Fig. 1 Schematic diagram of the hot compression test

Fig. 2 True stress-strain curves of the studied HNMSS under different hot compressive deformation conditions: a 0.005 s-1, b 0.05 s-1, c 0.5 s-1, d 1 s-1, e 10 s-1

Fig. 3 Linear relationship of ln$\dot{\varepsilon }$ versus lnσ

Fig. 4 Linear relationship of ln$\dot{\varepsilon }$ versus σ

Fig. 5 Linear relationship of ln$\dot{\varepsilon }$ versus ln sinh (ασ)

Fig. 6 Linear relationship of $\ln \sinh \left( {\alpha \sigma_{\text{p}} } \right)$ versus 1/T

Fig. 7 Regression analysis of the experimental data according to the hyperbolic sine constitutive equation as the function between flow stress and Z parameter

Fig. 8 Relationship between characteristic parameters and lnZ: aσp versus lnZ, bσc versus lnZ, cεp versus lnZ, dεc versus lnZ

Fig. 9 Relationship between $\ln \left[ { - \ln \left( {1 - X_{\text{drx}} } \right)} \right]$ versus $\ln \left( {\varepsilon - \varepsilon_{\text{c}} } \right)/\varepsilon_{\text{p}}$

Fig. 10 a Optical micrograph and b X-ray diffraction pattern of the sample after preheating at 1523 K for 300 s and subsequently cooling in water

Fig. 11 Microstructures of HNMSS deformed with a strain rate of 0.005 s-1 at temperature of 1223 K (a-c), 1273 K (d, e)

Fig. 12 Microstructures of HNMSS deformed with a strain rate of 0.005 s-1 at the temperature of 1373 K (a), 1423 K (b)

Fig. 13 Microstructures of the HNMSS deformed at 1423 K with a strain rate of a 0.05 s-1, b 0.5 s-1, c 10 s-1

Fig. 14 Processing maps of the HNMSS at different true strains of 0.1 (a), 0.3 (b), 0.6 (c), 0.8 (d). A and B areas marked in each figure represent the flow stability regions with peak η values

Fig. 15 Optical micrographs of the studied HNMSS deformed in the flow instability regions with the true strain of 0.6 at a strain rate of 0.5 s-1 different deformation temperatures of 1173 K (a), 1223 K (b), 1273 K (c), 1323 K (d)

Fig. 16 Microstructures of the studied HNMSS deformed in the stability region A with the true strain of 0.8 at the strain rate of 10 s-1 and different forming temperatures of 1223 K (a), 1323 K (b), 1423 K (c), 1473 K (d)

Fig. 17 Microstructures of the studied HNMSS deformed in the stability region B with the true strain of 0.6 at the strain rate of 0.005 s-1 and different forming temperatures of 1323 K (a), 1373 K (b), 1423 K (c), 1473 K (d)