Unravelling the precipitation evolutions of AZ80 magnesium alloy during non-isothermal and isothermal processes

The precipitation evolutions of Mg-Al-Zn alloys play essential roles in their mechanical properties, corrosion performance, formability, plastic deformation mechanisms and texture development. In the present work, the precipitation evolutions of AZ80 magnesium alloy during both non-isothermal and isothermal processes were unraveled by utilizing in situ electrical resistivity monitoring, hardness testing, differential scanning calorimetry and microstructural characterization. The results showed that discontinuous precipitation（DP） and continuous precipitation（CP） occurred competitively during non-isothermal and isothermal processes. The precipitation of dominant β-Mg17 Al12 phase during non-isothermal processes was highly dependent on the thermal history. During isothermal processes, the precipitation behavior of AZ80 magnesium alloy could be considered as the functions of holding temperature and time. At lower temperatures, massive DP and CP were gradually formed to equally strengthen the alloy. At higher temperatures, the Ostwald coarsening was characterized in the later stages and indicated to slightly soften the alloy. Isothermal time-temperature-precipitation curves and quantitative precipitate evolution were estimated to unravel precipitation characteristics and their strengthening functions.