Laser metal deposition of the Ti-5553 alloy on forged substrate for aerospace applications

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2022
Thesis identifier
  • T16288
Person Identifier (Local)
  • 201787416
Qualification Level
Qualification Name
Department, School or Faculty
  • This work aims to characterise the metallurgical properties of the Ti-5553 alloy deposited with Laser Metal Deposition (LMD) to investigate the feasibility of fabricating features on large Ti-5553 components such as the Bogie Beam. In this work, two LMD systems have been used to deposit Ti-5553 on forged and heat-treated Ti-5553 substrate under a range of various process parameters. The microstructural features have been investigated using optical and scanning electron microscopy, as well as with electron back-scatter diffraction and energy dispersive spectroscopy. Residual stresses have been evaluated using the multiple-axis contour method. Microhardness and tensile properties have been evaluated and interrelated with the underlying microstructure. Thermal modelling techniques have been used to predict the solidification conditions and thermal history of deposited components. The microstructure was shown to exhibit large columnar β-grains oriented with the build direction and columnar dendrites. The laser power was shown to influence both the β-grain size and crystallographic texture, which varied between a cube and a h001i // BD fibre. The powder feed rate was shown to influence the β-grain size and promote the existence of regions of fine equiaxed β-grains interspersed throughout the microstructure. During deposition, the development of residual heat in previously deposited layers can facilitate the β → α transformation. The microhardness in the as-deposited condition is generally low, but regions of precipitated α are significantly harder. Moderate strength and ductility was observed in the as-deposited condition. A region of tensile stresses exist adjacent to the free surfaces of the deposited blocks, while compressive stresses characterise their cores. Following sub-β-transus heat-treatment, the microhardness and tensile strength are much improved, but displays severely anisotropic ductility due to the anisotropic nature of the underlying columnar β grains. Failure in this condition is a mixed-mode of intergranular and transgranular fracture. Residual stresses are adequately relieved during the heat-treatment.
Advisor / supervisor
  • Blackwell, Paul
  • Konkova, Tatyana
Resource Type
Date Created
  • 2021