Deformation behavior of a Ni3Al(B,Zr) alloy during cold rolling: Part II. Microstructural and textural changes

Part I of this study described the changes in order and of structure during cold rolling of a Ni₃Al(B,Zr) alloy. The textural and microstructural changes that occur during deformation are reported in this part. In addition to other features, a high density of shear bands start forming in this alloy from a rather early stage of deformation. The cold rolling texture of the material, which is basically of pure metal type at low strain levels, changes into alloy type after rolling between 35 and 45 pct. The maximum pole density of the alloy type texture is obtained at the {168}〈211〉 location. Transmission electron microscopy (TEM) micrographs show the presence of twins in the material from a deformation level of 35 pct onward, their density increasing with increase in deformation level. As has been proposed earlier, a structural transformation from L1₂ to DO₂₂ appears to take place in the γ′ phase during rolling. This will change the deformation mode from primarily slip to twinning and this could be responsible for the observed textural change with rolling. The γ phase deforms by slip in a manner similar to a fcc material with high stacking fault energy. The final texture of the material actually reflects an aggregate of the components developed in the two phases.