Executive Summary : | The current engineering applications have complex parts that demand site-specific functionalities that cannot be fulfilled by a single material. Bimetallic structures offer distinct feature by combining the individual properties, that will resolve the problem of material selection issue in many industries. Titanium has excellent corrosion resistance, low density, and high strength. Aluminum alloys have low density, high strength-to-weight ratio, and low cost. By combining these two materials, a good structure can be obtained with excellent properties at relatively low cost. Fabricating the bimetallic structure of Ti6Al4V-AA2319 is very difficult by traditional methods like machining, casting, and forging due the difference in properties like melting point, and thermal conductivity, etc., An efficient alternative to manufacturing bimetallic structures is additive manufacturing, which reduces material loss. The most widely used additive manufacturing processes are powder bed fusion and wire arc additive manufacturing (WAAM). In powder-based additive manufacturing processes like selective laser melting (SLM), precise jobs can be manufactured. However, the size of the part is limited to the work area and the use of powder results in safety hazards (handling micron-size powders) with a higher price of raw materials. The WAAM can be used to manufacture bimetallic structures of large size that are near net-shaped without any hazards of handling raw materials. Hence WAAM has the advantage of reducing material loss and the ability to manufacture large parts. This project will use cold metal transfer (CMT), a variant of gas metal arc welding (GMAW), to form the bimetallic structure of Ti6Al4V-AA2319. The CMT-WAAM has lower heat input than TIG-WAAM, PAW-WAAM, and GMAW-WAAM. This may lead to reduced grain size and increase the mechanical properties of the materials. To the investigator's knowledge, few studies in the area of WAAM of bimetallic structures are present and fewer utilizing CMT-WAAM for Ti6Al4V-AA2319. However, the issue of the formation of the intermetallic in the bimetallic structure is yet to be addressed. Thus, a study of the use of CMT-WAAM in manufacturing of bimetallic structures of Ti alloy and Al alloy with change in process parameters is missing. In this study a bimetallic structure of Ti6Al4V - AA2319 will be fabricated by CMT-WAAM with reduced anisotropy. The effect of different interlayers like Niobium, Vanadium, & Molybdenum will also be investigated in this project. These interlayers should form infinite solid solutions with titanium and hinder the formation of intermetallics and enhance the microstructure and mechanical properties of the bimetallic structure. |