Enhancing the mechanical properties of conventional ceramic particles-reinforced aluminum (Al 1060) metal matrix composites (AMCs) with lower detrimental phases is difficult. In this research work, AMCs are reinforced with graphene nanosheet (GNS) and hybrid reinforcement (GNS combined with 20% SiC, synthesized by shift-speed ball milling (SSBM), and further fabricated by two-pass friction stir processing (FSP). The effect of GNS content and the addition of SiC on the microstructure and mechanical properties of AMCs are studied. The microstructure, elemental, and phase composition of the developed composite are examined using SEM, EDS, and XRD techniques, respectively. Mechanical properties such as hardness, wear, and tensile strength are analyzed. The experimental results show that the GNS and the SiC are fairly distributed in the Al matrix via SSBM, which is beneficial for the mechanical properties of the composites. The maximum tensile strength of the composites is approximately 171.3 MPa in AMCs reinforced by hybrid reinforcements. The tensile strength of the GNS/Al composites increases when the GNS content increases from 0 to 1%, but then reduces with the further increase in GNS content. The hardness increases by 2.3%, 24.9%, 28.9%, and 41.8% when the Al 1060 is reinforced with 0.5, 1, 2% GNS, and a hybrid of SiC and GNS, respectively. The SiC provides further enhancement of the hardness of AMCs reinforced by GNS. The coefficient of friction decreases by about 7%, 13%, and 17% with the reinforcement of 0.5, 1, and 2% GNS, respectively. Hybrid reinforcement has the lowest friction coefficient (0.41). The decreasing friction coefficient contributes to the self-lubrication of GNSs, the reduction in the contact area with the substrate, and the load-bearing ability of ceramic particles. According to this study, the strengthening mechanisms of the composites may be due to thermal mismatch, grain refinement, and Orowan looping. In summary, such hybrid reinforcements effectively improve the mechanical and tribological properties of the composites.

The continuous drive friction welding of 6061-T6 Al and copper was investigated herein. The results show that with an increase in rotation speed, the width of the welded zone was gradually increased with the generation of higher temperatures, and the grain size in the dynamic recrystallization zone on the Al side first decreased and then increased due to the combined effect of heat and force. The microhardness on the bonding surface was significantly greater than that of the base materials due to the presence of intermetallic compounds, and there was a softening zone on both sides of the bonding surface, which was progressively more significant with an increase in the rotation speed. The ultimate tensile strength (UTS) of the welded joints first increased and then decreased with an increase in rotation speed. When the rotation speed was 1000 rpm, the UTS was at its peak value of 212 MPa, which reached 73.1% of the strength of the 6061-T6 Al base material.

The scattering of reinforcement plays a crucial role in the microstructure and properties of metal matrix composites. In this study, an aluminum matrix composite (AMC) was reinforced by 10 wt% TiO₂ (Al-10TiO₂), with an average particle size of a submicron, combined with a different content of graphitic carbon nitride (g-C₃N₄), which was fabricated by shift-speed ball milling (SSBM) combined with multi-pass friction stir processing (FSP). In addition to the high hardness of TiO₂, g-C₃N₄ has functional groups to promote in situ reactions. SSBM improves the distribution of reinforcement, refines grain size, and reduces the structural destruction of g-C₃N₄. The in situ reaction was achieved after multi-pass FSP at a high rotational speed and low travel speeds, which can promote uniform dispersion and grain refinement. Moreover, the g-C₃N₄ shows the efficient enhancement of strength while maintaining the elongation of AMC. Because the exfoliation of g-C₃N₄ under the effect of processing reduces the agglomeration of TiO₂, boosts the flattening of Al, and enhances interface integration with the base metal. In situ phases can reduce the generation of coarse phases and improve interfacial bonding ability to enhance mechanical properties. The maximum tensile strength has been found at about 172.5 MPa in the Al-10TiO₂ containing 1 wt% g-C₃N₄, which was enhanced by 34% compared to that of the Al-10TiO₂. The tensile strength increases when the g-C₃N₄ content increases from 0 to 1 wt%, but then reduces with a further increase of content. The hardness was increased by 50.2%, 60.2%, and 35% with a g-C₃N₄ content of 0.5, 1, and 2 wt% compared to AMCs without reinforcement, respectively. According to the test, the enhancement mechanism is mainly attributed to Orowan, grain refinement strengthening, and load transfer of scattered reinforcement. In summary, the utilization of hybrid reinforcements successfully enhances the microstructure and mechanical properties.

In recent years, lattice structures produced via additive manufacturing have been increasingly investigated for their unique mechanical properties and the flexible and diverse approaches available to design them. The design of a strut with variable cross-sections in a lattice structure is required to improve the mechanical properties. In this study, a lattice structure design method based on a strut cross-section composed of a mixture of three ellipses named a tri-directional elliptical cylindrical section (TEC) is proposed. The lattice structures were fabricated via the selective laser melting of 316L alloy. The finite element analysis results show that the TEC strut possessed the high mechanical properties of lattice structures. Compression experiments confirmed that the novel lattice structure with the TEC strut exhibited increases in the elastic modulus, compressive yield strength, and energy absorption capacity of 24.99%, 21.66%, and 20.50%, respectively, compared with the conventional lattice structure at an equal level of porosity.

Metamaterial lattice structures based on a Triply Periodic Minimal Surface (TPMS) structure have attracted much attention due to their excellent mechanical properties and energy absorption capabilities. In this study, a novel TPMS lattice metamaterial structure (IWP-X) is designed to enhance the axial mechanical properties by fusing an X-shaped plate with an IWP surface structure. A selective laser melting (SLM) machine was utilized to print the designed lattice structures with Ti6Al4V powder. The thickness of the plate and the density of the IWP are varied to explore the responsivity of the mechanical and energy absorption properties with the volume ratio of IWP-X. The finite element simulation analysis is used to effectively predict the stress distribution and fracture site of each structure in the compression test. The results show that the IWP-X structure obtains the ultimate compressive strength of 122.06% improvement, and the energy absorption of 282.03% improvement. The specific energy absorption (SEA) reaches its maximum value in the plate-to-IWP volume ratio of 0.7 to 0.8.