Tiamiyu, Ahmed AladeUmer, Muhammad Zia ud din Urf2023-10-052023-10-052023-09-25Umer, M. Z. (2023). Evaluation of cold spray process for solid-state welding (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.https://hdl.handle.net/1880/11727510.11575/PRISM/42117Welding is an important manufacturing process used in various industries, from automotive to aerospace. However, existing welding techniques have certain drawbacks that affect weld integrity and limit their use in joining some temperature-sensitive materials. A significant concern is the heat-affected zone (HAZ), which often becomes softer than its surrounding areas. To address this problem, the expansion of cold spray process—a solid-state layer-by-layer high speed particle deposition process—as an alternative solid-state welding technique is proposed, developed, and evaluated, a process referred to as cold spray welding (CSW). As a starting point, the origin of softening in a Tungsten inert gas (TIG)-welded AA 6061-T651 plates is first comprehensively investigated using experimental, analytical, and thermodynamic modelling approaches; this is further compared with the CSWed samples to assess its (CSW) potential and current limitations for future optimization. The outcome of this study reveals that the softening effect or HAZ in the TIG-welded sample could extend up to ~40 mm from the weld center. The HAZ further partitions into four regions: HAZ1, HAZ2, HAZ3, and HAZ4, based on peak temperature, hardness, and stable precipitate phases in those regions. While the CSWed samples show several benefits: negligible microstructural alterations, inhibition of phase transformations, and suppression of deleterious HAZ, they exhibit lower tensile strength and impact toughness than TIG-welded counterpart due to the presence of ubiquitous microvoids resulting from inadequate metallurgical bonding in CSWed area. These microvoids act as initiation sites for microcracks. To guide future optimization efforts, a failure mechanism in the CSWed parts is established. This research underscores the importance of addressing softening effects in welded materials, while also charting a new path to establishing a new unexplored solid-state welding technique that has the potential to minimize the drawbacks in conventional welding methods. By understanding and overcoming the poor particle-particle/particle-substrate metallurgical bonding, CSW is poised to be an alternative greener solid-state welding technique for applications in various industries.enUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Cold spray weldingTIG weldingX-ray microscopyFracture mechanismMetallurgical bondingOxide layerMetallurgyMaterials Sciencemaster thesis