Multi-walled carbon nanotube (MWCNT)/Cu composite containing 0.5 vol% MWCNTs were prepared by a high energy ball milling followed by conventional sintering and finally cold rolling. Microstructure studies showed that MWCNTs were uniformly dispersed and implanted inside the Cu matrix. The MWCNT/Cu composites showed an improvement in hardness and tensile strength up to 37% and 44% respectively compared to those of pure Cu. The enhancement is attributed to the uniform dispersion and strengthening due to the addition of MWCNTs. The yield strength of the composite has been quantified by several strengthening mechanisms including grain boundary strengthening, dislocation strengthening, Orowan strengthening and load transfer. The calculated results indicated that the load transfer strengthening has the largest contribution to the yield strength of the composite which implied the key role of the interfacial bond strength between MWCNTs and Cu matrix on the strengthening behaviors. The friction coefficient and specific wear rate of the composites were reduced with the addition of MWCNT content due to the self-lubrication effect of CNTs and high mechanical properties.

Permeability and capillary performance are the most important parameters relating to the thermal performance of heat pipes. These parameters are deeply linked to pore structure, which has been influenced by the starting powder utilized. In this paper, the effect of particle size and geometry of copper powder on the porosity and capillary performance of porous wicks were systematically studied. Sintered porous wicks were made from different-sized spherical (58 μm, 89 μm, 125 μm) and dendritic (59 μm, 86 μm, 130 μm) Cu powders. The results demonstrated that the porosity and capillary performance of both types of copper powder increase with particle size due to an increase in the connectivity between internal pores. In comparison to the spherical powder, the dendritic powder demonstrated superior capillary efficiency as well as greater porosity. Additionally, a model was proposed for the capillary performance and permeability of sintered porous copper. The predicted results were quite comparable to the experimental data, demonstrating the effect of the starting powder. These findings suggest that porosity and capillary performance of porous wicks are strongly related to powder geometry as well as particle size.

In this paper, we investigated the effect of the different sintering techniques including vacuum sintering, capsule-free hot isostatic pressing (HIP), and capsule HIP on the microstructure and mechanical properties of Ti6Al4V alloy. The obtained results indicated that full density Ti6Al4V alloy could be obtained by using capsule HIP technique. The alloy sintered by capsule HIP had the highest hardness (~405 HV) and compressive yield strength (~1056 MPa). It is interesting that the geometry has a significant influence on the relative density and mechanical properties of the alloy sintered by the capsule-free HIP. The relative density, hardness, and compressive yield strength rise from center to periphery of the specimen. This is attributed to the heating and pressing in the capsule-free, which are external, leading to the densification processes starting from the outside to the inner parts of the pressed specimen. Using theoretical prediction with Gibson and Ashby power law found that the yield strength of the alloy sintered by capsule-HIP technique is much lower than that of the calculated value due to the formation of the coarse lamellar microstructure of α-Ti grains.

In this study, the effect of powder preparation techniques on microstructure, mechanical properties, and wear behaviors of graphene-reinforced copper matrix (Gr/Cu) composites was investigated. The composite powders were prepared by two different techniques including high-energy ball (HEB) milling and nanoscale dispersion (ND). The obtained results showed that the ND technique allows the preparation of the composite powder with a smaller and more uniform grain size compared to the HEB technique. By adding Gr, the mechanical properties and wear resistance of the composite were much improved compared to pure Cu. In addition, the composite using the powder prepared by the ND technique exhibits the best performance with the improvement in hardness (40%), tensile strength (66%) and wear resistance (38%) compared to pure Cu. This results from the uniform grain size of the Cu matrix and the good bonding between Cu matrix and Gr. The strengthening mechanisms were also analyzed to clarify the contribution of the powder preparation techniques on the load transfer strengthening mechanisms of the prepared composite.

Herein, we investigated the effect of W content on the jet penetration performance of W-Cu shaped charge liners by using both simulation and experimental methods. The W-Cu composite liners were prepared directly by using spark plasma sintering (SPS) technique. Microstructural observations showed that W particles were uniformly dispersed within the Cu matrix. The relative density of W-Cu composites decreased slightly from 99.2% to 98.8% with an increase in the W content. The hardness of the W-Cu composite liner increased as increasing W content and reached the highest value of 209.2 HV for the composite reinforced by 60 wt.% W. Besides, the penetration depth increased and reached the maximum value of 80 mm for the composite liner containing 50 wt.% W which is improved by about 11% compared to pure Cu liner. According to simulation and experiment results, the penetration depth of the W-Cu composite liners exhibits a nearly identical trend. W-Cu composite liner containing 50 wt.% W remains the best performance compared to other composites. However, the experimental results are lower compared to the simulation results. This could be because the simulation procedure did not completely account for the actual test conditions.