Corrosion Performance and Mechanical Strength in Aluminum 6061 Joints by Pulsed Gas Metal Arc Welding.

In this paper, the analysis of electrochemical corrosion performance and mechanical strength of weld joints of aluminum 6061 in two-heat treatment conditions was performed. The joints were produced by gas metal arc welding in pulsed mode. The original material exhibited precipitates of ß and ß" phases in a volume fraction (Vf) of 2.35%. When it was subjected to a solubilization process, these phases were present in a Vf = 2.97%. This increase is due to their change in shape and distribution in clusters within the aluminum matrix. After the welding process, the best sample in the solubilization condition reached 117 MPa, while the original material achieved 104 MPa, but all samples showed a fracture in the fusion zone. This is attributed to the heat input that produces high and low hardness zones along the heat-affected zone and the welding zone, respectively. Moreover, the change in microstructure and phase composition creates a galvanic couple, susceptible to electrochemical corrosion, which is more evident in the heat-affected zone than in the other weld regions, exhibiting uniform and localized corrosion, as was evident by electrochemical impedance spectroscopy. The heat from the welding process negatively affects the corrosion resistance, mainly in the heat-affected zone.

First principles calculations of phenol adsorption on pristine and group III (B, Al, Ga) doped graphene layers.

We studied the doping effects on the electronic and structural properties of graphene upon interaction with phenol. Calculations were performed within the periodic density functional theory as implemented in PWscf code of the Quantum Espresso package. Graphene layers were modeled using 3 × 3 and 4 × 4 periodic supercells. Doping was explored considering boron (B), aluminum (Al) and gallium (Ga) atoms. The results showed that pristine graphene and graphene doped with B atoms interacting with phenol display similar structural and electronic properties, exhibiting weak physical interactions. However, when the doping is with Al or Ga , the results are quite different. Al and Ga doping induces a stronger interaction between the phenol molecule and the doped layer, yielding chemical adsorption. In all cases, the zero gap energy characteristic is unchanged. The Dirac lineal dispersion relation is preserved in both pristine graphene and B-doped graphene.