New structure in refractory high-entropy alloys

The microstructure of a new refractory high-entropy alloy of composition close to Ti35Zr27.5Hf27.5Nb5Ta5 prepared by arc melting and induction techniques was investigated using X-Ray diffraction (XRD) and transmission electron microscopy (TEM). This alloy presents optimal empirical parameters for the formation of a solid solution phase. The as-cast material displays a density of 8480 kg m(-3) and a Vickers microhardness close to 2400 MPa. While the Rietveld refinement of XRD data indicates an orthorhombic (martensite) alpha ''-type structure for the bulk alloy, TEM observations prove that the alloy exhibits a twinned hexagonal structure as thin foil. An orthorhombic-hexagonal transformation by stress relaxation during TEM sample preparation is discussed. (C) 2014 Elsevier B.V. All rights reserved.