a r t i c l e i n f o Increasing use of diffraction methods to study preferred orientation of minerals has established that quartz in deformed rocks not only displays characteristic c-axis orientation patterns, but that there is also generally a distinct difference in the orientation of positive and negative rhombs. In the trigonal quartz crystal structure positive and negative rhombs are struc...

Macroscopic strain was hitherto considered a necessary corollary of deformation twinning in coarse-grained metals. Recently, twinning has been found to be a preeminent deformation mechanism in nanocrystalline face-centered-cubic (fcc) metals with medium-to-high stacking fault energies. Here we report a surprising discovery that the vast majority of deformation twins in nanocrystalline Al, Ni, a...

Owing to its HCP crystallography, deformation mechanisms of magnesium involve both plastic slip and deformation twinning. In order to understand and ultimately to predict the mechanical response of Mg and Mg alloys, any effective continuum model should not only describe the intricate interaction mechanisms between plastic slip and twinning, but also be able to capture the different length scale...

ZK60 (Mg-Zn-Zr) alloys exhibited a variation in precipitates with aging, and their mechanical properties also changed. Microindentation tests were carried out on two types of ZK60 alloys of solid solution (T4) and peak aging (T6). Microstructure and texture evolution during indentation was investigated using electron backscatter diffraction. Twinning occurred near the indentation marks in most ...

Nanocrystalline (nc) materials can be defined as solids with grain sizes in the range of 1–100 nm. Contrary to coarse-grained metals, which become more difficult to twin with decreasing grain size, nanocrystalline face-centered-cubic (fcc) metals become easier to twin with decreasing grain size, reaching a maximum twinning probability, and then become more difficult to twin when the grain size ...

In this study, the microstructure and the mechanical properties of two new biocompatible superelastic alloys, Ti-24Nb-0.5O and Ti-24Nb-0.5N (at.%), were investigated. Special attention was focused on the role of O and N addition on α(″) formation, supereleastic recovery and mechanical strength by comparison with the Ti-24Nb and Ti-26Nb (at.%) alloy compositions taken as references. Microstructu...

Austenitic carbon steels that exhibit excellent mechanical properties due to the twinning-induced plasticity effect have been studied extensively. On the other hand, austenitic stainless steels usually achieve good strength and ductility via transformation-induced plasticity. However, relying on martensite transformation for strength may cause problems such as delayed cracking. Therefore, the t...

Ni-Mn-Ga is a ferromagnetic shape memory alloy that deforms by twin boundary motion. The magneto-mechanical properties depend strongly on the twin microstructure. A thermomechanical treatment was applied to a Ni-Mn-Ga single crystal with coexisting 10M and 14M martensite structures to create twin boundaries and align the short crystallographic c direction preferentially perpendicular to the sur...