On the orientations of abnormally grown grains in nanocrystalline Ni and Ni–Fe

Abstract

The scanning electron microscopy-based electron backscatter diffraction technique has been used to determine grain orientations of abnormally grown grains upon annealing in nanocrystalline Ni and Ni-20 at.% Fe electrodeposits. The results show that in nanocrystalline Ni and Ni-Fe, the first grown grains that can be detected are 411 oriented with respect to the normal direction (411//ND). Upon annealing, further grain growth occurs and the dominant orientation of the abnormally growing grains changes from 411//ND to 111//ND. Twinning is found to be the mechanism responsible for the orientation change and is for the first time described in connection with abnormal grain growth in nanocrystalline materials. This means that well-known models for the formation of annealing twins (initially introduced in connection with recrystallization) also seem to apply in nanocrystalline materials.

Study of rapid grain boundary migration in a nanocrystalline Ni thin film

“…7 as an example of the distribution of twin boundaries in the material. Klement et al reported in similar studies on texture evolution in nanocrystalline Ni the development of a 1 1 4 //ND texture in the early stages of grain growth [11]. This difference in texture development may be due to a number of factors, including differences in sample composition (due to different sample synthesis methods), initial grain size, thickness, or annealing temperature.…”

“…Past in situ TEM experiments that focused on growth front velocities have suggested that this start/stop growth results from the accumulation of impurity elements at the grain boundaries [9]. Experiments on the texture development in annealed electrodeposited nanocrystalline Ni revealed the development of a 1 1 1 //ND texture via a twinning mechanism [10] with some studies also reporting an initial 1 1 4 //ND texture [11].…”

“…Examples of this instability include the observation of grain growth, including abnormal grain growth, at temperatures below 600 K in Au [1][2][3], Cu [2], Pd [4], and Ni [5][6][7][8][9][10][11][12]. The observation of abnormal grain growth has been attributed to the initial microstructure, including the distribution of the grain size, misorientation, grain boundary energy and mobility, triple junction mobility, impurities, microstrain, topological features such as curvature and number of boundary faces, etc.…”

Strain effects on annealing behaviours of moderately deformed nanocrystalline nickel

“…Previous results show that twinning is kinetically favoured over the growth of (111) oriented grains. 41 However, the role of twinning is not yet clear. Our quantitative XRD results on the planar fault probabilities of various samples are shown in Fig.…”

Characterization of multiple twinned structural units in pulse-electrodeposited nickel

“…According to literature [5][6][7], the addition of saccharin leads to the formation of fine crystallites that have a preferred <111> orientation with the growth direction (GD). But also double fibre textures have been observed in Ni and Ni-base alloys in the presence of additives: a <200> <111> double fibre texture was found for Ni with 10 and 20 nm grain size and a sulphur content of 1580 ppm and 1200 ppm, respectively [8], and a <411> <111> double fibre texture was observed in Ni and Ni-Fe electrodeposits by using X-ray diffraction and by performing measurements using electron backscatter diffraction (EBSD) technique [9]. Upon annealing, abnormal and normal grain growth sets in and the final <111> texture with respect to GD is obtained with one or two twinning operations from the initial texture of the as prepared material [8][9][10][11][12].…”