Fig. 1 a X-ray diffraction pattern, b microstructure of the as-cast TiNbZrTaHf refractory alloy

Fig. 2 a Microstructure of the TiNbZrTaHf alloy after 85% reduction in thickness (the cold rolling direction is horizontal), b line profiles of the misorientation angle along the arrow AB, c pole figure of grain 1 (G1) and grain 2 (G2), d the kernel average misorientation (KAM) mapping, e boundary misorientation distribution

Fig. 3 Microstructures and grain diameter distribution histogram of TiNbZrTaHf after 85% thickness reduction and annealing at 1000 °C for a, b 1 h, c, d 4 h, e, f 24 h, g, h 500 h. Low angle boundaries (LABs) with misorientations (θ), 2° ≤ θ < 15° and high angle boundaries (HABs) with θ ≥ 15° are shown in white and black lines, respectively

Fig. 4 Invert pole figures for the normal (ND), rolling (RD) and transverse (TD) directions of TiNbZrTaHf alloys a after 85% cold-rolled and annealing at 1000 °C for b 1 h, c 24 h

Fig. 6 In-situ microstructure evolution in the cold-rolled TiNbZrTaHf alloy during continuous heating at ~ 280 K/min: a 22 °C, b 1200 °C, c 1300 °C, d 1400 °C

Fig. 7 In-situ microstructure evolution during isothermal holding at 1400 °C: a 1 min, b 2 min, c 5 min, d 10 min, e 30 min, f 60 min

Fig. 8 a-f Needlelike precipitation during isothermal holding at 1400 °C: a 22 min, b 23 min, c 24 min, d 25 min, e 26 min, f 27 min, and g EDS maps after annealing at 1400 °C for 1 h

Fig. 9 Engineering stress vs. engineering strain tensile curves of as-cast, cold rolled and annealed TiNbZrTaHf alloy. The inset shows the geometry of the tensile sample (R, radius of curvature)

Fig. 5 Microstructure of TiNbZrTaHf after 85% reduction and annealing at 1200 °C for a 1 h, b 4 h and annealing at 1400 °C for c 1 h, d 4 h

Fig. 10 SEM images of the tensile fracture surface of TiNbZrTaHf tested at room temperature: a as-cast, b, c cold-rolled, d annealed 1 h at 1200 °C

Fig. 11 Engineering stress vs. engineering strain tensile curves of a as-cast, b cold-rolled with 85% reduction, c annealed 1 h at 1200 °C of TiNbZrTaHf alloy

Fig. 12 SEM images of the tensile fracture surface of TiNbZrTaHf tested at elevated temperature: as-cast alloy at a 800 °C and b 900 °C, cold-rolled alloy at c 800 °C and d 900 °C, 1200 °C annealed 1 h alloy at e 800 °C, f 900 °C

Fig. 13 Annealed microstructures of TiNbZrTaHf alloy after cold rolling (85% reduction) for 1 h: a 800 °C, b 850 °C, c 900 °C, boundary misorientation distribution at d 800 °C, e 850 °C, f grain diameter distribution histogram

Fig. 14 Linear relationship between lnD and lnt for the grain growth at: a 1000 and 1200 °C, b 1400 °C

Fig. 15 a BSE image after annealing at 1000 °C for 500 h, b the EBSD image and c the related phase distribution, d, e BSE images after annealing at 1200 °C for 500 h and f its XRD pattern

Fig. 16 Oxidation microstructures of TiNbZrTaHf alloy at 1200 °C for 168 h: a surface, b cross-section, c EDS maps of cross-section