Abstract
Non-destructive three-dimensional X-ray diffraction (3DXRD) was used to characterise the coarsening and growth of bulk crystallites in very heavily deformed aluminium in-situ during isothermal annealing. It was found that initially during the annealing, coarsening by recovery dominates. Later recrystallisation starts and, by fast growth of recrystallisation nuclei, some very big grains evolve. This occurs simultaneously with recovery coarsening of other parts of the microstructure. Consequently, very broad grain size distributions are observed. The 3DXRD results show that the nuclei (those crystallites that end up being very large by fast recrystallisation growth) do not have an initial size advantage compared to those coarsening much slower by recovery. Kinetics curves for these two categories of grains are determined. Data of this type are considered very important for understanding the thermal response of nanometals and thus also for instructing thermal treatment for optimal mechanical properties.
Acknowledgements
The authors wish to thank Drs. L. Margulies, E.M. Lauridsen, S.S. West and R.B. Godiksen for their assistance in the experiment and Drs. B. Ralph, N. Hansen, X. Huang, A.W. Godfrey and Y.B. Zhang for their comments and discussions. The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (NSFC) (Grant No. 51001016) and Danish National Research Foundation and the NSFC (Grant No. 50911130230) for the Danish-Chinese Center for Nanometals. GW would also like to acknowledge the finical support from the Young Merit Scholar of Chongqing University. ESRF is greatly acknowledged for the usage of synchrotron facilities.