Identifying the character of intrinsic stacking faults in the A15 compound Nb3Al

The character of intrinsic stacking faults on {001} in the A15 intermetallic compound Nb₃Al has been investigated using energy-dispersive X-ray spectroscopy in a field-emission-gun transmission electron microscope. Line scans were obtained across edge-on faults with an electron beam of approximate diameter 0.5 nm and it was found that the Al concentration is enhanced at the fault. Taken in conjunction with crystallographic data obtained previously, this implies that a {004} layer composed of Nb atoms only is removed to form these intrinsic stacking faults in Nb₃Al. The configuration of these faults implies that they may form by Nb vacancy coalescence and could act as embryonic nuclei for the precipitation of the D8_bcompound Nb₂Al.     

Mobility of c dislocations in Ti3, Al

Abstract

The rôle of dislocations with Burgers vectors, b, given by b = [0001] during deformation of samples of the intermetallic compound Ti₃Al has been assessed. At room temperature, the experimental evidence is consistent with these dislocations being sessile, their density and morphology being similar to that in undeformed samples. In samples deformed at 650°C and above, it is concluded that motion of these dislocations is effected by dislocation climb. The line directions of the various segments of dislocations with b= [0001] are shown to be perpendicular to planes that contain sheets of Ti atoms, with an expected tendency to exhibit a high Peierls stress.     

Are you better than me? Social comparisons in carrion crows (Corvus corone)

Animal Cognition - Comparing oneself to others is a key process in humans that allows individuals to gauge their performances and abilities and thus develop and calibrate their self-image. Little...