Investigation of PLC bands with optical techniques

The Portevin-Le Châtelier effect is an interesting phenomenon that afflicts the deformation working of ductile alloys. Characteristic of this effect are the so-called PLC bands, regions of concentrated deformation that usually follow each other in a regular manner. An optical extensometer is here presented as a new measurement set-up for the investigation of these PLC bands. The optical extensometer has been employed during tensile deformation of Al-3wt.%Mg specimens and the propagation of type-B PLC bands has been detected and its velocity measured. A real-time analysis of data has been realized up to 250 scans/s, it permits to locate a deformation as soon as it emerges. This will soon make it possible to track their propagation by means of an optical sensor.