Effect of Sr microalloying on microstructure and corrosion resistance of Al–4.6Mg alloy

Abstract

AbstractThe effect of Sr on the microstructure of Al–4.6Mg alloy is studied via optical microscopy, scanning electron microscopy‐energy‐dispersive analysis, electron backscattered diffraction, transmission electron microscopy, and the intergranular corrosion susceptibility is evaluated according to ASTM G67. The main precipitation phases of Al–4.6Mg alloy are β‐Al3Mg2 and Al6Mn, with a new square phase of Al3Mn also being formed. After the addition of Sr, the β‐Al3Mg2 phase of the alloy decreases, the morphology changes, and Al4Sr and τ‐Al38Mg58Sr4 phases are formed. Accordingly, the nanoscale precipitation phase τ‐Al38Mg58Sr4 is uniformly distributed inside the grains. Microstructure analysis shows that Sr promotes the dynamic recovery and dynamic recrystallization of the alloy, inhibits the growth of recrystallized grains, and reduces the alloy grain size from 14.294 to 10.273 μm. Additionally, the low‐angle grain boundaries increase, the high‐angle grain boundaries decrease, the texture of the rotated cube r‐{001}<110> improves, and the deformation texture decreases. The IGC susceptibility of the alloy is reduced with the addition of Sr, and the corrosion resistance in an electrolyte containing NaCl is enhanced.