Superplastic Behavior of Friction-Stir Welded Joints of an Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure

Abstract:

The commercial Al-5.4Mg-0.2Sc-0.1Zr alloy was subjected to equal-channel angular pressing at 300°C to a true strain ~12 followed by cold rolling to a total thickness reduction of 80%. The ultrafine-grained sheets were joined by friction stir welding (FSW). To evaluate superplastic properties of the weldments, the tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to the welding direction and pulled up to failure in the temperature range of 400 to 500°C and at strain rates of 2.8×10^-4 s^-1 to 5.6×10^-1 s^-1. The friction-stir welded material exhibited excellent superplastic properties. The highest elongation-to-failure of ~1370% was recorded at a temperature of ~450°C and an initial strain rate of 5.6×10^-2 s^-1, where the strain rate sensitivity coefficient was about 0.64. The relationship between superplastic ductility and microstructure is discussed.

• Periodical: Materials Science Forum (Volumes 838-839)
• Pages: 338-343
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.838-839.338
• Online since: January 2016
• Authors: Sergey Malopheyev*, Sergey Mironov, Igor Vysotskiy, Rustam Kaibyshev
• Keywords: Aluminium Alloy, Equal-Channel Angular Pressing, Friction Stir Welding, Superplasticity, Ultrafine-Grained Structure

References

[1] I.J. Polmear, Light Alloys: From Traditional Alloys to Nanocrystals, 4th ed., Butterworth-Heinemann/Elsevier, UK, (2006).

DOI: 10.1017/s000192400008670x

[2] K.L. Kendig, D.B. Miracle, Strengthening mechanisms of an Al-Mg-Sc-Zr alloy, Acta Mater. 50 (2002) 4165-4175.

DOI: 10.1016/s1359-6454(02)00258-6

[3] R.Z. Valiev, T.G. Langdon, Principles of equal-channel angular pressing as a processing tool for grain refinement, Prog. Mater. Sci. 51 (2006) 881–981.

DOI: 10.1016/j.pmatsci.2006.02.003

[4] Y. Estrin, A. Vinogradov, Extreme grain refinement by severe plastic deformation: a wealth of challenging science, Acta Mater. 61 (2013) 782–817.

DOI: 10.1016/j.actamat.2012.10.038

[5] R. Kaibyshev, E. Avtokratova, A. Apollonov, R. Davies, High strain rate superplasticity in an Al-Mg-Sc-Zr alloy subjected to simple thermomechanical processing, Scr. Mater. 54 (2006) 2119-2124.

DOI: 10.1016/j.scriptamat.2006.03.020

[6] F. Musin, R. Kaibyshev, Y. Motohashi, G. Itoh, High strain rate superplasticity in a commercial Al–Mg–Sc alloy, Scr. Mater. 50 (2004) 511-516.

DOI: 10.1016/j.scriptamat.2003.10.021

[7] R.S. Mishra, Z.Y. Ma, Friction Stir Welding and Processing, Mater. Sci. Eng. R 50 (2005) 1–78.

[8] S. Malopheyev, S. Mironov, V. Kulitskiy, R. Kaibyshev, Friction-stir welding of ultra-fine grained sheets of Al–Mg–Sc–Zr alloy, Mater. Sci. Eng. A 624 (2015) 132-139.

DOI: 10.1016/j.msea.2014.11.079

[9] F.C. Liu, Z.Y. Ma, Achieving exceptionally high superplasticity at high strain rates in a micrograined Al-Mg-Sc alloy produced by friction stir processing, Scr. Mater. 59 (2008) 882-885.

DOI: 10.1016/j.scriptamat.2008.06.035

[10] F.C. Liu, P. Xue, Z.Y. Ma, Microstructural evolution in recrystallized and unrecrystallized Al–Mg–Sc alloys during superplastic deformation, Mater. Sci. Eng. A 547 (2012) 55-63.

DOI: 10.1016/j.msea.2012.03.076

[11] O. A. Kaibyshev: Superplasticity of Alloy, Intermetallics and Ceramics, Springer-Verlag, Berlin, (1992).

[12] F.J. Humphreys, M. Hatherly, Recrystallization and related annealing phenomena. Oxford: Elsevier; (2005).