Slip Bands In Single Crystals Research Articles

Slip Line Kinetics during Deformation of Cu–Al Single and Polycrystals

The formation and structure of slip lines, recorded by video during tensile deformation and supplemented by EM replica after deformation at room temperature is compared for Cu-5, 10, and 15 at% Al single crystals and polycrystals. Both show the same fine structure of slip lines in the slip bands and localization of slip increasing with solute concentration. In the first, stages of deformation, the active slip bands in single crystals are concentrated in a Luders band front propagating along the crystal length, while in the polycrystals (typical grain size up to 100 μm) the grains are activated at random along the crystal length starting with the largest grains and with preferred slip systems (mostly only 2 or 3) mostly according to Schmid's law, but activated with different succession in parts of the grains. The kinetics of single slip bands is similar in both poly- and single crystals, indicating similar elementary processes for their activation and development.

Elementary Processes in the Formation of Slip Bands in Single Crystals of α-Phase CuAl Alloys

The mechanism for the formation of slip bands by the sequential activation of internal Frank-Read sources on clusters of glide planes is widely accepted. A study of slip bands produced by plastic deformation at the yield point of single crystals of α-phase CuAl alloys provides no evidence for the operation of this mechanism. The observations lead to the conclusion that the elementary primary process in these alloys involves the generation of long-range avalanches of dislocations at opposite surfaces of the crystals on adjacent clusters of glide planes by the correlated operation of surface terrace sources. Als Mechanismus zur Bildung von Gleitbandern wird allgemein die aufeinanderfolgende Aktivierung innerer Frank-Read-Quellen auf Bundeln von Gleitebenen angenommen. Eine Untersuchung der Gleitbander, die durch plastische Verformung an der Fliesgrenze von Einkristallen aus α-CuAl-Legierungen erzeugt werden, hat jedoch keinen Beweis fur die Betatigung dieses Mechanismus erbracht. Die Beobachtungen fuhren zu dem Schlus, das der elementare Primarprozes in diesen Legierungen mit der Erzeugung langreichweitiger Versetzungslawinen an gegenuberliegenden Kristalloberflachen auf benachbarten Gleitebenenbundeln durch die korrelierte Betatigung von Oberflachenterrassen-Quellen verbunden ist.

Slip bands in single crystals of a copper-aluminium alloy etched under load

Slip bands in single crystals of a copper-aluminium alloy etched under load

The observation of slip bands in molybdenum single crystals by X-ray diffraction

The etch pit technique is a very simple method for the direct observation of dislocations and slip bands in single crystals. However, its use is often limited to certain crystallographic planes. For example, at present there is no report in the literature of an etchant which will reveal intersections on {112} planes of molybdenum. The Berg- Barrett X-ray micrography technique can be used to observe slip bands on a {112} plane. However, before using this method in studies of the growth of slip bands in molybdenum, it was deemed necessary to establish a correspondence between the X-ray contrast and the total slip band length (length of the trace containing dislocations associated with the slip band). To accomplish this goal X-ray topographs of slip bands were compared with the etch pit pattern produced by an electrolytic etchant developed by Das. These observations were made on a {124} surface of molybdenum (since the etchant does not reveal dislocation on a {112} surface).

Slip bands in single crystals of silicon iron alloys after two bendings in the opposite directions

Single crystals of iron with 3 wt. % and 7 wt. % silicon were deformed by bending after slip bands had been formed in them during the previous plastic bending in the opposite direction. The influence of the old bands on the new ones and the interaction between them have been observed.