Some aspects of Portevin-Le Chatelier plastic instabilities investigated by infrared pyrometry

The deformation heterogeneity related to the Portevin-Le Chatelier effect has been studied for aluminium-copper alloy during a tensile test at ambient temperature. Plastic deformation is accompanied by dissipation of mechanical energy into heat. To observe the localization of deformation in bands, we used a pyrometer coupled to an infrared camera. This device serves to visualize the formation of the deformation bands and to quantify apparent velocity. From these thermal data, we can also determine the geometrical characteristics of the bands: orientation, bandwidth, and space between two bands. The aperture time (1500 μs) and the acquisition frequency of the camera (60 Hz) allow the band-formation time and the middle-band time to be estimated. The measurement of the variation in temperature during the appearance of a band is used to quantify the plastic deformation in the band.