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Friction stir lap welding of the similar and dissimilar aluminum alloys is investigated. AA 5182 and AA 6022 aluminum alloys (the widely used aluminum alloys for automobile applications) are selected for the feasibility studies. The friction stir lap welding shows that the placement of the aluminum alloys in the different orders over each other affect the final weld quality and its mechanical properties. The welding parameters such as rotational and traverse speeds and the penetration depth are key factors to affect the micro-structure soundness. The mechanical and the micro-structural characterization is performed on the joints formed with varying welding parameters and from the different order of placement of the AA 6022 and the AA 5182 sheets. The weld failure occurs on the advancing side during the peel tests indicating that the retreating side is relatively stronger. Measured temperatures indicate that the advancing side has higher developed temperature during the course of welding compared to the retreating side.

Functionally graded materials (FGMs) consisting of Ni-tung (nickel-tungsten carbide) powders with different concentrations of tungsten carbide particles are successfully deposited by a laser-based direct metal deposition (LBDMD) process on 4140 steel substrates. The slurry erosion behaviour of the Ni-tung FGMs is studied at different impingement angles. The slurry erosion tests are performed at Southern Methodist University's Center for Laser-Aided Manufacturing using a centrifugal-force-driven erosiontesting machine. For the purpose of comparison, Ni-tung 40 depositions and 4140 steel samples are also tested. The results indicate that the LBDMD process is able to deposit defect-free Ni-tung FGMs with uniform distribution of tungsten carbide particles in a nickelbased matrix. The slurry erosion resistance of Ni-tung FGMs as observed to be much better than that of the Ni-tung 40 and 4140 steels. The superior slurry erosion resistance of Ni-tung FGMs is attributed to the presence of large amounts of very hard tungsten carbide particles. The material removal rate (MRR) values by erosion decrease with a decrease in the impingement angle, except at a 45 impingement angle on 4140 steel. The relationship among the MRRs, the craters' depth of penetration, the areas of the craters formed, the average surface roughness values, and the impingement angles are established for Ni-tung FGMs, Ni-tung 40, and 4140 steels. The surface profiles of the eroded samples are analysed by measuring the depth of penetration of the craters formed by the slurry jet using a needleshaped probe and a linear scale with a digital readout. The damaged surfaces are characterized by scanning electron microscopy to investigate the possible application of a material failure model, called damage initiation and damage propagation, to the case of the impingement of a mixture of solid and liquid particles on the Ni-tung FGMs, Ni-tung 40, and 4140 steels. The potentiodynamic polarization curves are generated for the three tested materials and to discover the susceptibility of the material in an erosive environment.

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