Abstract:

The first part of the talk will be on the challenges and the potential solutions of titanium (Ti)-based alloy processing through Additive Manufacturing (AM), also known as 3D printing. AM, which allows the realisation of a metallic component with complex geometries not achievable by conventional production methods in a single step, is currently leading a significant change in the aerospace and biomedical industries. It is estimated that up to 50% production savings can be obtained for Ti-based components with flexible design and increased customisation. Major limiting factors of AM Ti-parts are inferior fatigue resistance (porosity), metastable phases / residual stresses and the lack of homogeneity in their as-built microstructure, which dictates the application of post-processing heat treatments. Most significant α+β Ti-alloy, Ti-6Al-4V (Ti64), dominating the Ti market with more than 50% of the overall production, suffer from directional thermal gradient of the melt pool, which prevents the nucleation ahead of the solidification front resulting in coarse, columnar prior β grains with strong crystallographic texture along the building direction. Upon rapid solidification, columnar prior β grains transform to martensitic-α’ phase with a Burgers orientation relationship (OR), leading to poor mechanical properties. As a result, AM Ti64 possesses lower ductility and fatigue performance compared to wrought Ti64, making the AM process less competitive.

The final part of the talk will focus on the low-temperature AM of bioresorbable magnesium (Mg) implants. The use of biodegradable Mg alloys has the potential to improve patients’ quality of life by avoiding the necessary secondary operations conducted regularly for the removal of implants fabricated from conventional non-resorbable alloys. Having excellent biocompatibility and biodegradability along with a low modulus of elasticity (decreased bone-shielding) lead to clinical uses as bone-fixation screws (Magnezix®, Syntellix) and coronary stents (Magmaris®, Biotronik). Next generation Mg implants necessitate patient-specific designs which can be realised most effectively via AM. However, AM processes based on Powder Bed Fusion (PBF) have not been widely adopted for Mg-alloys due to safety concerns arising from the intrinsic properties of Mg, such as high affinity to oxygen, low boiling temperature and high vapour pressure. Fused Deposition Modelling (FDM) is a cost-efficient 3D-printing technique commonly used to produce polymer-based components. Employing FDM that operates at low temperatures (<200˚C) can offer key technological advancement in the customisation of patient-specific Mg alloys with maximum design flexibility. The key limiting factor is the low sinterability of Mg and its alloys

Bio:

Dr. Mert Celikin is an Associate Professor at the School of Mechanical and Materials Engineering in University College Dublin, Ireland. He received his PhD in Materials Engineering at McGill University (Canada) in 2012, where he studied high temperature deformation behaviour of magnesium (Mg) alloys for automotive powertrain applications. He has worked as a postdoctoral fellow at McGill Metals Processing Centre and Institut National de la Recherche Scientifique – Centre Énergie Matériaux Télécommunications (INRS-EMT). His research at INRS-EMT was on advanced self-healing composites and optical fibre-based devices for aerospace/space applications with international / industrial collaboration (European Space Agency (ESA), Netherlands and MPB Technologies Inc., Canada). He was awarded prestigious Marie-Sklodowska Curie Fellowship (2021-2023) and Research Ireland (formerly Science Foundation Ireland) Frontiers for the Future grant to continue his research on the design and processing of biodegradable Mg alloys via novel additive manufacturing (AM) technology. His current research focuses on designing and processing novel alloy compositions with superior fatigue resistance and more compatible with AM for biomedical and aerospace applications. Industrial collaboration with multinational biomedical companies, including Boston Scientific, Stryker and Croom Medical. Dr. Celikin is a Funded Investigator (FI) in I-Form, SFI Research Centre for Advanced Manufacturing and the UCD Coordinator for the Centre for Doctoral Training (CDT) in Advanced Metallic Systems in partnership with the University of Manchester, the University of Sheffield, UCD and DCU. Dr. Celikin has been the Program Director for ME in Materials Science and Engineering since 2019.