Superplasticity of Friction-Stir Welded Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure Obtained by Warm Severe Plastic Deformation

Abstract:

High-strength sheets of Al-5.4Mg-0.2Sc-0.1Zr alloy were produced by equal-channel angular pressing (ECAP) to 12 passes via route B_C at 300 °C (573 K) followed by isothermal rolling at 300 °C (573 K) to a total thickness reduction of 80%. The final sheets with ultra-fine grained (UFG) structure were joined by friction stir welding (FSW). The tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to welding direction. The material demonstrated excellent superplastic properties in the range of temperatures from 350 (623 K) to 450 °C (723 K) at strain rates ranging from 8.3×10^-3 s^-1 to 3.3×10^-1 s^-1. The base material was found to be prone to abnormal grain growth at the testing temperature. This led to localization of the superplastic deformation in the stir zone section of the joints and thus limited total elongation-to-failure. The relationship between superplastic ductility and microstructure and application of this technique for the fabrication of large-scale superplastic sheets are discussed.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 2395-2400
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.2395
• Online since: November 2016
• Authors: Sergey Malopheyev*, Sergey Mironov, Igor Vysotskiy, Rustam Kaibyshev
• Keywords: Aluminum Alloy, Equal-Channel Angular Pressing (ECAP), Friction Stir Welding, Superplasticity, Ultra-Fine Grained Structure

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