Journal article

Formation of nanocrystalline beta structure in metastable beta Ti alloy during high pressure torsion: The role played by stress induced martensitic transformation

A Zafari, XS Wei, W Xu, K Xia



Abstract High pressure torsion was conducted to obtain nano-sized β grains in a metastable Ti-5553 alloy. Much finer grains of 100 nm in a stable Ti-20 wt.% Mo alloy. The more effective grain refinement was attributed to stress induced martensitic transformation in the former, leading to the formation of thin α" plates which divide β grains into smaller domains. Further deformation resulted in a reverse α" to β transformation with decreasing α" sizes, generating a completely nano β grain structure at very large straining. A detailed description of the β grain refinement mechanism is provided. The reverse transformation is shown to be caused by the significantly increased free energy below a ..

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Funding Acknowledgements

We are grateful to Dr. Darren Edwards of the Defence Science and Technology Organisation for conducting the HPT processing. A.Z. acknowledges the receipt of a University of Melbourne postgraduate scholarship. This investigation is partially supported by the ARC Centre of Excellence for Design in Light Metals and the Australia-China Research Centre for Light Metals.