“…The relationship between flow stress (σ), temperatrue (T) and strain rates ( ε ) during hot compression can be expressed by the following constitutive equations [[22]- [24]]. Effect of Grain Size and Compression Direction on the Hot Deformation Characteristics of High-Cr… 1 3 where ε is the strain rate, σ is the flow stress (MPa), T is the deformation temperature (K), A 1 , A 2 , A, n 1 , n, α and β are materials constants, Q is the activation energy (J/mol), R is the molar gas constant (8.314 J•mol −1 •K −1 ), Z is the Zener-Hollomon parameter.…”