Selective laser melting (SLM) to fabricate Al0.5CoCrFeNi high entropy alloys with pre-mixed powders was studied in this paper. The influences of process parameters including laser power, scanning speed, and hatch spacing on the relative density of high-entropy alloys (HEAs) were investigated. A relative density of 99.92% can be achieved by optimizing the SLM process parameters with laser power 320 W, scanning speed 800 mm/s, and hatch spacing of 60 μm, respectively. Moreover, the microstructure of the HEAs was also studied using scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was found that the microstructure of the HEAs was only composed of face-centered cubic and body-centered cubic phases, without complex intermetallic compounds. The mechanical properties of the HEAs were also characterized. At ambient temperature, the alloys had a high yield strength of about 609 MPa, tensile strength about 878 MPa, and hardness about 270 HV. Through a comparison with the corresponding alloys fabricated by vacuum induction melting, it can be concluded that the high entropy alloys fabricated by SLM had fine microstructures and improved mechanical properties.

Morphology of CF before and after grafting CNT; wear resistance of CF/EP composite.

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A novel lubricating material of hierarchical carbon fiber-MoS 2 ultrathin nanosheets (CF-MoS 2 ) was fabricated by one-step hydrothermal solution reaction method. The corresponding phase composition, morphology and formation mechanism were systematically determined by XRD, FESEM and TEM. And the effects of CF-MoS 2 on the tribological properties of epoxy (EP) were investigated comparatively using universal micro-tribotester-2 (UMT-2). Results showed that MoS 2 ultrathin nanosheets with the thickness of 5-8nm and size of 300-500nm were synthesized successfully. And several MoS 2 nanosheets assembled together in flower-like shape and were attached onto CF surface uniformly. Furthermore, the XRD pattern analysis of as-prepared CF-MoS 2 confirmed that MoS 2 was in the form of hexagonal phase. Besides, the shore hardness of EP matrix was improved obviously by the incorporation of CF-MoS 2 , suggesting the load-carrying capacity of EP was enhanced. More importantly, EP/CF-MoS 2 composite had much better tribological properties than EP and other EP-based composites (EP/CF and EP/MoS 2 ) 2 because of the reinforcement effect of CF and lubricating effect of MoS 2 . In particular, EP/CF-MoS 2 composite still possessed good friction-reducing and anti-wear properties under heavy loads. Namely, hierarchical CF-MoS 2 was a promising additive to be used in tribology field.

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