Powder bed fusion – laser beam of ti-6al-4v lattice structures for biomedical applications

Cao, Xue (2025). Powder bed fusion – laser beam of ti-6al-4v lattice structures for biomedical applications. University of Birmingham. Ph.D.

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Abstract

Powder bed fusion – laser beam (PBF-LB) as a technology of additive manufacturing, has provided great potential for the fabrication of porous lattice structures applied in orthopaedic devices to achieve anatomic and customised functions. However, the mechanical properties and surface characterisation involved in the osseointegration process remain challenges, causing patients risk in revision surgeries. The physiochemical properties of implants are governed by various behaviour of lattice structures and is subject to the nature of PBF-LB. To address this, the PBF-LB process need to be optimised to ensure the fabrication quality and stability of lattice structures. Fundamental understanding of lattice structures is required to satisfy wider designable possibility and improvement of mechanical and biological behaviours of skeletal devices.
First, the processing window and scanning strategy of manufacturing lattice structures with ultrafine struts thickness below 350 μm was investigated. Compared to the contour plus hatching scanning strategy, a single contour strategy was developed and optimized to ensure a more homogenous energy input for improving the geometric accuracy and internal defects reduction in lattice structures.
Secondly, performances of lattice struts with varying built angles and process parameters were studied. Both the mechanical and in-vitro biological response demonstrated the distinct impact of lattice struts angle. Results showed that under the optimised processing parameters, internal porosity can be reduced to 99.8% regardless of the geometric differences.
Considering wider feasibility of contour strategy for lattice manufacturing, multi-contour was explored to accommodate the PBF-LB fabrication of lattice structures composed with various geometries and dimensions design. Surface roughness, compressive test, and microstructures were conducted, illustrating that the ductility, surface condition and geometric accuracy and can be improved via multi-contour strategy.
At last, to further verify the potential of PBF-LB lattice structures via tailoring the struts angle, rotation strategy study was conducted and evaluated through compressive, high- cycle fatigue, and mammalian cell test. The specimen with both struts angle and unit cell orientated presents an improved fatigue strength and biological response. Overall, this thesis contributes to the development of PBF-LB lattice structures applied for biomedical implants.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):