Grain Growth in Nanocrystalline Nickel

Abstract

In this study, the effect of grain size distribution on the thermal stability of electrodeposited nanocrystalline nickel was investigated by pre-annealing material such that a limited amount of abnormal grain growth was introduced. This work was done in an effort to understand the previously reported, unexpected effect, of increasing thermal stability with decreasing grain size seen in some nanocrystalline systems. Pre-annealing produced a range of grain size distributions in materials with relatively unchanged crystallographic texture and total solute content. Subsequent thermal analysis of the pre-annealed samples by differential scanning calorimetry showed that the activation energy of further grain growth was unchanged from the as-deposited nanocrystalline nickel.

Grain boundary migration during abnormal grain growth in nanocrystalline Ni

“…6 presents the same at 693 K after annealing times of ∼1, 30, and 3600 s. Relatively large grains in the size range of 100-1000 nm were observed in a nanocrystalline matrix after very short annealing times (Figs. 5a and 6a) and were similar to those observed in previous ex situ annealing studies [10,11,13,14]. The nanocrystalline matrix was consumed after 3600 s at 593 K and 30 s at 693 K, resulting in a uniform microstructure having a mean grain size on the order of ∼350 nm.…”

“…It is likely that a thin foil effect was responsible for this stabilizing behaviour, considering that it has not been observed in any bulk ex situ annealing experiment of nanocrystalline Ni produced by the same synthesis method (e.g. [10,11,13,14]). It is well established that the artificial free surfaces of a TEM foil can introduce a pinning effect which inhibits grain boundary migration [19].…”

“…[9][10][11][12][13][14]). Calorimetric studies have shown a broad, low energy exotherm followed by a main heat release peak [10], having an activation energy similar to that of grain boundary self-diffusion [11].…”

“…Calorimetric studies have shown a broad, low energy exotherm followed by a main heat release peak [10], having an activation energy similar to that of grain boundary self-diffusion [11]. Transformation mechanisms have generally been inferred by characterizing annealed microstructures and tracing the structural evolution back to the initial state [9][10][11][12][13][14]. This approach has shown that the structure initially undergoes pronounced abnormal grain growth in which a few growth centers become activated, consuming an otherwise stable nanocrystalline matrix [10,11].…”

Individual grain orientations and texture development of nanocrystalline electrodeposits showing abnormal grain growth

“…In previous investigations of Ni and Ni-alloys, a 2 0 0 1 1 1 double-fiber texture was found at the surface facing the substrate in the plating process [1,8,[18][19][20][21][22][23][24]. Consistently, an increase of the 1 1 1 //ND component at the expense of the 2 0 0 //ND component was found upon annealing, i.e.…”