Muzangaza, Emmanuel (2018). The effects of titanium Ti-6Al-4V powders manufactured using electron beam melting (EBM) - additive manufacturing on metallurgical evaluation. University of Birmingham. M.Sc.
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Abstract
Multiple methods of manufacturing Ti-6Al-4V powders for Additive Manufacturing (AM) are available. The effects of the powder quality, properties and post-processing conditions on microstructure and mechanical properties in Electron Beam Melting (EBM) process are investigated in this work.
Two powders manufactured using Plasma (PA) and Gas (GA) Atomisation were fully characterised. Test specimens were built using default manufacturer’s (Arcam) parameters and mechanically tensile tested in different post-processing conditions: as built (near net-shape), heat treated using Hot Isostatic Pressing (HIP), and on surface machined. Each build specimen was cut and polished to analyse for porosity, defects, and microstructure. The microstructure of as-built samples was found to be of very fine and acicular morphology due to high solidification rate. HIP heat treatment has been observed to homogenise as-built anisotropic grain microstructure, with reduction and elimination of gas pores and defects for as-built EBM samples.
However, this (HIP) also resulted in coarser grain microstructure. Both GA and PA specimens yield strength (YS) and ultimate tensile strength (UTS) measured, with PA found to have higher values in comparison to GA. The study found that lack of fusion/un-melted particles caused lower elongation for as-built PA samples due to un-optimised parameters and process instability. Spherical gas pores (argon trapped) in GA powders and parts were predominately found due to atomisation process thus inherited in as-built parts.
Nonetheless, all samples had better and some above the minimum ASTM F294-14 titanium tensile requirement. The PA yield strength and tensile strength of the EBM as-built specimens were 850 and 925 MPa irrespectively, while GA yield strength and tensile strengths were 810 and 887 MPa irrespectively.
| Type of Work: | Thesis (Masters by Research > M.Sc.) | |||||||||
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| Award Type: | Masters by Research > M.Sc. | |||||||||
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| College/Faculty: | Colleges (2008 onwards) > College of Engineering & Physical Sciences | |||||||||
| School or Department: | School of Metallurgy and Materials | |||||||||
| Funders: | None/not applicable | |||||||||
| Subjects: | T Technology > TN Mining engineering. Metallurgy | |||||||||
| URI: | http://etheses.bham.ac.uk/id/eprint/8708 |
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