Precipitation Hardening and Corrosion Behavior of Friction Stir Welded A6005-TiB2 Nanocomposite

Abstract

Precipitation hardening and corrosion behavior of a friction stir welding (FSW) based on the aluminum alloy A6005 reinforced with TiB2 nanoparticles have been studied. Mechanical alloying (MA) and hot extrusion techniques have been employed as processing route followed by FSW. Samples characterization has been performed by DSC and TEM, and precipitation strengthening of the bulk samples and the FSW joint has been evaluated by micro-hardness tests after T6 thermal treatment. TEM characterization revealed the presence of Mg–Si hardening phases, mainly of β′ phase, and dispersoids of α-Al(FeMnCr)Si into the aluminum matrix. The results revealed that samples subjected to MA had less susceptibility to T6 thermal treatment and that the presence of nano-TiB2 reinforcement accelerates aging time. In addition, electrochemical tests based on polarization tests have been performed in 3.5% NaCl solution to assess the effect of FSW process on corrosion behavior. The FSW joint had worse corrosion behavior since the passive Al2O3 film was not generated on the weld zone. SEM–EDS analysis revealed that pits nucleated mainly in sites with a higher presence of Fe contaminant which acts cathodically with respect to the aluminum matrix, producing galvanic corrosion.