Calorimetric signature of the Portevin–Le Châtelier effect in an aluminum alloy from infrared thermography measurements and heat source reconstruction

Abstract

This study is an experimental investigation of the Portevin–Le Châtelier (PLC) effect in 5052 aluminum alloy specimens. Infrared thermography and heat source reconstruction are used for this purpose. Uniaxial tensile tests at ambient temperature are first performed using macroscopic strain rates which induce type-A PLC bands. Temperature changes are measured on the specimen surface during the tests. The heat sources produced by the material are then deduced using the heat diffusion equation and a suitable filtering procedure. In addition to the calorimetric response related to thermoelastic coupling and homogeneous plasticity, mobile bands of high-intensity heat sources are revealed. The calorimetric signature of the PLC effect is analyzed with respect to the macroscopic strain rate applied to the specimen. Various microstructures are experimentally evidenced: single or multiple bands, as well as cohorts of bands forming complex X-shaped, Y-shaped and V-shaped patterns. Then, by reducing the strain rate, we focus on the heat source evolution accompanying stress serration associated with type-B bands. Heat sources related to band propagation and thermoelastic coupling during the stress drops are evidenced. Several videos illustrate the main results of this study.