Fig. 1. Schematic illustration for the experiments during (a) & (b) non-isothermal (continuous heating or cooling) and (c) isothermal processes; (d) the sketch of in situ electrical resistivity measurement.

Fig. 2. In situ electrical resistivity evolutions of AZ80 magnesium alloy during (a) non-isothermal and (b) isothermal processes.

Fig. 3. Micro-hardness evolutions and selected engineering stress-strain curves of AZ80 magnesium alloy during (a) & (c) non-isothermal and (b) & (d) isothermal processes.

Fig. 4. (a) DSC results and XRD patterns of AZ80 magnesium alloy during (b) non-isothermal (c) and (d) isothermal processes.

Fig. 5. SEM micrographs of selected quenched specimens during continuous heating process: (a) solid solution; (b) 200 °C of 2 °C/min; (c) and (g) 300 °C of 2 °C/min; (d) 450 °C of 2 °C/min; (e) 200 °C of 10 °C/min; (f) 300 °C of 10 °C/min and (h) EDS of the particle A in solid solution specimen (a).

Fig. 6. SEM micrographs of selected quenched specimens during continuous cooling process: (a) 350 °C; (b) 250 °C; (c) and (f) 150 °C; (d) and (e) room temperature.

Fig. 7. TEM micrographs of AZ80 Magnesium Alloy under different non-isothermal conditions: (a)-(c) 200 °C of 2 °C/min; (d)-(f) 300 °C of 2 °C/min; (g)-(j) cooling to 200 °C.

Fig. 8. SEM micrographs of the quenched samples at 150 °C: (a) 10 s with EDS in (d); (b) 10,000 s; (c) 50,000 s; (e) and (f) 100,000 s.

Fig. 9. SEM micrographs of the quenched samples at 200 °C: (a) and (b) 10 s; (c) and (d) 10,000 s; (e) and (f) 100,000 s.

Fig. 10. SEM micrographs of the quenched samples at 300 °C for (a) 5000 s & (b) 100,000 s with EDS results; and 350 °C for (c) 500 s & (d) 100,000 s.

Fig. 11. TEM micrographs of AZ80 magnesium alloy during isothermal processes : (a) & (b) 200 °C/10,000 s; (c) & (d) 200 °C/100,000 s; (e) & (f) 300 °C/100,000 s.

Fig. 12. Quantitative estimation of precipitation evolution in AZ80 magnesium alloy: (a) the mass fractions of β-Mg17Al12 precipitates calculated from Thermo-Calc software and electrical resistivity results at holding time of 105 s under various temperatures; (b) comparison of the volume fraction of precipitate from electrical resistivity and SEM micrographs during isothermal processes.

Fig. 13. Summaries of the precipitate characteristics based on in situ electrical resistivity results and microstructural observations under (a) non-isothermal processes and (b) isothermal processes.

Fig. 14. (a) Estimated time-temperature-precipitation (TTP) curves; (b) Relationship between micro-hardness and precipitation volume fraction.