Manufacturability of porosity-gradient superelastic load-bearing structures for biomedical applications

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The proposed research activities in the field of materials science and technology are focused on the manufacturability of functionally-graded materials and structures (FGM/S) by means of the selective laser melting technique (SLM). FGM/S could be especially attractive for medical and aerospace applications. In medicine, single-piece implants with controlled transition from a porous structure favorable for bone ingrowth to a less porous load-bearing structure should reduce the risks of complications related to implant integration problems, while assuring adequate mechanical support. In aerospace, metal/ceramic FGM/S combining the high toughness, strength and machinability of metals with the heat, wear, and oxidation resistance of ceramics should result in the optimum performance of certain engine components. The present research program is mainly focused on the FGM/S’ biomedical applications, with potential extension to aerospace applications.To produce the stock metallic material, two technological routes will be explored concurrently: ingot-based and powder-based. The ingot-based route follows the common path from the melted ingot to powder through atomisation. In turn, the powder-based route implies the use of mechanical alloying (MA) of metal powders to produce the stock material of a given composition and granulometry. In the framework of this program, the significant flexibility of the MA technology in terms of alloying elements and powder size will be exploited to produce titanium alloys of target compositions. For the final product manufacturing, the SLM technique will be applied. Given the significant potential of SLM technology in terms of the process flexibility, the main focus will be on its optimisation through numerical modeling and experimentation. The following output parameters will be taken into consideration for optimizing the processing, characterization and quality control procedures: accuracy, surface finish, processing-dependant anisotropy, residual stresses, micro- and macrostructure, and static and dynamic mechanical properties. Given our long-term experience in the development, processing and application of shape memory titanium-based alloys (Ti-Ni intermetallics and near-beta Ti-Nb-X alloys), and their significant advantages as compared to other titanium alloys: superelasticity, shape restoration and enhanced damping capacity, we will maintain our focus on this group of metallic materials. To capitalize on the knowledge gained in the implementation of this research program, a real load-bearing graded-density bone substitute, such as a cervical anterior implant, will be designed, manufactured and in-vitro tested using the obtained bench-marking SLM process parameters.The results of this project, aimed at the combination of the novel additive manufacturing technologies and the high performance materials and structures, will promote the successful application of the next-generation FGM/S in medicine, and, potentially, in aerospace. Finally, the proposed program will contribute to the training of highly qualified personnel and attract top-level foreign students to Canada. They will have access to innovative technology and cutting-edge expertise in the fields of materials and novel forming processes, and will be trained within a multidisciplinary approach (materials science, metallurgy, and mechanical engineering). This enriched training will give the participating students and research personnel a competitive edge, as Canada’s booming health technology and aerospace industries are increasingly seeking personnel with this type of training.