Sharif Digital Repository

The effect of welding current and polarity, i.e. AC and DCEN, on imposed thermal cycles, mechanical properties, microstructural events and residual stresses was investigated in GTA welding of AA5052. A three-dimensional thermo-mechanical model was utilized to evaluate thermal responses and residual stresses distribution in the weldments. Tensile testing and hardness measurements were also conducted to study the effect of welding polarity on the mechanical properties of components. Microstructural observations utilizing optical microscopy were carried out to assess the microstructural evolutions. The results show that wide varieties of microstructures are produced in DCEN sample from cells at... 

In this study, a three-dimensional model has been utilized for predicting thermal responses during tungsten arc welding of AA2024-T4 plates in which double ellipsoidal heat source model was employed to consider the moving torch in the model. Furthermore, tensile and hardness tests and microstructural evaluations have been carried out to investigate the mechanical properties and the microstructures within the welded metal. The results show that there is a region inside the heat-affected zone where hardness increases while in some parts of this region having temperatures higher than 250 C the hardness decreases significantly. Furthermore, natural aging occurs after welding; however, its... 

Influence of gas tungsten arc welding on the thermal responses, residual stress distribution and final mechanical properties of the naturally age-hardened (T4) and artificially age-hardened (T6) AA2024 plates was studied. The results showed that age hardening and over-aging occurred in various sections of the heat-affected zone (HAZ) of T4 sample, depending on their locations, while in the HAZ of T6 sample, over-aging is the governing phenomenon. Also, subsequent natural aging occurred in HAZ, weld metal (WM) and partially melted material (PMM) of both weldments. This recent phenomenon is more obvious in the T4 sample in comparison with the T6 one. In both microstructures, weld metal is the... 

Bulk metallic glasses (BMGs), that display extraordinary properties of high strength, corrosion resistance, polymer-like formability, and excellent magnetic properties, are emerging as modern quintessential engineering materials. BMGs have garnered significant research enthusiasm owing to their tremendous technological and scientific standing. In this article, the recent advancements in the field of BMGs and their applications are put in a nutshell. Novel state-of-the-art production routes and nano/microimprinting strategies with salient features capable of circumventing the processing related complexities as well as accelerating modern developments, are briefly summarized. Heterogeneous BMG...