The role of interfacial diffusion in the creep of Ni superalloys

I will begin by giving a very brief overview of some of my current research interests in mechanics & materials which include:
(i) mechanics of composites, especially 3D composites;
(ii) granular media; (iii) ceramics and cermets;
(iv) micro-architectured materials and
(v) cell mechanics.
The bulk of the seminar will focus on recent work on discrete dislocation modelling of the creep of Ni superalloys with an emphasis on the role of interfacial diffusion at the y / y' interfaces.

First a methodology for modelling the climb-enabled glide motion of dislocations coupled to vacancy diffusion will be presented. This includes a framework to investigate the inter-diffusion of Al in Ni₃Al at the y / y' interfaces driven mainly by the dislocation stress fields. The modelling scheme, combined with a temporal scaling algorithm, allows the modelling of the creep of these alloys on realistic time scales (i.e. on the order of 1000 hours). The experimentally observed continuously increasing creep strain rate of Ni superalloys is shown to be an outcome of this discrete dislocation model with interfacial diffusion playing a critical role. In particular, consistent with observations, the model predicts that interfacial diffusion results in the formation of wavy interfaces.

This in turn initiates the formation of dislocation cell structures in the [endif]--> phase and consequent softening of the alloy. The calculations demonstrate the critical role of interfacial diffusion in controlling the creep rates of Ni superalloys and give insight into the role heavy elements such that Re that reduce creep rates by segregating to the y / y' interfaces.

Bio:
Prof. Vikram Deshpande joined the faculty of Engineering at the University of Cambridge as a lecturer in October 2001 and was promoted to a professorship in Materials Engineering in 2010. He holds a Visiting Professorship at Eindhoven University Mechanical Engineering Department, The Netherlands. He was a tenured Associate Professor at the University of California, Santa Barbara (UCSB) in 2007-2008, and has written in excess of 200 journal articles in the experimental and theoretical mechanics solid mechanics with an h-index of 58. He serves on the editorial boards of a number of journals in mechanics and biomechanics including Journal of the Mechanics and Physics of Solids, Molecular and Cellular Biomechanics and Modelling and Simulation in Materials Science and Engineering.