Equal Channel Angular Processing of Nickel Aluminium Bronze for Marine Platforms – University of Melbourne
Dr Cameron Barr’s research focused on enhancing the performance of nickel aluminium bronze (NAB), an alloy widely used in maritime platforms for its combination of high strength and corrosion resistance. The goal of the project was to eliminate the vulnerability of NAB to selective phase corrosion (SCC), while providing significant increases to the yield strength. In doing so, the use of NAB could be expanded to ultra-high strength applications currently filled by stainless steels, which do not share the same resistance to corrosion as NAB and risk galvanic coupling with other NAB components. Success in this project would result in enhanced capability and significant cost savings to defence through a reduction in expensive component replacements.
Equal channel angular pressing (ECAP) was used to subject ingots of NAB to extreme strains, leading to drastic reduction in grain size (from 50µm to 700 nm) and a breakdown of the lamellar phase known to cause SCC into very fine fragments (~ 350 nm). This not only prevented SCC from penetrating into the material, but also provided major strengthening through the small fragment and grain sizes, with the yield strength increasing from 275 MPa to over 950 MPa. Several models were developed to predict the yield strength and microstructure following ECAP and subsequent heat treatment. These models could be used to guide the development of new copper-based marine alloys.
Cameron’s PhD cemented his love for materials and fascination for the link between structure and mechanical properties. Cameron plans to continue his journey into the world of materials research and explore the opportunities presented by emerging technologies and techniques. Cameron hopes to further develop his analytical and modelling skills developed through his PhD and continue to use all the fantastic equipment that comes with the job.