Portevin-Le Chatelier plastic instabilities: characteristics of deformation bands

Two aluminium-magnesium alloys (5182 and 5754) were investigated at room temperature. Tests were conducted on a soft tensile machine in the stress rates range where Portevin-Le Chatelier (PLC) phenomena occur. Experimental measurements on deformation bands associated with the PLC effect have shown that the band strain εb decreases with increasing stress rate σ ˙ at low values of σ ˙ . At high stress rates, however, εb increases with σ ˙ . The band propagation velocity Vb decreases with the applied stress rate. The critical strain εc for the occurrence of the PLC effect increases with increasing σ ˙ at high stress rates. At low stress rates an inverse behaviour of the critical strain is observed. All the experimental results obtained show that there is a similarity of behaviour between the critical strain εc and the band strain εb.