Design, fabrication, and characterization of functionally graded materials
“The aim of this research was to investigate the feasibility of fabricating custom designed, graded materials using Laser Metal Deposition (LMD) that will cater for functionality and unconventional repair. The ultimate goal of the project is to establish the versatility of LMD for fabricating advanced materials and tackling problems that have been conventionally difficult or in cases infeasible. In order to accomplish these goals, this research involved investigations into, the feasibility of using elemental powders as modular feedstocks, the feasibility of fabricating tailored gradients with these custom compositions, and finally leveraging the advantages of grading materials using LMD to successfully fabricate conventionally infeasible material systems. The copper-nickel material system was chosen for demonstrating the modular feedstock concept. While the use of elemental nickel lead to porosity issues, Delero-22 a nickel-silicon-boron alloy was identified as a viable substitute. A wide range of copper-nickel alloys were fabricated through the deposition of blended powder feedstocks. Also, using these blended powder feedstocks, graded material structures of copper-nickel alloys were successfully fabricated. Varying energy input through pulse width modulation of laser power was identified as a viable means for manipulating chemistry gradient within these graded materials. The influence of varying chemistry on mechanical properties was evaluated through the use of DIC coupled mini-tensile testing. A clear distinction in the strain field indicating the spatially varying chemistry was identified during tensile testing. Also, the feasibility of depositing on highly reflective alloys of aluminum such as Al2024 and Al6061 was also investigated. Leveraging the higher absorptivity of Al4047 and remelting during LMD, a strong metallurgical bond was obtained between the substrate and the deposit. Preheating the substrate was identified to increase the reliability and quality of deposition. The bond between the substrate and deposit was found to be stronger than the deposit"--Abstract, page iv.
Additive manufacturing, Elemental powder deposition, Functionally graded materials, Laser metal deposition, Mini-tensile testing, Mechanical Engineering
Missouri University of Science and Technology
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