Wed, 24 August, 2022
National Structural Integrity Research Centre (NSIRC) and University of Birmingham student, Alice Appleby is currently working on her PhD, jointly sponsored through an innovative new PhD model by Lloyd’s Register Foundation and TWI’s Core Research Programme (CRP).
Alice began her PhD in April 2022 on, ‘Influence of powder quality on the mechanical properties of HIPed materials for safety critical components’, and is based in both the University of Birmingham’s Advanced Metals Processing Laboratory (AMPLab) and TWI’s Thermal Processing Technologies (TPT) section at TWI Cambridge. Her supervisors for the three year duration of her PhD are Professors Moataz Attallah and Yu-Lung Chiu, and Dr Biao Cai of the University and Dr Raja Khan, Technology Consultant at TWI.
Prior to starting her PhD project, Alice completed a Master's degree in materials engineering from the University of Birmingham in 2021, during which she undertook projects in the area of sustainable manufacture of hard magnetic materials. These included a project with the Manufacturing Technology Centre (MTC), Coventry on optimising the microstructure of hot, isostatically pressed (HIPed) gamma titanium aluminide (γ-TiAl), another with the University of Birmingham’s Magnetic Materials Group on powder manufacture of NdFeB magnets, and the SUSMAGPRO project: Sustainable recovery, processing and reuse of rare earth magnets in a European circular economy, on strip casting Samarium cobalt for magnetic applications with Less Common Metals.
The CRP is designed to create new products, services, systems and processes, and expand the skills set and knowledge base of TWI and our Industrial Member companies, with the aims of improving quality, safety, reliability and operational efficiency, and reducing costs. Projects address the most significant challenges currently faced by our Industrial Members, in specific technology areas and/or industry sectors that have been identified as being of critical interest to future operations. Each project has a duration of 3 years and is focused on either engineering, materials or manufacturing technologies.
Alice’s PhD work will look into the application of hot isostatic pressing (HIPing) as a near net-shape powder manufacturing method to produce structural materials for the nuclear industry. She will investigate the influence of powder quality and processing parameters on the final microstructure and mechanical properties of HIPed materials, and use the proton and neutron irradiation facilities at the University of Birmingham to understand the effects of radiation on the HIPed material.
The first few months of Alice’s PhD have seen her begin her research on HIPing oxide dispersion strengthened (ODS) stainless steel, commonly used in the nuclear industry for piping, with nanoparticles of yttrium oxide (Y2O3) in order to increase the creep and irradiation resistance of the material. By doing this, Alice hopes to confirm and quantify any improvement in the HIPed ODS materials’ mechanical and irradiation resistant properties, and understand the effects of nano-sized Y2O3 particles on its microstructure. Subsequent plans include expanding her research into further types of ODS alloys, such as ferritic/martensitic steels and tungsten alloys, because despite these materials being contenders for nuclear fusion reactors, more data needs to be collected in order to understand how best to produce bulk-components by HIPing, as these materials are not easy to process using conventional manufacturing methods.
ODS materials are a hot topic in the nuclear industry because they are operable at higher temperatures and under greater doses per atom than un-strengthened steel, meaning they could allow reactors to run more efficiently at higher temperatures, thereby increasing the lifetime of components as a result of increased resistance to irradiation induced degradation.
In explaining some of the benefits her PhD research is expected to deliver, Alice said, “HIP is a net- to near-net shape process so the parts produced are very close in size to the desired shape, helping to eliminate expensive waste material by reducing excessive machining, whereas the use of isostatic pressure means a homogenous microstructure with reduced scatter band in the material’s mechanical properties." "By researching the HIP process we can gain a better understanding of the effect powder size distribution, HIP temperature, pressure and dwell time have on the degree of densification and, conversely, parts shrinkage.” Adding, “My hope is that my research will, ultimately, contribute to increasing the lifetime of nuclear reactors as well as making them safer and more sustainable.”
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