The precipitation sequence of 6061Al has changed after introducing high amount SiC nanowires due to the serious segregation of Mg element. In the present work, 0.8 wt% Mg element was added into 6061Al matrix to compensate the segregation effect, and the 15 vol% SiCnw/6061Al+0.8Mg composite was prepared by pressure infiltration method. Regardless of aging time, the hardness of SiCnw/6061Al composite could be improved by the addition of Mg. MgAl2O4 phase at SiC nanowire-Al matrix interface was found in SiCnw/6061Al+0.8Mg composite after solid solution treatment. The ultimate precipitate of Al matrix in SiCnw/6061Al+0.8Mg composite has been restored from B′ (MgSi>1) to β (Mg2Si). Moreover, the hardness of composites was improved 10% after addition of Mg in the over-aging status, implying that the strengthening effect of B′ phase might be inferior to that of β' and β phases. Due to early failure behavior, the tensile strength of the peak-aged composites was slightly decreased by the addition of Mg element. However, the yield strength of the composites was improved, which could be well explained by the modified shear-lag model. It is suggested that addition of extra alloying elements to compensate the segregation effect might be an effect method to improve the yield strength. However, for the application favor high tensile strength, design of performance matching in elastic-plastic behavior between matrix and reinforcement and the ability of Al matrix to relax the stress concentration might be the advisable choice.

•W-coatings on diamond particles were prepared by the magnetron sputtering method.•W-coatings were smooth and dense on all the facets of the diamond particles.•The interfacial bonding has been significantly improved by W-coatings.•The highest TC for Al matrix composites reinforced with 100 μm diamond was obtained.•Magnetron sputtering is a successful method to prepare thin and reliable coatings.In the present work, tungsten (W) coatings with thickness range of 35–130 nm on the diamond particles were prepared by magnetron sputtering method, and then the Diamond/Al composites were prepared by the vacuum infiltration method. The prepared W coatings were smooth and dense on all the facets of the diamond particles. Moreover, the presence of W-coatings inhibited the interfacial debonding phenomenon and improved the interfacial bonding between diamond particles and Al matrix. The Diamond/Al composite with the 45 nm W-coating achieved the maximum thermal conductivity (622 W/(m·K)). To the best of our knowledge, it is the highest thermal conductivity obtained in the Al matrix composites reinforced with 100 μm diamond particles with coatings. Based on the Hasselman and Johnson (H-J) model, the thermal conductivity behavior of the Diamond/Al composites has been discussed. It indicates that the magnetron sputtering is a feasible and successful method to prepare thin and reliable tungsten coatings for the Diamond/Al composites.Download high-res image (179KB)Download full-size image

In the present work, the wire electrical discharge machining (WEDM) process of the 65 vol% SiCp/2024Al composite prepared by pressure infiltration methods has been investigated. The microstructure of the machined composite was characterized by scanning electron microscope, the average surface roughness (Ra), X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy (TEM) techniques. Three zones from the surface to the interior (melting zone, heat affected zone and un-affected zone) were found in the machined composites, while the face of SiC particles on the surface toward the outside was “cut” to be flat. Increase in Al and Si but decrease in C and O were observed in the core areas of the removed particles. Si phase, which was generated due to the decomposition of SiC, was detected after the WEDM process. The irregular and spherical particles were further observed by TEM. Based on the microstructure observation, it is suggested that the machining mechanism of 65 vol% SiCp/2024Al composite was the combination of the melting of Al matrix and the decomposition of SiC particles.

In this study, the rare earth element Y was added to Cf/Mg composite to improve the interfacial bonding strength. 60 vol% Cf/Mg composites containing different Y content were fabricated by pressure infiltration method. An interfacial layer with nano-scale formed between Cf and Mg–Y alloys. The interfacial products were identified to be MgO, Mg2Y and Mg24Y5 by energy dispersive X-ray spectroscopy (EDX) and selected area electron diffraction (SAED). Moreover, the interfacial products enhanced the interface bonding strength, which could be confirmed by the increase of interlaminar shear strength (ILSS). In particular, the Cf/Mg composite with 5.7 wt% Y addition increases the ILSS by about 120.9% from 46.2 MPa to 102.3 MPa.

•The Gd element is prone to segregate to the interface between the fiber and matrix.•Interfacial products including Gd2O3 and Mg7Gd are observed at interface.•ILSS of Cf/Mg–3.2Gd composite is increased by 60.4% compare to that of Cf/Mg composite.Matrix alloying is an effective and convenient method to improve the interface bonding strength for continuous carbon fiber reinforced magnesium matrix composites. In this work, rare earth metal Gd was selected as an alloying element to improve the interface bonding of Cf/Mg composite. Cf/Mg composites with different Gd content were fabricated by pressure infiltration method. The effect of Gd addition on the interfacial microstructures and mechanical properties of the composites were investigated. The results showed that the rare earth Gd tended to segregate at interface area to form Gd2O3 layer and particle phase Mg7Gd. Both the interfacial products enhanced the interface bonding strength which can be identified by the increase of interlaminar shear strength (ILSS). In particular, the Gd addition promoted the ILSS and bending strength greatly, with an increase by 60.4% and 25.3% compared with Cf/Mg composite, respectively. The fracture surfaces of the composites were examined by scanning electron microscopy and micrographs were employed to explain the inherent relation between interface characterization and mechanical properties.