# Analysis of Nucleation and Glass Formation by Chip Calorimetry
## 3 Results and Discussions
### Stable La-Based MG  
For the stable La-based MG system, the thermal signals for the glass transition and primary crystallization are strong [26]. To verify if the above new method to confirm the delay time for primary crystallization is effective for the La-based MG, one typical composition of La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) was selected and the target temperature was set at 270 \({}^{\circ}\)C. Then, a series of Flash DSC heat flow curves corresponding to different annealing times ranging from 1 s to 50 s with the heating rate of 500 K/s were measured, as shown in Figure 4a. From Figure 4a, the heat flow curves with different annealing times for La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) MG exhibit the obvious signals of the glass transition and primary crystallization. The onset values of the glass transition obviously shift to the higher temperature range with the increase of the annealing times, which is consistent with the structural relaxation effects in MGs [24; 25]. Similar to the analyses process for the delay time confirmation method in part (1) for Al-based MG, the onset value of the glass transition \(T_{g}\) with the annealing time \(t_{a}\) can be plotted as shown in Figure 4b. From Figure 4b, it is apparent that with the increase of \(t_{a}\) at 270 \({}^{\circ}\)C, a break point time appears at 22.5 s. Before and after 22.5 s, the evolution paths of \(T_{g}\) with \(t_{a}\) can be roughly fitted by two lines with different slopes corresponding to two different governing mechanisms of the structural relaxation and the composition change induced by the crystallization. In comparison, the isothermal method (method II in Figure 2b) was also applied to measure the delay time for La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) MG sample at 270 \({}^{\circ}\)C. The detailed temperature program can be seen in Figure 2b. As shown in Figure 4c, at 270 \({}^{\circ}\)C, when the annealing time increases into about 24 s, the exothermic peak corresponding to the primary crystallization appears. The time of 24 s is the delay time at 270 \({}^{\circ}\)C, which is very close to the experimental data of 22.5 s by the Flash DSC method. To confirm if the delay time of the experimental breaking time of glass transition temperature with annealing time in Figure 4b corresponds to the onset time for primary crystallization, two annealing time points were selected before and after the break time, \(t_{1}\) (20 s) and \(t_{2}\) (25 s). Then, for these two annealed samples obtained by Flash DSC, XRD tests were conducted to characterize the sample state. The corresponding XRD patterns corresponding to the annealing times of \(t_{1}\) and \(t_{2}\) are shown in Figure 4d. It is apparent that at 270 \({}^{\circ}\)C, the sample with the annealing time of 20 s before the break point is still amorphous without any crystals; in contrast, for the samples with the annealing time of 25 s after the break point time, one sharp crystallization peak was observed, which indicates that the annealed sample is crystallized. Thus, the above results show that the break point time of 22.5 s is actually the delay time at 270 \({}^{\circ}\)C for the stable La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) MG.  
(3) Stable Mg-Based MG  
Similar to the stable La-based MG, the Mg-based MG with a composition of Mg\({}_{65}\)Cu\({}_{25}\)Gd\({}_{10}\) is also one of the typical stable MG systems [27]. As shown in Figure 5a, a series of Flash DSC heat flow curves were obtained corresponding to different annealing times ranging from 5 s to 60 s at 200 \({}^{\circ}\)C with the heating rate of 500 K/s. The heat flow curves with different annealing times for Mg\({}_{65}\)Cu\({}_{25}\)Gd\({}_{10}\) MG exhibit the clear signals of the glass transition and primary crystallization, which are consistent with the thermal behaviors for La-based MG in part (2). What is more, the \(T_{g}\) shifts to the higher temperature with the increase of the annealing time \(t_{a}\).