In order to increase the strength of the joint, a novel spot welding process named walking friction stir spot welding(WFSSW) has been applied for AA 6061-T6 joints using a tool movement over a distance of 15mm. This process was carried out for four different tool rotational speeds and a better static shear strength was achieved at a tool rotational speed of 900rpm. Macro and microstructural analysis were made in order to analyze the local material microstruture evolution. The variation of microhardness in different regions of the weld was analyzed. Fatigue tests were conducted on lap-shear specimens at a stress ratio of R=0.1. Two different fracture modes were observed under both quasi-static and cyclic loading conditions. The fracture surfaces were analyzed by using optical and scanning electron micrographs

In industrial applications, welding of dissimilar metals such as aluminum (Al) and titanium (Ti) is a prerequisite for the development of hybrid components with improved mechanical and corrosion properties. However, dissimilar welding of the Al/Ti system is highly challenging due to differences in the physical and thermal properties of the two materials. In the present investigation, an attempt has been made to fabricate a dissimilar friction stir weld (FSW) of commercially pure Al and Ti and to elucidate the mechanism associated with superior joint formation. The process parameters, such as tool rotation speed, traverse speed and tool offset position have been optimized using Taguchi’s optimization technique. A detailed investigation of the weld with optimum process parameters has been carried out to reveal the mechanism of joint formation. The superior mechanical properties (24% higher ultimate tensile strength and 10% higher ductility than that of base Al) of the weld are attributed to the fabrication of a defect-free joint, formation of intercalated particles and an Al/Ti interlocking interface, homogeneous distribution of fine second-phase (Ti and/or intermetallics) particles in the weld nugget, reduction in the evolution of brittle Al₃Ti intermetallic compounds (IMCs) and recrystallization and grain refinement of Al in the weld nugget. The potentio-dynamic polarization test indicated that the optimized Al/Ti weld has ~47% higher corrosion resistance than Al; it had a very mild corrosion attack due to the homogeneous dispersion of fine particles. The method and mechanism could have an immense influence on any dissimilar weld and metal matrix composites, improving their mechanical properties and corrosion resistance.

Surface topography is a critical parameter that can influence friction and wear in engineering applications. In this study, the influence of surface topography directionality on seizure and scuffing initiation during tribological interactions is explored. Hence, unidirectional sliding wear experiments were carried out in immersed lubrication conditions for various normal loads. The tribological interactions were studied using EN31-60 HRC flats and SAE52100-60 HRC pins in a sphere on flat configuration. The results show that, in some cases, the sliding interactions in the initial cycles lead to a high friction coefficient of up to ∼0.68 in lubricated conditions, which was termed as “peak friction”, and this was accompanied by scuffing. The existence of peak friction was found to be dependent on surface topography directionality, especially when the directionality in topography was parallel to the sliding direction. Continuous ratchetting was found to be the cause of peak friction, which was accompanied by seizure and scuffing. When the topography directionality was perpendicular or independent of the sliding direction, elastic shakedown occurred at earlier cycles and prevented peak friction initiation and scuffing and also facilitated for higher steady-state friction values.