Nanostructuring a Zr-Hf Alloy via Large Strain Rolling
A coarse grained Zr-Hf alloy has been subjected to one rolling pass with different thickness reductions ranging from 10% to 80%. Rolling was performed at three temperatures: 300°C, room temperature (RT) and liquid nitrogen temperature (-196°C). It has been found that, with increasing strain per pass, i.e., with increasing strain rate, the deformation mechanism changes from twinning to dislocation slip. The minimum strain per pass necessary to trigger the transition in deformation mechanism decreases with decreasing temperature. High strain, high strain-rate deformation leads to the development of an ultrafine grained structure. Simultaneously, a basal type rolling texture forms. At the higher temperatures (RT and above) a recrystallization texture component is also present. Thus, nanostructuring of this Zr-Hf alloy during severe rolling is attributed to a combination of grain subdivision by the formation of geometrically necessary boundaries and to nucleation and growth phenomena taking place as a consequence of rapid adiabatic heating.
T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran
M. T. Pérez-Prado et al., "Nanostructuring a Zr-Hf Alloy via Large Strain Rolling", Materials Science Forum, Vols. 539-543, pp. 2843-2848, 2007