Deformation texture and microtexture developments in a cold rolled single phase hexagonal Zircaloy 2

Abstract

A single phase hexagonal close packed Zircaloy 2 was cold deformed to different reductions by laboratory rolling. Systematic characterisations of the structural developments were carried out. Bulk texture developments were gradual, strongest developments being noticed at the highest strain. Although formation of well defined deformation fibre(s) could not be identified, overall developments in deformation texture were best captured through Taylor type models incorporating only prismatic slip. Strain localisations were observed as single or double walled dislocation structures at approximately 45 and 60u to the rolling direction. Such strain localisations were always associated with significant lattice reorientations or misorientation developments. Relative softening in lattice strain, observed at the higher reductions, can possibly be explained by the appearance of extensive strain localisations and the associated concurrent local dynamic recovery. The grains or orientations with dominant presence of strain localisations could be indirectly related to negative textural softening.

Deformation twinning in zircaloy 2

“…2,5,[20][21][22][23][24][25][26][27] Although the existence of deformation twinning is undisputed in Zr, 2,3, there are controversies on the severity and even the existence of deformation twinning in commercial Zr alloys. 30,36,37,39,41,45 Some researchers, including the present research group*, did not report [50][51][52][53][54][55][56] significant presence of deformation twins, while others have shown 2,3, significant role of twinning in commercial Zr alloys. Such differences in the formation of twins could be attributed to the possible differences in solute, especially in interstitial, content and also on the applied strain and strain path.…”

Multipass warm/hot rolling of single phase Zircaloy 2: Developments in crystallographic texture and in lattice strain

“…34 In hexagonal systems, such as zirconium and titanium, the relative activation of slip systems 12,13 depends strongly on the working temperatures and the temptation of using different slip activations for explaining high temperature deformation texture developments is naturally understandable and often considered justifiable. 24 The present study puts a strong question on such a justification.…”

“…Classical Taylor type deformation texture simulations [18][19][20][21][22][23][24] are statistical in nature. In spite of the simplifying assumption of strain homogeneity, 18 Taylor models are successful in capturing cold deformation texture developments in cubic as well as in hexagonal systems.…”

“…In spite of the simplifying assumption of strain homogeneity, 18 Taylor models are successful in capturing cold deformation texture developments in cubic as well as in hexagonal systems. [18][19][20][21][22][23][24][25] A recent study 25 on the cold rolled Zircaloy 2 had clearly established that prismatic slip system alone, without any significant twin contributions, can predict the patterns of deformation texture developments. The use of Taylor type models for high temperature deformation is, however, more restricted.…”

“…Five thousands discretised orientations from the starting ODF, ODF of the cast and forged structure, were used for the Taylor type deformation texture simulation using full constraint (F), relaxed constraint lath (L) and pancake (P) models. [18][19][20][21][22][23][24] As shown in Table 1, different combinations of critical resolved shear stress (CRSS) ratios were used for bringing out the relative roles of prismatic (101 ¯0),112 ¯0., pyramidal (101 ¯1),112 ¯3 ¯. and basal (0001),112 ¯0.…”