Graduation Semester and Year
Fall 2024
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Amir Ameri
Second Advisor
Paul Davidson
Third Advisor
Miguel Amaya
Fourth Advisor
Robert Taylor
Fifth Advisor
Emma Yang
Abstract
Laser Powder Bed Fusion (LPBF) is a cutting-edge additive manufacturing process that enables the fabrication of complex metal components with high precision and design flexibility. In existing research, much of the focus in LPBF has been on improving part quality by reducing process-induced defects and controlling microstructural evolution. The present work aims to explore how modifications in LPBF process parameters can enable the creation of components with spatially tailored mechanical properties while using a single feedstock material. Specifically, this study investigates how localized process modifications can influence the microstructure and mechanical properties of Ti-6Al-4V, a widely used titanium alloy.
During LPBF, the cooling rate following the laser melting process plays a critical role in determining grain size, with faster cooling rates generally resulting in finer grains. In this study, the cooling rate of material points within the part was modified by implementing a local double melt strategy, a technique that involves reprocessing selected regions within each layer. The goal was to induce localized reinforcement by modifying the thermal gradient and cooling rate in specific areas of the build.
Ti-6Al-4V specimens were fabricated using a single feedstock material, with the predefined local double melting strategy applied within each layer to achieve tailored properties. Tensile testing was performed to evaluate the bulk mechanical properties of the material, including yield strength, ultimate tensile strength, and elongation. The study also focused on Vickers hardness measurements at various positions within the samples to assess the effect of localized reinforcement on hardness variation across the part. Additionally, fracture toughness was evaluated by analyzing the material's resistance to crack propagation, particularly in regions influenced by the localized thermal gradients.
The results revealed that the integration of the local double melting strategy significantly impacted both the microstructure and mechanical properties of the Ti-6Al-4V specimens. Variations in grain size were observed, with areas subjected to double melting exhibiting finer grains than regions exposed to single melt processing. Hardness values showed an increase of up to 10% over Double Exposed region, while tensile testing demonstrated a 40% improvement in elongation and 5% enhancement in crack arresting behavior, indicating improved ductility and fracture toughness.
These findings highlight the potential of the localized double melting strategy to create Ti-6Al-4V components with spatially tailored mechanical properties. This technique has significant potential in industries such as aerospace, where the ability to create components with enhanced strength, ductility, and fracture resistance in specific regions is crucial. The results underscore the promising capability of LPBF to produce components with distinctive behaviors, resembling composite materials, through strategic process modifications.
Keywords
Additive Manufacturing, Ti6Al4V, LPBF, Powder Bed Fusion, Reinforcements, Composite, Microstructure, Mechanical Properties, Fracture Toughness, Metal AM
Disciplines
Manufacturing | Metallurgy | Other Mechanical Engineering
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Ganesh-Ram, Aditya, "IN-SITU LOCALIZED REINFORCEMENT IN TI6AL4V ALLOY VIA LASER POWDER BED FUSION PROCESSING" (2024). Mechanical and Aerospace Engineering Dissertations. 422.
https://mavmatrix.uta.edu/mechaerospace_dissertations/422