Effect of Sc and Zr Addition on the Microstructure and Properties of Al-Mg-Mn Alloy

Abstract

The microstructure and mechanical and corrosion properties of Al-Mg-Mn alloys were studied after adding Sc and Zr as microalloying elements. The results show that the presence of Sc and Zr can refine the microstructure of the alloy, and the size of as-cast alloy grains is reduced from 172 μm to 41 μm by adding 0.4% Sc and reduced to 26 μm by adding 0.2% Sc and 0.2% Zr. According to scanning electron microscopy, the abundant second phase of Al3Sc and Al3(Sc, Zr) has the same shape in the hot-rolled aluminum alloy sheet as in the as-cast state, indicating that the second phase particles are linearly distributed and do not undergo plastic deformation during the plastic deformation process but only rotate along the rolling direction. After annealing at 200 °C, the yield strength of the pristine aluminum alloy sheet is reduced to 186 MPa. After annealing at 250 °C, the yield strength of the Zr-containing aluminum alloy sheet is reduced to 195 MPa. When Sc element or both Sc and Zr elements are added, the yield strength of the obtained aluminum alloy sheet remains above 250 MPa, even when the annealing temperature rises to 300 °C. Based on electrochemical tests, an alloy plate containing 0.2% Sc and 0.2% Zr and annealed at 200 °C has the best corrosion resistance, followed by the alloy plate containing only Sc, while the alloy plate without microalloying elements has the worst corrosion resistance.

Keywords: Al-Mg-Mn alloy, microstructure, annealing, tensile strength, Corrosion properties