Deformation induced twinning and phase transition in an interstitial intermetallic compound niobium boride

Interstitial compounds are widely used to improve stiffness, modulus, strength and wear resistance of alloys owing to their high strength and stiffness. Understanding defect evolution and phase transformation processes in interstitial compounds during deformation would therefore provide important guidance for further enhancement of alloy properties. Here, we observed and analyzed the various deformation-induced defects in an NbB crystal using aberration-corrected electron microscopy combined with density functional theory simulations. We identified stable defects such as stacking faults and deformation twins on {110} planes, and (020)[101] planar faults. The stability originates from preservation of the dodecahedron building blocks and B-B covalent bonds. In contrast for the case of (020)[100] planer faults, the crystal structure at planar faults is significantly altered and the B-B bonds are broken, resulting in a deformation-induced phase transition from NbB to Nb phase. These results provide insights on the deformation processes of complex interstitial compounds in general. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.