Effect of hygrothermal environment on microstructure andmechanical properties of Zn-2Al filler metal

The aging degradation behavior of Zn-2Al filler metal in hot and humid environment was studied. High temperature and high humidity accelerating test was conducted to simulate the hygrothermal atmospheric corrosion condition. The influence of corroding time on the microstructure, mechanical properties and wettability of Zn-2Al filler metal was investigated. The experimental results displayed linear relationship between corroding depth and corroding time. Water vapor corroding primarily occurred at grain boundaries, and when corrosion reached a certain extent, corrosion cracks and corrosion holes formed. This intergranular corrosion was electrochemical corrosion with the intragranular zinc-rich η phase as the cathode but the aluminumrich α phase as the anode that dissolute at grain boundary. The tensile strength, plasticity and toughness of Zn-2Al filler metal decreased, and the wetting area of Zn-2Al filler metal on 1060 aluminum sheet also decreased sharply with the increase of corroding time.