Influence of heat treatment on microstructure and electrochemical behaviors of Mg-Zn binary alloys prepared by gas-phase alloying technique

Mg-Zn binary alloys fabricated by the gas-phase alloying technique under vacuum condition were investigated in the state of initial state and after heat treatment for the microstructure and electrochemical behaviors. Different from the traditional Mg-Zn alloys preparation methods, alloys prepared by gas-phase alloying have a large number of intermetallic compounds, such as MgZn, Mg7Zn3 and MgZn2. After solution treatment, the boundary of the eutectic disappeared and the size of α-Mg increased from 100 μm to 150 μm. At the same time, the value of the resistance of charge transfer increased, which indicates that the resistance of the charge transfer and the corrosion resistance of the alloys increased. After artificial aging treatment, the distribution of α-Mg was more uniform and its size was reduced to about 50 μm, and there was new eutectic structure formed. The newly formed eutectic structure forms galvanic cells with the alloy matrix, which makes the corrosion resistance of the alloy weaken.