni) with a face-centered cubic (FCC), and tantalum (Ta) with a body-centered cubic (BCC) structure were selected to understand the deformation behavior within the pure metals and damage accumulation at the bimetallic interface. By incorporating the combination of these materials, such as Ni-Ti, Ni-Ta, and Ta-Ti, we aimed to manufacture layered-base polycrystalline composite structures with FCC-HCP, FCC-BCC, and BCC-HCP crystal unit cells, respectively. In Ni-Ti and Ni-Ta bimetallic structures, it was determined that deformation is controlled by the Ni region, where the highest deflection occurs when Ni bulges out and makes lateral stress at the interface, resulting in crack initiation, propagation, and failure of the structure. Structural edges were found to experience the highest deformation, prompting grain inclination towards the <111> crystal orientation, resulting in a favorable orientation for dislocation slip and a higher Taylor factor. However, strong interfacial bonding and similar Young's modulus between Ta and Ti altered the deformation mechanisms to twinning formation in the Ti region and observed buckling of the entire structure without significant failure at the interface. 

Powder contamination during laser powder bed fusion is a critical concern for the quality assurance of parts. Herein, we studied the effect of Inconel 718 contamination on the properties of printed Ti6Al4V, two commonly printed alloys. Contaminated parts exhibited visual and microstructural defects, and a mere 0.5wt% IN718 contamination resulted in a 43% reduction in plastic strain without noticing surface-level cracking. Further contamination of 2.5 wt% IN718 promotes surface cracking that renders the material unable to deform plastically, highlighting the importance of proper powder handling and the detrimental effects that even small amounts of contaminants can have on AM-produced components. 

In this study, we measured the tensile, compression, and fatigue behavior of additively manufactured Ti3Al2V as a function of build orientation. Ti3Al2V alloy was prepared by mixing commercially pure titanium and Ti6Al4V in 1:1 wt. ratio. Laser powder bed fusion-based additive manufacturing technique was used to fabricate the samples. Tensile tests resulted in an ultimate strength of 989 ± 8 MPa for Ti3Al2V. Ti6Al4V 90° orientation samples showed a compressive yield strength of 1178 ± 33 MPa and that for Ti3Al2V 90° orientation samples were 968 ± 24 MPa. By varying the build orientation to account for anisotropy, Ti32 45° and Ti32 0° samples displayed almost similar compressive yield strength values of 1071 ± 16 and 1051 ± 18 MPa, respectively, which were higher than that of Ti32 90° sample. Fatigue loading revealed an endurance limit (10 million cycles) of 250 MPa for Ti6Al4V and of 219 MPa for Ti3Al2V built at 90° orientation. The effect of the build orientation was significant under fatigue loading; Ti3Al2V built at 45° and 0° orientations displayed endurance limits of 387.5 MPa and 512 MPa, respectively; more than two-fold increment in endurance limit was observed. In conclusion, the superior attributes of Ti3Al2V alloy over Ti6Al4V alloy, as demonstrated in this study, justify its potential in load-bearing applications, particularly for use in orthopedic devices. 

High energy input creates enormous challenges for direct fusion bonding between dissimilar metals in wire‐arc directed energy deposition (DED). Vast differences in material properties, such as those between aluminum and stainless steel, cause significant compatibility issues. Their combination for higher performance is a compelling goal, but attempts are usually limited to nonadditive mechanical fastening. Wire‐based additive for direct fusion has never been attempted, and only powder‐based additive metal fusion manufacturing (AM) has shown any promise. Concentric radial deposition patterns are used in a wire‐arc DED system to produce a layer‐by‐layer in situ bimetallic coupling between AA5356 and SS308L to address this. The additively generated mechanical bond is held together by residual pressure, created by different thermal expansion coefficients between the concentric material bands during cooling. This produces a purely additive yet viable mechanical joint with minimal metallurgical bonding. Destructive testing defines the integrity of the additively coupled unit, with the radial overlap sustaining 732.96 Nm in torsion, 34.17 kN in tension, and a maximum of 475 MPa in compression. Fracture modes confirm the importance of concentric residual loads in creating the mechanically viable joint. Interfacial characterization shows a 300× reduction in crack width for concentrically constrained interfaces with narrowed diffusion zones.