FCC metal-like deformation behaviour of IrNb with the L1 structure

岡本 範彦*; 竹本 昌平*; Chen, Z. M. T.*; 山口 正剛; 乾 晴行*

International Journal of Plasticity, 97, p.145 - 158, 2017/10

https://doi.org/10.1016/j.ijplas.2017.05.013

The deformation behaviour of IrNb with stoichiometric and off-stoichiometric compositions has been investigated as functions of crystal orientation and deformation temperature. The critical resolved shear stress (CRSS) for (111)[01] slip in stoichiometric IrNb exhibits a marginal temperature dependence at all temperatures with neither strong negative temperature dependence at low temperatures nor positive (anomalous) temperature dependence at high temperatures. The CRSS for (111)[01] slip exhibits orientation dependence, neither. The [01] dislocation dissociates into the anti-phase boundary (APB)-type scheme and is observed to be smoothly curved on the (111) slip plane at all temperatures, indicating the planar core structure. This is exactly what is known for the perfect dislocation in many pure FCC metals and is the reason for the observed FCC metal-like deformation behaviour of IrNb. The absence of yield stress anomaly in IrNb is discussed in terms of anisotropy in planar fault energies and elastic constants calculated by first principles calculations and experimentally determined in the present study.