Time: 09:00 a.m.
Place: Materials Day 2013, Ruhr-Universität Bochum, Bochum, Germany
Easo George, Oak Ridge National Laboratory, Oak Ridge, USA
Grain boundaries dominate the fracture behaviour of certain intermetallics such as Ni3Al that are ductile in single crystal form but undergo premature brittle fracture in polycrystalline form. In contrast, in certain other intermetallics such as FeAl, the relative dominance of grain boundaries depends on alloy composition (Fe:Al ratio). In both cases, however, on the transition-metal-rich side of stoichiometry, trace elements can dramatically alter the response of grain boundaries to applied stresses: strengthening them in some cases and weakening them in others. In this talk, I will review our current understanding of how trace elements such as boron and hydrogen interact with alloy stoichiometry to affect the ductility and fracture behavior of intermetallics. While the basic mechanisms are well described phenomenologically, we still lack a unified theory that can explain why certain elements are beneficial while others are harmful. This is a fundamental problem with wide-ranging implications not just in the above model intermetallic systems but also in many other structural materials.
This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.