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Thesis Format

Integrated Article

Degree

Master of Science

Program

Mechanical and Materials Engineering

Supervisor

Abdolvand, Hamidreza

Abstract

Additive manufacturing (AM) is increasingly becoming one of the favourable manufacturing techniques in various industries, such as transportation and energy. The reason for the extensive use of AM lies in the ability to use a wide range of process parameters for manufacturing engineering parts with complex geometries that cannot be effectively manufactured using traditional methods such as casting or forging. Understanding the role of process parameters is crucial for developing predictive models, as well as for manufacturing engineering components with the desired properties.

This research aims to characterize the influence of AM process parameters on the deformation mechanisms of Hastelloy-X, a nickel superalloy used in gas turbine engines. In-situ neutron diffraction, electron backscatter diffraction (EBSD) and crystal plasticity finite element (CPFE) analysis are used for this purpose. The Hastelloy-X samples were printed using laser power bed fusion (LPBF) AM technique. Here, attention is given to the effects of laser power and scanning speed. First, a literature review is provided in Chapter 2, which is followed by Chapter 3 that contains a detailed description of sample preparation, experimental set-up, and data processing. The results are presented and discussed in Chapter 4. Lastly, conclusions and future works are presented in Chapter 5.

The experimental results show that the microstructure, texture, and the degree of anisotropy of the printed samples significantly change with changing AM parameters. By comparing the evolution of lattice strains predicted from CPFE to those from experiments, it is shown that {111}is the active deformation mechanism in all printed samples.

Summary for Lay Audience

A broader view of this research is to understand the deformation mechanism of additively manufactured metals. Metal components are built by depositing the raw material, which is usually in the form of powder, on a substrate and then melt this layer by using a heat source. This process is repeated layer by layer until the final part is completely built. Traditional manufacturing processes have limitations in producing parts with complex geometries or require extensive post-manufacturing processes. Such limitations are addressed in additive manufacturing by controlling, for example, the layer thickness and the depositing position. However, the mechanical properties of the final component are significantly affected by the implemented process parameters. Characterizing the influence of such paraments on the mechanical performance of the printed parts ideally means that the process can be optimized to produce a component with the best possible mechanical performance. However, such characterization is not trivial to conduct, hence, crystal plasticity numerical modeling is introduced here to conduct simulations and study the effects of the complex microstructure of the printed part. This study focuses on characterizing the influence of changing laser power and scanning speed in the laser power bed fusion process on a nickel superalloy’s texture and mechanical properties. The numerical and experimental results reveal that while the microstructure of samples changes, their deformation mechanisms stay the same.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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