An additive layer manufacturing (ALM) technique, electron beam melting, has been used for the production of simple geometries, from pre-alloyed Ti-6Al-4V powder. Microstructure, texture and mechanical properties achieved under standard conditions have been investigated, alongside numerical modelling of the electron beam and attempts to modify solidification through the addition of boron. Experimentation reveals an asymmetric electron beam which can be manipulated to produce different material responses. The electron beam has been used in this work, at its least powerful, as a means of preheating powder particles and, at its most powerful; to produce what is effectively a macro-scale electron beam weld. Numerical modelling and extraction of solidification parameters reveal that solidification occurs in the columnar region - columnar grains are observed experimentally and are a feature of the process. I Observed microstructures indicate a complicated thermal history that is capable of producing diffusion-less and diffusional transformation products. Electron backscatter diffraction (EBSD) and prior ~ grain reconstruction reveal a strong texture perpendicular to the build axis. Mechanical properties, tested over a range of build temperatures, are sensitive to temperature over the tested range of 625 - 700 °e. Attempts to disrupt columnar solidification via the addition of boron to Ti-6Al-4V, before subsequent EBM processing, were unsuccessful. Solidification remained in the columnar regime with no refinement in grain morphology observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555712 |
| Date | January 2011 |
| Creators | Al-Bermani, Sinan Saadi |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/14694/ |
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