Microstructural and mechanical characterization of a superplastic 6xxx aluminum alloy

A new thermomechanical process has been developed which produced a fine gra in structure in an Al-Mg-Si-Cu alloy. The alloy under investigation falls w ithin the composition limits of both 6013 and 6111. The refined microstruct ure has an average grain diameter of approximately 10 mu m and an average a spect ratio near 1.6. Superplasticity was investigated using ambient pressu re, uniaxial tensile tests and cone tests with backpressure. The refined ma terial exhibits superplasticity above 500 degrees C. Uniaxial tests indicat ed a strain rate sensitivity of 0.5 at 540 degrees C, where the elongation reached 375% for a flow stress of 680 psi (4.7 MPa). Cone tests revealed ex cellent overall formability, and the suppression of cavitation with backpre ssure. The effects of strain on grain size and porosity were determined. (C ) 2000 Elsevier Science S.A. All rights reserved.