AVS 65th International Symposium & Exhibition
    Advanced Surface Engineering Division Monday Sessions
       Session SE-MoA

Paper SE-MoA3
Anomalous Orientation-dependent Slip during Uniaxial Compression of TaC Crystals

Monday, October 22, 2018, 2:00 pm, Room 202C

Session: New Challenges and Opportunities in Surface Engineering
Presenter: Suneel Kodambaka, University of California at Los Angeles
Authors: M. Chen, ETH Zurich, Switzerland
D.G. Sangiovanni, Ruhr-University Bochum, Germany and Linköping University, Sweden
A. Aleman, University of California at Los Angeles
H. Zaid, University of California at Los Angeles
J.M. Wheeler, ETH Zurich, Switzerland
G. Po, University of California at Los Angeles
S. Kodambaka, University of California at Los Angeles
Correspondent: Click to Email
Binary carbides of group IV-VI transition-metals are hard, stiff, and high-melting solids with excellent high-temperature mechanical and chemical stabilities and good resistance to wear, ablation, and corrosion. Recent studies suggest that cubic B1-structured group IV and V transition-metal carbides, ZrC and TaC, are not intrinsically brittle and that they can exhibit plasticity under compression. Here, we present our results obtained using a combination of <em>in situ </em>scanning-electron-microscopy-based uniaxial micro-compression tests and <em>ab initio </em>molecular dynamics simulations conducted on TaC crystals, along with density functional theory calculations and finite-element based modeling of discrete dislocation and crack dynamics. We find that the room-temperature mechanical behavior of TaC is highly anisotropic and the operating slip systems are not necessarily those expected based on their Schmid factor. We find that the room-temperature mechanical behavior of TaC is highly anisotropic with yield strengths as high as ~17 GPa for &lt;100&gt; and as low as ~5 GPa for &lt;310&gt; crystals. Interestingly, the operating slip systems are not necessarily those expected based on their Schmid factor. We attribute the observed behavior to the normal component of the applied forces (in the direction perpendicular to the slip), whose magnitude varies with the slip plane and the crystal orientation. This anomalous slip results in the activation of {110}&lt;110&gt; slip systems during uniaxial compression of &lt;100&gt;, &lt;110&gt;, and &lt;310&gt; crystals and {111}&lt;110&gt; slip systems in &lt;111&gt; crystals and leads to the observed anisotropy in yield strengths. We suggest that similar behavior should be expected in this class of materials.