Strain dependent rate equation to predict elevated temperature flow behavior of modified 9Cr-1Mo (P91) steel

Resisting stress for constitutive analysis of hot deformation in modified 9Cr–1Mo (P91) steel

“…The value of apparent activation energy Q was found to be in the range 369-391 kJ mol À 1 which is higher than that of lattice diffusion (Q L ¼270 kJ mol À 1 ) for g-Fe. Subsequently, it was pointed out in our previous work [13] that the observed Q can also be interpreted as Q¼380711 kJ mol À 1 . Such apparent activation energy higher than Q L for high temperature deformation is generally rationalized by considering the correction for modulus variation with temperature and further by invoking the concept of resisting stress to dislocation motion that arises due to dislocationdislocation and/or dislocation-precipitate interactions [17][18][19].…”

“…Recent studies [8][9][10][11][12][13][14][15][16] show that the sine-hyperbolic expression can be employed for predicting flow stress at different strains with the purpose of developing a strain dependent constitutive equation, because in most of the forming processes, strain is a controlling parameter. For such a strain dependent constitutive analysis in P91 steel, a new relationship between the stress multipliers of Garofalo sine-hyperbolic equation has been proposed by Phaniraj et al [15].…”

A dislocation-based model for high temperature cyclic viscoplasticity of 9–12Cr steels

“…Thus, the initial lath width is predicted to have no effect on the plastic strain range at 600 °C. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 13 0.05 α 2 3.0 Q CR [68] 400 kJ/mol D Fe,0 [69] 1.6 10 -4 m 2 /s Q δ [42] 303 kJ/mol d e [14] 6b r M23C6 [41] 45.0 nm δ 0 [15] 0.7 μm r NbC [41] 25.0 nm f M23C6 [53] 0.019 r VN [41] 20.0 nm f NbC [53] 0.001 ρ i,0 [21] 1.0 10 11 mm -2 f VN [53] 0.004 t w [21] 100 b 1.E-12…”

Constitutive modeling and dynamic softening mechanism during hot deformation of an ultra-pure 17%Cr ferritic stainless steel stabilized with Nb

“…The reason is at present unclear. Studies demonstrated that during compression tests, the increase in the average Taylor factor (i.e., increase the intensities of the "hard" (deformation) texture components) could possibly occur by increasing in strain in the absence of recrystallization This can cause some amount of hardening (textural hardening) and decrease the probability of plastic deformation [32][33][34]. As stated in the above-mentioned discussion on flow stress curves, on the one hand, DRV may be the major softening mechanism during hot deformation.…”