Room temperature strengthening mechanisms, high temperature deformation behavior and constitutive modeling in an Al-3.25Mg-0.37Zr-0.28Mn-0.19Y alloy

To improve the ambient strength and high temperature ductility, a novel Al-3.25Mg-0.37Zr0.28Mn-0.19Y (wt.%) alloy has been fabricated by multidirectional forging and warm rolling. Microstructures and mechanical properties were investigated by light microscope, X-ray diffraction apparatus, transmission electron microscope, and tensile tester. The ultimate tensile strength, yield strength, and elongation of 354.67 +/- 0.04, 254 +/- 3 MPa, and 18.47% were achieved in the processed alloy, respectively, at room temperature. The maximum super plasticity of 412.5% was demonstrated in this fine-grained (grain size of 8.80 +/- 1.06 mm) alloy at 793 K and 8.33 x 10(-4) s(-1). An ambient strengthening sequence was obtained: grain boundary strengthening > dislocation strengthening > Orowan strengthening > solid solution strengthening. The occurrence of Portevin-Le Chatelier effect or serrated flow in as-annealed alloy was confirmed by theoretical model estimation and experimental evidence. Micro structural evolution and flow stress curves confirmed that dynamic recovery and dynamic grain growth occurred at elevated temperatures; Sotoudeh-Bate curves were discovered at higher temperatures and lower strain rates. Solute Mg, dynamic grain growth, and flow localization were responsible for the formation of Sotoudeh-Bate curves. Modified Johnson-Cook constitutive equation considering dislocation variables and power-law constitutive equation were established. In this fine-grained alloy at 793 K and 8.33 x 10(-4)s(-1), the number of dislocations inside a grain was 6, the stress exponent was 2, the grain size exponent was 2, and the average activation energy for deformation was 140.10 kJ/mol. These pieces of evidence demonstrated that grain boundary sliding accommodated by intragranular dislocation controlled by lattice diffusion governs the rate-controlling process. (c) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

A novel Al-3.25Mg-0.37Zr0.28Mn-0.19Y (wt.%) alloy with improved ambient strength and high temperature ductility was fabricated using multidirectional forging and warm rolling. The alloy exhibited high ultimate tensile strength, yield strength, and elongation at room temperature, and demonstrated maximum superplasticity at elevated temperatures. The strengthening mechanisms in the alloy included grain boundary strengthening, dislocation strengthening, Orowan strengthening, and solid solution strengthening. The occurrence of Portevin-Le Chatelier effect or serrated flow was observed in the alloy, and constitutive equations were established to describe its behavior.