Effect of Extensive Isothermal Rolling on Microstructure and Mechanical Properties of an Al-Mg-Sc Alloy

Abstract

The evolution of microstructure and mechanical properties of an Al-5.4Mg-0.4Mn-0.2Sc-0.09Zr alloy subjected to rolling at 300oC was studied. It was shown that the rolling of the alloy leads to strong anisotropy in mechanical properties. The formation of the lamellar structure occurs at a total reduction of 60% due to alignment of initial boundaries along rolling direction (RD), and appearance of geometrically necessary boundaries (GNB) aligned with {111} planes. This process is accompanied by a strong increase in the lattice dislocation density by a factor of 50. Further rolling induces the formation of subgrains within lamellar structure that diminishes the anisotropy. The GNBs have low-angle misorientations, initially. After a reduction of 80%, minor part of GNBs acquires high-angle misorientation. The formation of well-defined subgrains within lamellas leads to a decrease in the lattice dislocation density by a factor of about 10; the yield stress (YS) decrease is -25% along the RD. At the same time the YS in the transverse direction tends to increase with increasing reduction from 60 to 80%. The effect of the deformation structure on the mechanical properties and their anisotropy is discussed.