Disconnection arrays in a rhombohedral twin in α-alumina

Abstract

International audienceInterfacial defects such as grain boundary dislocations are known to play an important role in the creep behavior of alumina. In the present work interfacial defects are analyzed in detail using a Volterra approach without a reference to a near-coincidence description. We investigate disconnections (boundary steps with dislocation character) in a diffusion-bonded alumina bicrystal with a misorientation close to the rhombohedral twin by conventional and atomic resolution electron microscopy. The bicrystal contains two arrays of parallel disconnections with Burgers vectors that have alternating equal and opposite twist components, so there is no long-range stress field. This configuration is discussed in terms of the stability of different grain boundary disconnection arrangements. The complex core structure of the defects is revealed by high resolution electron microscopy using exit wave reconstruction. It is shown that the defects are dissociated into two partials that delimit grain boundary segments with alternating structures

Interfaces and defects in a successfully hot-rolled steel-based composite Fe–TiB 2

“…The screw components (parallel to the [0 0 1] axis) of two close dislocations should be opposite so as to cancel long-range stress fields. Such distributions of dislocations with opposite screw components have been found for intergranular disconnections [38]. Also, the components normal to the interface plane are expected to annihilate if the ð1 0 1 0Þ TiB 2 and (1 0 0) Fe planes are strictly parallel.…”

Dislocation Structures in Low-Angle Grain Boundaries of α-Al2O3

“…In alumina, the bicrystal method, joining two pieces of single crystal at high temperature, is useful to obtain well-oriented grain boundaries [18][19][20]. So far, we have systematically fabricated alumina bicrystals with a low-angle grain boundary and characterized the dislocation structures formed in the grain boundaries by TEM [21][22][23][24][25][26][27][28][29][30][31][32].…”

Dislocation content in random high angle grain boundaries

“…Dislocation networks within GBs are difficult to study experimentally. However, some recent experimental work using TEM has been reported [68][69][70][71]. Hong et al observed networks of perfect dislocations (Burger's vector 〈110〉/2) in boundaries with small inclination to {111} planes in rolled Al [20].…”