Tensile deformation behavior of aluminum alloys at warm forming temperatures

Uniaxial tensile deformation behavior of three aluminum sheet alloys, Al 5182 + 1% Mn, Al 5754 and Al 6111-T4, are studied in the warm forming temperature range of 200-350 degreesC and in the strain rate range of 0.015-1.5 s(-1). Approaches have been made to process the selected aluminum sheet alloys so that the microstructural change during warm forming provides adequate recovery favorable to formability but does not deteriorate the post-forming properties. The total elongation in uniaxial tension is found to increase with increasing temperature and to decrease with increasing strain rate. The enhanced ductility at elevated temperatures is contributed primarily from the post-uniform elongation which becomes dominant at elevated temperatures and/or at slow strain rates. The enhancement of strain rate sensitivity (m value) with increasing temperature accounts for the ductility improvement at elevated temperatures. The uniaxial tensile test is identified to serve as a screening test for ranking relative formability among different sheet alloys. Based on this criterion, the strain hardened 5xxx alloys (Al 5182 + Mn and Al 5754) have shown better formabilities than the precipitation hardened alloy (At 6111 -T4). (C) 2002 Elsevier Science B.V. All rights reserved.