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This study presents a fabrication method for preparing Ni using material extrusion-based 3D printing. First, the corresponding printing process window was optimized by exploring the relationship between the layer thickness and printing parameters (printing air pressure, printing speed, and printing height) of different solid content slurries, slurries rheology, and platform heating temperature. Then, the experiments on Ni slurries with different solid contents under different post-treatment methods were investigated to obtain the effect of solid content and temperature on the material properties. The results show that when the solid content of Ni slurry increases from 70 to 84 wt. %, the relative density of Ni increases, the shrinkage decreases, and the mechanical properties increase; when the sintering temperature increases from 1250 to 1400 °C, the relative density of Ni increases, the shrinkage increases, the mechanical properties decrease, and the particle size increases. The relative density range is 82%–96.6%, the shrinkage range is 53.5%–59.6%, the tensile strength range is 237.7–294 MPa, and the hardness range is 51.6–104.8 HV. Finally, the relationship between slurry, manufacturing process, structure, and properties was established through process optimization and experimental results, and 3D models of different structures were prepared to complete the preparation of Ni with high structural integrity, good interlayer bonding, and excellent properties. [ABSTRACT FROM AUTHOR]

In-situ core-shell structured particle Ti@(Al–Si–Ti) p reinforced A356 Al alloy matrix composites were prepared by powder-thixoforming at different partial remelting temperatures, and then were solid solution treated at 545 °C for 1 h. The results indicate that the reaction between Ti cores and Al matrix operates to form nano τ 2 particles during solutionization, while the original (Al, Si) 3 Ti phases transform into τ 2 phases, and simultaneously, the early-formed nano τ 2 particles grow into large-sized plates. These behaviors are enhanced with rising the remelting temperature. The content of eutectic Si and solubility of Si in α-Al phase in the solutionized composites further decrease with rising remelting temperature, due to the reaction and phase transformation, and de-dissolution of Si, respectively. The tensile properties of the solutionized composites first increase and then decrease as the temperature rises, and the composite thixoformed at 595 °C has the highest comprehensive mechanical properties, an ultimate tensile strength of 267.0 MPa, yield strength of 178.6 MPa and elongation of 21.0 %, increased by 3.1 %, 13.3 % and 15.4 % compared with those of the as-fabricated counterpart. • Reaction between Ti cores and Al maxtrix to form τ2 continues during solutionization. • (Al, Si) 3 Ti phase in the shells transforms into τ2-phase during solutionization. • Rsing partial remelting temperature enhances the above behaviors. • Rising partial remelting temperature decreases the solubility of Si in α-Al. • Tensile properties first increase and then decrease as the temperature exceeds 595 °C. [ABSTRACT FROM AUTHOR]

Ceramic particle reinforced medium entropy alloys (MEAs) coatings have attracted considerable attention because of their excellent hardness and wear resistance. In this study, (CoCrNi) 94 Al 3 Ti 3 MEA coating and (CoCrNi) 94 Al 3 Ti 3 -cBN MEA composite coating were prepared by high-speed laser cladding. The phase constituents, microstructure，hardness and wear mechanisms of the two coatings were investigated using XRD, Raman spectra, SEM, EDS, and TEM. Results show that (CoCrNi) 94 Al 3 Ti 3 comprises only simple FCC phase because of the high-entropy effect. However, the addition of cBN transforms the phase from FCC to FCC + BCC, but also generates micron-scale TiN and CoCr, as well as nanoscale TiN and CrB. In addition, part of the cBN is converted to hBN with lubricating effect under high energy laser. As for the properties, compared with (CoCrNi) 94 Al 3 Ti 3 coating, (CoCrNi) 94 Al 3 Ti 3 -cBN coating exhibits increased hardness by 2.2 times, increased wear resistance by 5.6 times, and decreased friction coefficient from 0.58 to 0.47. It is expected that this research will provide research ideas for the preparation coating of friction reduction and wear resistance performances on titanium alloy surfaces. [ABSTRACT FROM AUTHOR]

• The spall strength of tungsten alloy is weakly dependent on the peak stress. • With the increase of impact stress, cleavage fracture replaces intergranular fracture as the main fracture mode. • Twins appear near the crack of tungsten particles, which hinders the further propagation of cracks. • The {100}, {110} and {111} planes are the most potent macroscopic cleavage planes for the tungsten alloy. In this study, plate-impact experiments are conducted using tungsten heavy alloy (WHA) to obtain the free-surface velocity profiles under shock stress of 6–23 GPa. By analyzing the velocity wave profile, it is demonstrated that the spall strength is weakly dependent on the peak stress. The microstructure of the recovered WHA is well characterized and it's observed that intergranular fracture and cleavage are the primary fracture mechanisms. Deformation twins are sparsely distributed near the cleavage crack. The existence of twin boundary not only affects crack propagation but also regulates the crack path and reinitiates the cleavage propagation direction on the twin boundary. The macroscopic cleavage facet planes are detected to be {100}, {110} and {111} at all shock stress. [ABSTRACT FROM AUTHOR]

In this paper, nanoindentation processes of graphene nanocoating reinforced cemented carbide (G/WC-Co) is simulated using molecular dynamics method, from which the effect of the relative position of the indenter and Co on the mechanical properties of G/WC-Co is investigated. Visualization techniques are employed to reveal the microstructure evolutionary behavior of graphene during the nanoindentation process. The results show that the loading force of cemented carbide with graphene nanocoating during nanoindentation is 18.2050 μN, which is 135.47 % higher compared to 7.7312 μN, the loading force of bare cemented carbide. At a nanoindentation of 8.3 Å, sp3 bond increases sharply in graphene, which results in the transformation of graphene into diamond-like carbon (DLC). The simulation results indicate that at the beginning of nanoindentation, the substrate exhibits significant loading resistance due to the high shear modulus of graphene itself. With the further development of nanoindentation, graphene ruptures, and part of graphene evolves to form DLC film, which enhances mechanical property of cemented carbide substrate. [Display omitted] • A novel model has been developed, and the evolution of microstructure of the mechanical properties of G/WC-Co is investigated. • WC-Co reinforced with graphene nanocoating exhibits greater loading force (18.2050 μ N), which is 135.47% higher than that of bare WC-Co. • At a nanoindentation of 8.3 Å, sp3 bond increases sharply in grapheme, and the transformation of graphene into diamond-like film (DLC) occurs. • With the further development of nanoindentation, part of graphene has evolved into DLC film, significantly improving the mechanical properties of WC-Co substrate. [ABSTRACT FROM AUTHOR]