Recrystallization textures in metals and alloys

Abstract

When a rod is drawn into wire, a bar is forged, or a sheet is rolled, the grains acquire a preferred orientation or deformation texture. When any of these are subsequently heated to a temperature high enough to create a new population of grains, this population also possesses a texture, usually though not always different from the deformation texture. The process of creation of a population of new grains is called recrystallization (since there is no change of phase, this usage differs from geologists' common usage), the treatment is called annealing and the texture is termed an annealing texture. Most annealing textures are statistically diffuse, but some (especially the (100) [001] cube texture in copper and its alloys) can be so sharp as to verge on single-crystal status. There has long been conflict between two categories of interpretation: oriented nucleation hypotheses and oriented growth hypotheses. The former assert that nuclei are generated only in particular orientations and all then grow; the latter assert that nucleation is random and that only certain orientations are able to grow fast. For a long time, attempts to decide between these were based on statistical arguments, depending on close analysis of pole figures before and after annealing. There is plenty of experimental evidence pointing to mechanisms that lead to oriented nuclei (polygonization, strain-induced grain-boundarymig-ration); and to mechanisms for oriented growth, based on the differential segregation of soluble impurities to various kinds of grain boundaries. It has become quite clear that to get an understanding of