## Li et al studied the hot deformation behavior of extruded

Fig.?2. Initial microstructure of Go 6976 experimental alloy: (a) transverse direction; (b) extrusion direction.Figure optionsDownload full-size imageDownload as PowerPoint slide

Fig.?3. XRD pattern of the experimental alloy.Figure optionsDownload full-size imageDownload as PowerPoint slide

3.2. Flow stress behavior

Fig.?4. True stress–true strain curves for the experimental alloy under different conditions: (a) ε? = 0.001 s−1; (b) ε? = 0.01 s−1; (c) ε? = 0.1 s−1; (d) ε? = 1 s−1.Figure optionsDownload full-size imageDownload as PowerPoint slide

Fig.?5. The variation in peak flow stress with temperature under different strain rates.Figure optionsDownload full-size imageDownload as PowerPoint slide

3.3. Constitutive equation

To further investigate the hot deformation behavior of the extruded alloy, the constitutive characteristics were studied, and the forging and extrusion force can be predicted using the determined constitutive equations. A hyperbolic sine–type equation (Eq. (1)) is generally used to describe the relationship among deformation parameters for a wide range of stresses [17] and [18]:equation(1)ε?=Asinh(ασ)nexp(-Q/RT)where σ is the flow stress, Q the activation energy of deformation (kJ/mol), T the absolute temperature (K), R is the universal gas constant (8.314 J/K), and A, n and α are the material constants independent of σ and T. When the flow stress is low (ασ < 0.8), Eq. (1) can be simplified according to exponential law [19] toequation(2)ε?=A1σn1exp(-Q/RT)