Texture, morphology and deformation mechanisms in β-transformed Zircaloy-4

Intergranular Strain Evolution in a Zircaloy-4 Alloy with Basketweave Morphology

“…By associating the orientation and the shape of the oblong laths (Figure 2(c)) with the color coding in Figure 2(d), it can be seen that the interplating interface is of a h i type direction, also reported elsewhere. [9] Figure 2(e) presents pole figures for the (0001) and 10 " 10 À Á poles. The colored circles are the location of the relevant poles for several of the dominant variants present.…”

“…[6,7] The phase transformation from the b (bcc) phase to the a (hcp) phase occurs with the following Burgers relationships: {011} b plane is parallel to the close-packed (0001) a , and a nearest neighbor 1 " 11 b direction is parallel to a nearest 11 " 20 a direction. [8,9] The phase transition is believed to take place by a martensitic mechanism, exhibiting 12 equivalent lattice variants in the a phase. [8] The shape variation from b to a phase occurs via plastic deformations accommodated by the Bain strain, which involves prism slip and tensile and compressive twinning.…”

“…[8] The shape variation from b to a phase occurs via plastic deformations accommodated by the Bain strain, which involves prism slip and tensile and compressive twinning. [9,10] Given the complicated behavior of the alloy, a combination of experimental methods sensitive to crystallographic orientation, such as neutron diffraction and microscopy, need to be employed to understand the polycrystalline plasticity of such a microstructure and its implication to the material performance. Neutron diffraction is a suitable technique to correlate the bulk behavior to grains' internal strain and orientation and to measure the elastic lattice strain response to external factors (e.g., stresses and environments).…”

Hydride-Phase Formation and its Influence on Fatigue Crack Propagation Behavior in a Zircaloy-4 Alloy

“…[1,30,31] This morphology forms during the transformation from b body-centered cubic (bcc) to a (hcp) phase, by cooling from 1271.15 K (998°C) to room temperature at moderate cooling rates. [1,30,31] The prior b-Zr grains have a mean diameter of approximately 700 lm (Figure 3(a)) and each grain contains multiple a-Zr plates (Figure 3(b)). Also in Figure 3(b), the presence of second-phase precipitates can be observed that appear as white spheroids under polarized light.…”

“…[1,30,31] The presence of the second phase precipitates in the alloy's matrix can act as nucleation sites for the hydride phase. [34] Other possible trapping sites for hydrides to precipitate can be vacancies, dislocations, and microvoids as well.…”