High strain rate superplasticity in friction stir processed ultrafine grained Mg–Al–Zn alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 562; pp. 69 - 76
• Main Authors: Mohan, A., Yuan, W., Mishra, R.S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01-02-2013; Elsevier
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Contact of materials. Friction. Wear; Deformation and plasticity (including yield, ductility, and superplasticity); Elasticity. Plasticity; Exact sciences and technology; Forming; Grain growth; Grain refinement; Magnesium alloys; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Physics; Production techniques; Rolling; Superplasticity; Superplasticity; Grain growth; Magnesium alloys; Grain refinement; Grain size; Temperature dependence; Material processing; Rolling; Mechanical properties; Precipitate; Tension test; High pressure; Friction stir; High speed; Magnesium alloy; Fine grain structure; Kinetics; Microstructure; Elongation (mechanics); Tribology; Strain rate
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.11.026

Friction stir processing of a rolled AZ31 alloy and a high pressure die cast AZ91 alloy produced ultrafine grained materials with average grain size of 0.8μm and 0.5μm, respectively. Tensile testing was done in the temperature range of 210–360°C and strain rate range of 1×10−4–3×10−2s−1. Higher amounts of β-precipitates in AZ91 thermally stabilized the microstructure up to 330°C. Friction processed ultrafine grain AZ91 exhibited high strain rate superplasticity at all tested temperatures. The best elongation of 1251% was achieved at a strain rate of 1×10−2s−1 and temperature of 330°C. The kinetic analysis of the superplastic data revealed a large variation in the kinetic parameter due to difficulty in using proper grain size values because of concurrent grain growth.