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 epsilon(b) decreases with increasing stress rate (sigma) over dot at low values of (sigma) over dot. At high stress rates, however, epsilon(b) increases with (sigma) over dot. The band propagation velocity V-b decreases with the applied stress rate. The critical strain epsilon(c) for the occurrence of the PLC effect increases with increasing (sigma) over dot 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 epsilon(c) and the band strain epsilon(b). (C) 1997 Elsevier Science S.A.