THE SUPERPLASTICITY OF COMMERCIAL ALUMINUM-ALLOY

In this work the superplasticity of cold-rolled sheet metal of LF6 aluminium alloy has been studied. An extremely significant superplastic effect has been attained in the cold-rolled condition without any special pre-treatment. A total elongation as high as 463% has been achieved under the following conditions: 490°C and 3.33 × 20-1 s-1, where the corresponding strain rate sensitivity index m = 0.68 and the flow stress σ = 2.8 MPa. As compared with data available in the international literature, the above results are pre-eminent. The results of mechanical testing and metallographic examination indicate that the presence of particles of the second phases such as β (Mg2Al3), MnAl6 and TiAl3 leads to the formation of the fine and stable grains necessary for the achieving of superplasticity. The most probable deformation mechanism for the superplastic flow of LF6 aluminium alloy is grain boundary sliding accomodated by sliding within grains. The results presented in this paper may lead to the incorporation of the pre-treatment necessary for superplastic forming of certain alloys in the primary working process. As a result, superplastic forming processes would be simplified and the application of this new technology to industry could be expanded. The achievements of this study have been put into practice and the results are excellent. The authors have made some suggestions to the metallurgical industry in order that the present findings can be implemented as soon as possible. © 1990.