The effect of microbands relaxation on mechanical behaviour of prestrained copper sheets

• Type: Article in International Conference Proceedings Book
• Date: 1995

Authors

J. Grácio (Author) Other; A. Lopes (Author) Other; Manuel Vieira (Author) FEUP

Conference proceedings International

Title: 3rd International Conference on Sheet Metal

3rd International Conference on Sheet Metal - Sheet Metal¿95

University of Central England, Birmingham, UK, 26 - JUNHO - 1995

Other information

Resumo (PT): Oxygen-free DHP copper sheet has been prestrained in rolling and then deformed in tension, with the tensile axis perpendicular to the rolling direction. This sequence corresponds to an orthogonal change in strain path which has been associated with the appearance of microbands during reloading. The second test in tension was stopped at a strain of 0.06, in order to subject the samples to thermal recovery processing. The physical mechanisms occurred during recovery have been followed by transmission electron microscopy. It was shown that during recovery the microbands behave like ordinary cell structures. At a recovery temperature of 200°C, only for the initial 10 min recovery some reorganization of dislocation cells occurs. At a recovery temperature of 400°C the progress of recovery leads to the gradual decrease of the dislocation density in the cells and in the microbands. These observations allow us to conclude that the total relaxation of the microbands is only possible under dynamic recovery which evolves interaction processes between the microbands and the dislocations of non-coplanar slip systems activated as the result of grain rotation. The differences detected in the microstructural evolution at recovery temperatures of 200 and 400°C have their expression in the stress-strain curves. The mechanical behaviour of the prestrained sheet is almost not affected by the recovery process performed at 200°C. The mechanical behaviour of the sheet recovered at 400°C strongly depends on the progress of the recovery. The longer the recovery time is, the lower the yield stress becomes. Moreover, for a recovery time of 1500 min, the mechanical behaviour of the sheet is close to that of a virgin sample.

Abstract (EN): Oxygen-free DHP copper sheet has been prestrained in rolling and then deformed in tension, with the tensile axis perpendicular to the rolling direction. This sequence corresponds to an orthogonal change in strain path which has been associated with the appearance of microbands during reloading. The second test in tension was stopped at a strain of 0.06, in order to subject the samples to thermal recovery processing. The physical mechanisms occurred during recovery have been followed by transmission electron microscopy. It was shown that during recovery the microbands behave like ordinary cell structures. At a recovery temperature of 200°C, only for the initial 10 min recovery some reorganization of dislocation cells occurs. At a recovery temperature of 400°C the progress of recovery leads to the gradual decrease of the dislocation density in the cells and in the microbands. These observations allow us to conclude that the total relaxation of the microbands is only possible under dynamic recovery which evolves interaction processes between the microbands and the dislocations of non-coplanar slip systems activated as the result of grain rotation. The differences detected in the microstructural evolution at recovery temperatures of 200 and 400°C have their expression in the stress-strain curves. The mechanical behaviour of the prestrained sheet is almost not affected by the recovery process performed at 200°C. The mechanical behaviour of the sheet recovered at 400°C strongly depends on the progress of the recovery. The longer the recovery time is, the lower the yield stress becomes. Moreover, for a recovery time of 1500 min, the mechanical behaviour of the sheet is close to that of a virgin sample.

Language: Portuguese

Type (Professor's evaluation): Scientific