Twin relationship in between the variant-pair of η precipitates in the Al-Zn-Mg-Cu aluminium alloy

For Al-Zn-Mg-Cu aluminium alloys, 15 types of η precipitates would possess the symmetrically variants distributed on the closed planes of the Al matrix, parallel to the (0001)η, (21̅1̅0)η, or (101̅0)η interfaces of precipitates. The η2 precipitates, possessing the crystallographic orientation of (111̅1̅)al // (0001)η2 and [110]al // [101̅0]η2, would exhibit four equivalent variants, i.e., η2(1) to η2(4), on the (11̅1̅)al habit planes. In the present work, along the zone axis of [110]al // [101̅0]η, the edge-on configurations showing the twin-like atomic arrays would occur as the growth/coalescence of two η2 variants grown on (111̅1̅)al and (11̅1)al planes, respectively. The twin relationship can be revealed in term of the crystallographic relationship at 70.5° with respect to their habit planes. Alternatively, on the (11̅1̅0)al image, it also indicates the nearly-twinning configuration in between the variant-pair of η2.

Epitaxial stabilization versus interdiffusion: synthetic routes to metastable cubic HfO2 and HfV2O7 from the core–shell arrangement of precursors

Metastable cubic HfO2 is prepared by preferential nucleation using a lattice crystallographic relationship.

SEM and TEM Characterization of NiAl2O4 Spinel Phase in Al2O3 Matrix Ni Composite

The microstructure and crystallographic relationship development of spinel phase of the composite prepared by sintering of Al2O3 and Ni powders below the melting point of Ni was investigated. Spinel phase is distributed not uniformly and the outer region of sample contains Al2O3 and NiAl2O4 without Ni particles. The differences in the microstructure between the central and surface part of the sample was clearly demonstrated. In the central part of the sample this process was only initiated and start of this reaction can be observed at the Ni/Al2O3 interface. This distribution of spinel phase is connected with the process of its formation and stability. Analysis of the crystallographic relationship between the Ni and spinel (S) indicates that the most common is the crystallographic relationship [001] S || [001] Ni or [001] S || [111] Ni. Similarly there is some statistical preference of the crystallographic relationship between spinel and Al2O3. In this case more often observed relationship is [100] S || [111] Al2O3, however similarly as in the case of Ni some deviations of several degrees are also frequent.

A Study of the γ-to-α Transformation Using EBSD Techniques

The crystallographic relationship between the g and a phases in samples of the Gibeon meteorite and a TRIP steel was investigated by means of EBSD techniques. The orientations of the two phases were measured and are represented in pole figures. The results are compared to predictions made on the basis of the Bain, Kurdjumov-Sachs (K-S), Nishiyama-Wassermann (NW), Greninger-Troiano (G-T) and Pitsch orientation relationships. The local misorientation between individual fcc and bcc crystals along their common interface was measured to demonstrate the way in which the exact orientation relationship varies along the boundary. The local orientations within lamellae and laths of kamacite and bainite are compared to that in recrystallised ferrite polygons. The occurrence of variant selection during the transformation of deformed austenite is analyzed using a recent dislocation-based model.