Influence of Zn Content on the Microstructure and Properties of As-annealed Al-Mn-Si Alloys

The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed Al-Mn-Si alloy was investigated through TEM observations, anodization metallography, tensile tests and Tafel polarization analysis. High density precipitates were found in the Zn-containing alloys and the alloy with 1.5 % Zn had the most uniform precipitation. The Zn element could restrain recrystallization of the alloy. Tensile test results indicated that Zn has a great effect on tensile strength of Al-Mn-Si alloy. The alloy with 1.8 % Zn addition had the highest ultimate tensile strength. The electrochemical testing results indicated that Zn element had great impact on the corrosion potential of the as-annealed alloys tested in 0.5% NaCl solutions. Alloying with Zn element could make the corrosion potential shift to negative direction but increase the resistance to pitting corrosion.