Controlling plastic flow in brittle structures
July 17-21, 2016
In most oxidation resistant materials, the predominant obstacle to dislocation motion is due to the changes in misfit energy as a dislocation moves, causing them to be brittle. However, at present, there is little understanding of how to design crystal structures to give easy plastic flow. Surprisingly, some hard materials deform readily, but only on a limited number of crystal planes, including ternary carbides and nitrides, such as Ti3SiC2, and compounds such as Nb2Co7, W2B5 and ζ-Ta4C3-x. Using ternary carbides as an example, it is shown that electronegativity differences within a crystal's unit cell enable dislocation line defects to move much more easily, consistent with observations in other structures. Substantial changes appear possible, suggesting that such an approach might be used as a general way of to tailoring plasticity in crystals.
R.P. Thompson, P.R. Howie, and W.J. Clegg, "Controlling plastic flow in brittle structures" in "Beyond Nickel-Based Superalloys II", Chair: Dr Howard J. Stone, University of Cambridge, United Kingdom Co-Chairs: Prof Bernard P. Bewlay, General Electric Global Research, USA Prof Lesley A. Cornish, University of the Witwatersrand, South Africa Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/superalloys_ii/59