Papers by Author: Jacob R. Bowen

Abstract: The effect of large strain deformation on microstructural refinement has been intensely investigated by many deformation processes. Two popular processes are equal channel angular extrusion (ECAE) and accumulative roll-bonding (ARB). This work presents the evolution of microstructure in Al-0.13%Mg as a function of von Mises strain for both ECAE and ARB in terms of high and low angle boundary spacing and relative fraction, as well as the stability of the deformed structures after a strain of 10, thereby allowing a direct comparison of the two processes. It is found that microstructural evolution as a function of strain is similar, and that ARB structures after a strain of 10 are more stable than ECAE on annealing.

Abstract: Severe deformation techniques allow metallic alloys to be deformed to ultra-high plastic strains, without any geometrical change to the work piece. They thus offer potential for the cheap production of submicron grained materials, in a bulk form. After processing severely deformed materials do not have conventional, idealized, grain structures, contain significant fractions of low angle boundaries, and are often heterogeneous. Due to their high stored energy, they are unstable on annealing and in most cases can be thought of as continuously recrystallizing. However, locally discontinuous behaviors are often observed, due to the retained less mobile low angle boundaries, as well as abnormal grain growth at elevated temperatures. Monte-Carlo-Potts models have been used to show the sensitivity of the annealing behavior to the initial starting structure present after deformation. The effect of coarse (~1µm) particles and fine dispersoid particles are also discussed.

Abstract: Possible variations in recrystallization kinetics from the sample surface to the center have been investigated in 90% homogeneously cold rolled aluminium (AA1050). It was found that whereas the average growth rates are quite similar, the nucleation characteristics are different at the surface and in the bulk.