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The tribological behaviour of YG8‐cemented carbide/Ti6Al4V (YG8/TC4) contacts under aqueous lubrication was investigated in this work. Three types of nano‐additives including poly (N‐isopropylacrylamide) (PNIPAM), graphene quantum dots (GQDs), and GQDs@PNIPAM microgels were prepared for use as water lubricant additives. Tribological tests were conducted at different concentrations of nano‐additives using a ball‐on‐disk reciprocating tribometer. The experimental results show that GQDs@PNIPAM has the optimum lubricating performance, the average friction coefficient decreases by 28.7% and the average cutting wear volume of the TC4 disk increases by 29.5% when the concentration is 1.5 wt.%. This provides a new strategy for the cutting of titanium alloy materials, which not only reduces the friction coefficient, but also increases the cutting wear volume of the TC4 disk, thereby improving the machining efficiency. [ABSTRACT FROM AUTHOR]

In this paper, TiCx particles were prepared by an in situ process and added to an Al-Bi alloy, and the effects of TiCx particles on the homogenization preparation and refinement mechanism of Al-Bi alloys were studied. The TiCx particle size can be greatly reduced by decreasing graphite particle size, and the TiCx particle size was further reduced after changing C source from graphite to MLG. The TiCx particle gradually changed from angular octahedral to truncated octahedral and then became round with the C/Ti ratio increasing from 0.4 to 1.0. After the TiCx particles being added to the Al-Bi alloy, it was found that TiCx had a significant inhibitory effect on the macrosegregation and coarsening of Bi phase. The average diameter of the Bi phase decreased from 4.32 μm to 3.45 μm with the TiCx particle size decreased, and the distribution became more dispersed and uniform, contributing to the heterogeneous nucleation and self-assembly behavior of TiCx particle. With the decreasing of TiCx particle size, the refinement mechanism evolved from heterogeneous nucleation to self-assembly. [ABSTRACT FROM AUTHOR]

Featured Application: Magnetic nanoparticles can be used in a wide range of applications with the aid of an external magnetic field, such as the recycling of magnetic adsorbents, the targeted delivery of drugs, and the targeted migration of lubricant particles. If the motion of magnetic particles in fluids under the influence of magnetic fields can be accurately calculated, this will help to increase the efficiency of particle utilization and broaden particles' application areas. The present calculation starts with a model of the magnetization of magnetic particles in a magnetic field, and proposes a magnetization model for calculating magnetic forces based on the real magnetic property curves of magnetic particles. Some factors affecting the trajectory of this were further analyzed. Our calculations may serve as an important guide for targeted medicine in the biomedical field and the targeted lubrication of magnetically lubricated particles. Based on the magnetic response of magnetic particles, the targeting of particles to a target area under the modulation of an external magnetic field has been used in many applications. An accurate kinematic model is helpful to achieve accurate targeting of magnetic particles and to investigate the factors influencing the motion of the particles. In the present paper, a segmental magnetization model was proposed based on the real magnetization process of superparamagnetic particles to calculate the magnetic force, and this was compared with a traditional magnetization model. The effects of magnetic field strength and particle diameter on the trajectory of magnetic particles in fluids under a magnetic field were further analyzed using a finite element analysis software. The simulation results show that changing the particle size only affected the velocity of the particles and did not affect the trajectory. When magnetic field strength changed, magnetic particles showed different trajectories. Notably, when the magnetic field force in the Y direction was too large, meaning the gravity could be neglected, the trajectory of the particles no longer changed when the magnetic field strength was varied. [ABSTRACT FROM AUTHOR]

Abstract: A four-ball tribological test was used to investigate the effects of a TiF3 catalyst on the tribological behaviors of biofuel soot (BS)-contaminated liquid paraffin (LP). The effects of load and rotational speed were studied as well. Scanning electron microscopy with energy-dispersive spectroscopy and X-ray photoelectron spectroscopy were conducted to investigate surface element content and chemical valence state, respectively. Results showed that the extreme pressure properties of BS-contaminated LP were all promoted with or without the presence of 0.5wt% TiF3. The TiF3 catalyst material significantly contributed to the antiwear and the antifriction properties of LP with or without BS contamination. These results were caused by the decomposition of the TiF3 catalyst into TiO2 and fluoride (FeF2) which improved the lubricity. [Copyright &y& Elsevier]

Abstract: The effects of a TiF3 catalyst on the tribological behaviour of carbon black-contaminated liquid paraffin and a fully formulated engine lubricating oil (CD SAE15W-40) were investigated using a four-ball tribological test. Scanning electronic microscopy with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, surface roughness, and thermogravimetric analyses were used to investigate the surface element content, chemical valence state, surface roughness, and initial decomposition temperature of the oil samples, respectively. Results showed that the average wear scar diameter (AWSD) and friction coefficient of the two kinds of carbon black-contaminated lubricants decreased in the presence of 0.5wt% TiF3. The variation rates of the carbon black-contaminated liquid paraffin and fully formulated engine lubricating oil were 29.45% and 11.54%, respectively, and their initial decomposition temperatures decreased. These phenomena were ascribed to the decomposition of TiF3 catalyst into TiO2 and fluoride that resulted in the formation of improved boundary lubrication films. Moreover, for the fully formulated engine oil, the lubrication additive zinc dialkyldithiophosphate was catalyzed by TiF3, decomposing into polyphosphate, which aided the formation of mixture boundary lubrication films. [Copyright &y& Elsevier]