Influence of in situ ceramic reinforcement towards tailoring titanium matrix composites using laser-based additive manufacturing

Influence of nano-BN inclusion and mechanism involved on aluminium-copper alloy

Taking advantage of the high specific surface area of the nanoparticles, boron nitride (BN) nanoparticles were incorporated into the semi-solidified aluminium-copper alloy Al-5Cu-Mn (ZL201) system during the casting process, and its properties and enhancement mechanism were studied. The results shown that the BN in the new composite material is more uniformly distributed in the second phase (Al2Cu), which can promote grain refinement and enhance the bonding with the aluminium-based interface, and the formation of stable phases such as AlB2, AlN, CuN, etc. makes the tensile strength and hardness of the material to be significantly improved (8.5%, 10.2%, respectively). The mechanism of the action of BN in Al2Cu was analyzed by establishing an atomic model and after calculation: BN can undergo strong adsorption on the surface of Al2Cu (0 0 1), and the adsorption energy is lower at the bridge sites on the two cut-off surfaces, which makes the binding of BN to the aluminum base more stable. The charge transfer between B, N and each atom of the matrix can promote the formation of strong covalent bonds Al-N, Cu-N and Al-B bonds, which can increase the dislocation density and hinder the grain boundary slip within the alloy.

Microstructure Evolution and Mechanical Properties of Needle-Like ZrB2 Reinforced Cu Composites Manufactured by Laser Direct Energy Deposition

Laser additive manufacturing is an advanced material preparation technology, which has been widely used to prepare various materials, such as polymers, metals, ceramics and composites. Zirconium diboride (ZrB2) reinforced copper composite material was fabricated using laser direct energy deposition technology. The microstructure and phase composition of the composite material were analyzed, and the influence of laser energy density on the microstructure and mechanical properties of composite materials was discussed. The results showed that the needle-like ZrB2 ceramic reinforcement was successfully synthesized via an in-situ synthesis reaction. The composites were mainly composed of needle-like ZrB2, Ni dendrites and a Cu matrix. The morphological changes of Ni dendrites could be observed at the interface inside the composite material: cellular crystals → large-sized columnar dendrites → small-sized dendrites (along the solidification direction). The continuous Ni dendritic network connected the ZrB2 reinforcements together, which significantly improved the mechanical properties of the composite material. At a laser energy density of 0.20 kJ/mm2, the average microhardness of the composite material reached 294 HV0.2 and the highest tensile strength was 535 MPa. With the laser energy density increased to 0.27 kJ/mm2, the hardness and tensile strength decreased and the elongation of the Cu composites increased due to an increase in the size of the ZrB2 and a decrease in the continuity of the Ni dendritic.

Biotribocorrosion of 3D-Printed silica-coated Ti6Al4V for load-bearing implants

Laser-based 3D Printing was utilized to deposit a silica (SiO₂) coating on the surface of Ti6Al4V (Ti64) alloy for implementation onto articulating surfaces of load-bearing implants. The surface laser melting (SLM) technique was implemented in 1, and 2 laser passes (1LP and 2LP) after SiO₂ deposition to understand the influence of remelting on the coating's hardness and tribological performance. It was observed that compositional and microstructural features increased the cross-sectional hardness. Wear rate was observed to decrease from 2.9×10^-4 in the Ti64 to 5.2 ×10^-6, 3.8×10^-6, and 2.1×10^-7 mm³/Nm for the as-processed or zero laser-pass (0LP), 1LP, and 2LP, respectively. Coated samples displayed a positive shift in open-circuit potential (OCP) during linear wear by displaying a 368, 85, and 613 mV increase compared to Ti64 for 0LP, 1LP, and 2LP, respectively. Our results showed promising tribological performance of SiO₂ coated Ti6Al4V for articulating surfaces of load-bearing implants.

Nature-inspired materials and structures using 3D Printing

Emulating the unique combination of structural, compositional, and functional gradation in natural materials is exceptionally challenging. Many natural structures have proved too complex or expensive to imitate using traditional processing techniques despite recent advances. Recent innovations within the field of additive manufacturing (AM) or 3D Printing (3DP) have shown the ability to create structures that have variations in material composition, structure, and performance, providing a new design-for-manufacturing platform for the imitation of natural materials. AM or 3DP techniques are capable of manufacturing structures that have significantly improved properties and functionality over what could be traditionally-produced, giving manufacturers an edge in their ability to realize components for highly-specialized applications in different industries. To this end, the present work reviews fundamental advances in the use of naturally-inspired design enabled through 3DP / AM, how these techniques can be further exploited to reach new application areas, and the challenges that lie ahead for widespread implementation. An example of how these techniques can be applied towards a total hip arthroplasty application is provided to spur further innovation in this area.