Aa

Effect of deformation temperature on grain refinement in alpha titanium alloy VT5-1

“…The curves exhibited an initial hardening transient, flow softening at high deformation temperatures and steady-state flow stage (σ ss ). Such type of curves is typical for hot and warm deformations at which dynamic recovery and recrystallization take place [9][10][11][12].…”

“…The mean size of grains/subgrains (D/d), which were formed in the alloy during deformation, obeys a powerlaw of the steady-state flow stress [9][10][11][12]. The empirical relationship can be expressed as…”

“…, where μ is temperature dependent shear modulus of the alloy and N is the grain size exponent [10][11][12]. Relationship between the mean size of α-grains/subgrains and the steady-state flow stress normalized by shear modulus for VT5-1 alloy is given in Figure 3a (the value of shear modulus at room temperature was taken from Ref.…”

“…The relationship D-σ ss /μ consisted of two lineal parts. The value of N (N shows inclination of the lineal part of the function) was 0.93 for the part corresponding to lower stresses and coarser grains that is typical for discontinuous dynamic recrystallization [4,5,[9][10][11][12]15,16]. The value of N for the lineal part corresponding to higher stresses and smaller grains was 0.31 indicating continuous dynamic recrystallization [4,5,15,16].…”

“…The mean subgrain size was approximately two times smaller than the mean grain size after deformation at 940-840°C, and those sizes became closer after deformation at 750-650°C. Essential difference in grain and subgrain sizes is typical for discontinuous DRX [5,[9][10][11][12][15][16][17], whereas the small difference in these sizes and higher dislocation density indicates the occurrence of continuous DRX at which migration of high-angle boundaries is impeded [5,[15][16][17][18].…”