Geometrical speciality and special properties of grain boundaries

Abstract

2014 De tout temps, les utilisateurs des matériaux ont tenté de contrôler leurs microstructures dans le but de leur conférer des propriétés spécifiques pour un emploi donné. C'est de ce point de vue que cet article de synthèse considère les joints de grains, éléments fondamentaux de la microstructure polycristalline, avec deux objectifs : a) tenter d'élucider les relations entre la cristallographie d'un joint de grains, qui détermine sa structure, et différentes propriétés de ce joint ; b) établir la distribution des joints de grains dans un polycristal selon leurs caractéristiques géométriques afin de comprendre leur contribution aux propriétés de l'ensemble polycristallin.Abstract. 2014 It has long been a major preoccupation of materials users, whether implied or explicit, to tailor microstructures in order to adapt specific properties for a given application. In this context, the principal aim of the present review article is to consider the fundamental elements of polycrystal microstructures, i.e. the grain boundaries. The paper discusses current understanding of two important aspects : a) the possible relationships between the geometry of a grain boundary, which determines its structure, and its various properties ; b) the distribution of geometrical characteristics, which for real boundaries can only be approached experimentally, in an endeavour to determine the intergranular contribution to the overall properties of a polycrystal. Revue Phys. Appl. 24 (1989) 419-438 AVRIL 1989, Classification Physics Abstracts 61.70N -91.70Y -62.20 1. Introduction.

Grain boundary character distributions in Ni‐16Cr‐9Fe using selected area channeling patterns: Methodology and results

“…The published work indicates that, in general, low angle boundaries and boundaries near CSL orientations are more resistant to grain boundary phenomena, particularly those related to mechanical properties. Priester (1989) also arrives at this conclusion, but further concludes that other phenomena (e.g., intergranular diffusion and segregation) depend more on grain boundary structure determined by boundary plane orientation than on boundary misorientation. The CSL model characterizes a grain boundary as a low angle boundary (LAB), a coincident site lattice boundary (CSLB), or a general high angle boundary (GHAB) depending on the relative misorientation between the two crystals adjacent at the boundary (Pumphrey, 1976).…”

Influence of grain boundary inclination on the grain boundary and triple junction motion in Zn

“…The importance of knowing GB plane indexes in addition to the misorentation are emphasizes by several researches [4][5][6]. We observed twin GBs in Zn with the same "matrix/twin" correlation and different space orientation demonstrating dissimilar rate of motion (Fig.…”

Control of Polymorphism and Mass-Transfer in Al2O3 Scale Formed by Oxidation of Alumina-Forming Alloys

“…As mentioned above, elements such as yttrium and lutetium that were segregated at the grain boundaries of alumina by addition of only 0.05-0.1 mol% Ln 2 O 3 effectively retarded oxygen grain boundary diffusivity, creep deformation and final-stage sintering under uniform environments (Nakagawa et al, 2007, Ikuhara et al, 2002, Yoshida et al, 2002, Watanabe et al, 2003. Retardation of such mass transfer can be explained by a 'siteblocking' mechanism (Amissah et al, 2007, Cheng et al, 2008, Priester, 1989, Korinek et al, 1994 and/or grain boundary strengthening (Yoshida et al, 2002, Buban et al, 2006. Under the oxygen potential gradients used in this study, it was found that oxygen diffusitivity was unaffected by 0.05 mol% lutetia-doping (Matsudaira et al, 2010), and even for 0.2 mol% doping, the retardation was small compared to the effect in uniform environments.…”

“…On the other hand, rare earth doping can significantly increase the hightemperature creep resistance of polycrystalline alumina (Matsunaga et al, 2003, Ikuhara et al, 2001, Yoshida et al, 2002. Several studies have suggested that segregation of large dopant elements changes the grain boundary environment by 'site blocking' critical oxygen diffusion pathways (Amissah et al, 2007, Cheng et al, 2008, Priester, 1989, Korinek et al, 1994 and/or by strengthening grain boundaries by enhancing bond strengths in the vicinity of dopant ions (Yoshida et al, 2002, Buban et al, 2006). As mentioned above, when undoped polycrystalline alumina wafers were exposed to oxygen potential gradients at high temperatures, the main diffusing species depended on P O2 .…”