Effects of β-cooling rates on microstructural characteristics and hardness variation of a dual-phase Zr alloy

The Effect of Cooling Rate on Crystallographic Features of Phase Transformations in Zr-2.5Nb

“…The peaks at the angles near 60 and 90° appear at the misorientation angle distribution (MAD) of the α(α′)-phase after both FC and WQ ( Figure 1 , Figure 2 c and Figure 3 c). Minor α(α′)/α(α′)-boundaries with misorientation angles of about 10° are also observed, which is consistent with the results of [ 25 ]. Such discrete α(α′)/α(α′)-MAD spectra point to the strict crystallographic limitations during the β→α(α′)-phase transformation, which, in our opinion, can only be realized by shear and shuffle mechanisms [ 50 , 51 ], i.e., with a strictly directed rearrangement of atoms during the transformation of the crystal lattice.…”

“…In general, the obtained results of the microstructure characteristics align with the findings from [ 14 , 25 , 26 ]. Some discrepancies, such as differences in alloy chemical compositions, may be attributed to the variation in experimental conditions [ 14 , 26 ], such as the superheating temperature during ST [ 25 ] and annealing in the capsule [ 14 , 25 ].…”

“…In general, the obtained results of the microstructure characteristics align with the findings from [ 14 , 25 , 26 ]. Some discrepancies, such as differences in alloy chemical compositions, may be attributed to the variation in experimental conditions [ 14 , 26 ], such as the superheating temperature during ST [ 25 ] and annealing in the capsule [ 14 , 25 ]. These factors influence both the actual cooling rates and the critical cooling rates, which affect the kinetics of the transformation processes and the size and morphology of the α(α′)-phase crystallites.…”

“…Manufacturing zirconium alloy components for nuclear reactors involves numerous thermomechanical treatments, with the resulting microstructure determining the product’s long-term and short-term properties [ 13 ]. The microstructure of Zr alloys, including local and integral texture states, crucially affects functional properties, prompting research into obtaining various microstructures through heat treatments, primarily by altering cooling rates from the β-region [ 14 , 25 , 26 ].…”

“…In [ 25 ], the study of the Zr-2.5Nb alloy demonstrated that despite variations in the morphology and size of the formed α(α″)-phases at different cooling rates, the transformation of the crystal lattice proceeds according to the Burgers orientation relationship (BOR). In this context, rapid cooling results in the realization of all 12 possible variants of the hexagonal close-packed (HCP) α-phase predetermined by the orientation of the parent body-centered cubic (BCC) β-phase grain.…”