Three-dimensional grain growth in pure iron. Part I. statistics on the grain level

Abstract

Grain evolution in pure iron is determined in three dimensions using diffraction contrast tomography at a synchrotron source. During annealing for 75 minutes at 800 • C, the evolution of initially 1327 grains is quantified as a function of 15 time-steps. A comprehensive statistical analysis is provided based on the equivalent radius, the number of faces and the mean width parameters of the grains. We introduce analytical relations between these parameters, validate them, and discuss their physical meaning. While the sample is fully recrystallized, the growth is found not to be self-similar, as evidenced in changes in the distributions of normalized grain size and number of faces per grain. More importantly, a strong decrease in the slope of the growth rate over the mean width of grain faces is observed, indicating a slowdown of grain growth. The data is used to determine the applicability of the isotropic MacPherson-Srolovitz theory to an anisotropic material such as iron. Geometrical properties that are averaged over the entire grain ensemble are well described by the model, but the properties and evolution of the individual grains exhibit substantial scatter.

Grain boundary curvatures in polycrystalline SrTiO3: Dependence on grain size, topology, and crystallography

“…In most work, H is assumed to be the inverse of the mean spherical equivalent grain radius. With the emergence of three-dimensional microscopic techniques and simulations, it has become possible to locally measure curvature within voxelized microstructures [10][11][12][13][14][15] and a technique that can be used to measure local grain boundary curvature and correlate it to the crystallography of the grain boundary has recently been reported. 16 The method has been applied to two ferrous alloys and it was found that the curvature varies strongly as a function of the grain boundary plane orientation.…”

Energetic upscaling strategy for grain growth. i: Fast mesoscopic model based on dissipation

“…Classical models (Hillert distirbution [32,33] and von Neumann-Mullins law [34,35]) are compared to the model to validate basic grain statistics. A comparison with an experimental study conducted on pure iron [36] is also presented and good agreement is observed. More detailed statistics are also analyzed to determine meaningful information to be considered at the macroscopic scale.…”

“…A recent experiment has been conducted on pure iron during annealing for 75 min at 800˚C [36]. The sample is initially fully recrystallized.…”

Characterization of metals in four dimensions

“…Recently, a comparative study using DCT and nearfield HEDM to investigate the same sample, a slightly deformed (1%) aluminum alloy with an average grain size of ∼ 100 μm, showed that DCT can detect subgrain boundaries with disorientations as low as 1 • and that HEDM and DCT grain boundaries are on average 4 μm apart from each other [110]. The unique set of key advantages of DCT-the ability to repeatedly cover large volumes (1000+ grains) in a reasonable time frame (hours) with a spatial accuracy of a few micrometers enabling extraction of experimental grain boundary characters-were exploited by Trenkle and coworkers to study 3D microstructural evolution in strontium titanate [111] and Zhang and coworkers in a study of grain growth in pure iron [112]. Zhang and coworkers measured DCT grain maps at 15 timesteps during interrupted annealing at 800 • C, with timestep 1 corresponding to the initial unannealed state and timestep 15 corresponding to 75 min.…”

“…Color represents the grain orientation along sample rolling direction (see the insert triangle), while black and white lines in (c)-(e) represent boundaries with misorientation above and below 15 • , respectively. Retrieved from Ref [112]. with permission from Elsevier.…”