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Single composites are replaced by hybrid composites because of their highly efficient properties and easy processing ability. In this research work, the stir casting process has been used for the fabrication of an Aluminium 6351 metal matrix composite. The TiB2, Graphene and Rice Husk Ash (RHA) have been used as reinforcements. The various mechanical (hardness, impact, flexural, tensile) and surface (SEM, EDS, XRD) characterization have been carried out. The different samples with varying compositions of Graphene (0.0, 0.5, 1.0 and 1.5 wt.-%), the constant composition of Titanium boride (10 wt.-%) and Rice Husk Ash (2.0 wt.-%) have been fabricated. The maximum values of hardness and energy absorbed were 78.8 HV0.3 and 6 Joule respectively and minimum surface roughness of 0.308 µm have been obtained by doping 1.5 wt.-% Graphene in AA6351. Whereas, the maximum value of flexural and tensile strength was 418.73 and 154.81 MPa for AA6351 having 0.5 wt.-% of Graphene as reinforcement. Moreover, the presence of TiB2, Graphene, and RHA showed their uniform distribution in fabricated composites using surface characterization (such as SEM, EDS and XRD). [ABSTRACT FROM AUTHOR]

In this paper, a potential technique is used to weld three sheets of AA 6082 through a two-step friction stir spot welding (TSFSSW). The optimal settings of the process parameters, namely, the rotational speed of the tool, dwell time, and plunge depth during welding have been analyzed. Taguchi's L9 orthogonal array and ANOVA method is used to get proper material flow, appropriate heat conduction and the stir zone expansion, which helps in preparing sound joint. Microstructural tool analysis and fractography are performed by employing optical microscopy and Scanning Electron Microscopy (SEM). The tool was analyzed before and after use for heat effect along with the observation of the fracture behavior of the joint. To analyze the residual stresses developed in the joint, the XRD analysis is also carried out. The maximum tensile strength of 94.51 MPa was obtained under optimal parameters of the rotational speed of 1200 rpm, dwell time of 10 s, and plunge depth of 2.9 mm. The results of the ANFIS model revealed that a minor difference between experimental and model values (95.62) confirms the validation of the experiment. The resulting experimental findings of the ANFIS model were compared with other similar work done by researchers previously. [ABSTRACT FROM AUTHOR]

The structure and dynamics of water droplets on a bilayer graphene surface are investigated using molecular dynamics simulations. The effects of solid/water and air/water interfaces on the local structure of water droplets are analyzed in terms of the hydrogen bond distribution and tetrahedral order parameter. It is found that the local structure in the core region of a water droplet is similar to that in liquid water. On the other hand, the local structure of water molecules at the solid/water and air/water interfaces, referred to as the interface and surface regions, respectively, consists mainly of three-coordinated molecules that are greatly distorted from a tetrahedral structure. This study reveals that the dynamics in different regions of the water droplets affects the intermolecular vibrational density of states: It is found that in the surface and interface regions, the intensity of vibrational density of states at ∼50 cm−1 is enhanced, whereas those at ∼200 and ∼500 cm−1 are weakened and redshifted. These changes are attributed to the increase in the number of molecules having fewer hydrogen bonds in the interface and surface regions. Both single-molecule and collective orientation relaxations are also examined. Single-molecule orientation relaxation is found to be marginally slower than that in liquid water. On the other hand, the collective orientation relaxation of water droplets is found to be significantly faster than that of liquid water because of the destructive correlation of dipole moments in the droplets. The negative correlation between distinct dipole moments also yields a blueshifted libration peak in the absorption spectrum. It is also found that the water–graphene interaction affects the structure and dynamics of the water droplets, such as the local water structure, collective orientation relaxation, and the correlation between dipole moments. This study reveals that the water/solid and water/air interfaces strongly affect the structure and intermolecular dynamics of water droplets and suggests that the intermolecular dynamics, such as energy relaxation dynamics, in other systems with interfaces are different from those in liquid water. [ABSTRACT FROM AUTHOR]