Topic：Grain boundary serration in Ni-based alloy Inconel 600: quantification, formation mechanisms & effects on mechanical properties

Speaker：Dr. Yuanbo Tang（University of Oxford）

Time：10:00-11:30，Thursday. January. 09th，2020

Venue：Room 403, Shi Chang Xu Building, IMR CAS 

Abstract:

Serration of grain boundaries in Ni-based alloys remained a curiosity for decades – when it happens the deformation mechanisms alter accordingly – yet the precise detail of the physical phenomena is still under open debate. To engineer and to control serration requires further fundamental understanding. Here we present a systematic study on serrated grain boundaries using Inconel 600, whose relatively simple composition make it a suitable candidate to elucidate its evolution. A new method based on Fourier transform aided digitised microscopy is used to analyse the multiple wave-like character of serrations. A new metric – the serration index – is devised to quantify its amplitude. A causal relationship between the serration index and heat treatment conditions has been developed, where a processing map is presented. Transmission Kikuchi diffraction & HR-TEM was used to identify the interactions between carbide & grain boundaries, which assisted to interpret two associated formation mechanisms. Furthermore, two microstructure variants – serrated and non-serrated – are tested under various conditions to exemplify the serration effect. HR-EBSD and X-ray tomography helped to assess accumulated damage by dislocation multiplications and cavitation. Consequently, the effective regime of serration is discussed.

Biography:

Dr. Tang is currently working as a postdoctoral research fellow in the University of Oxford with Prof. Roger C. Reed FREng.

He obtained his BEng Degree from Imperial College London, Materials Department with First Class Honours and ranked Top 3rd in his cohort. He skipped a Master Degree and progressed directly to a DPhil Programme in the University of Oxford, supervised by Prof Angus J. Wilkinson and Prof Roger C. Reed FREng. The project focused on Nickel-Based Superalloys, which was funded by William R Miller Scholarship and Mitsubishi Heavy Industry (MHI). He defended his Ph.D. thesis with Prof. Catherine M. F. Rae and Prof. Sergio Lozano-Perez at the age of 24. He is a member of both Micromechanics and Solid Mechanics Group.

Dr. Tang is interested in multiple aspects of Ni-based superalloys, including grain boundary engineering, advanced characterisation, deformation mechanisms, forming, alloy design and additive manufacturing. He has worked closely with a few industrial partners, including MHI, IHI, Rolls Royce, OxMet & Renishaw.

Aside science, he’s also an amateur mountaineer, marathoner, vocalist & backpacker.