# Al-Fe-Ni Metallic Glasses via Mechanical Alloying and Its Consolidation
## 3 Results and Discussion  
In the MA technique, the impact of the ball collision on the mixture of powder particles results in cold welding and fracturing phenomena. The change in particle powder size can be observed in the SEM micrographs (Figures 1 and 2). After milling for 5 h (Figure 1a), the powders milled at 250 rpm become agglomerated to form the irregular-feature microstructures because of the cold-welding phenomenon. Powder particles were formed reaching a size of 20-40 \(\upmu\)m. At the higher milling speed of 350 rpm, the size of the agglomerates was about 5-30 \(\upmu\)m (Figure 2a). At a higher milling time of 10 h, the morphology of agglomerates milled at 250 rpm changed from irregular microstructures to subspherical shapes (Figure 1b). At this stage, the strong collisions between balls or balls and vials during milling led to larger deformations of powders, and the fracture was dominant. For powders milled at 350 rpm, the grain sizes reduced only slightly. Continuing to a longer milling time from 20 h to 60 h, the as-milled powder tended to be finer for the 350 rpm, while at 250 rpm, the powder tended to fragment after 10 to 20 h of milling, and the powder had a tendency of agglomeration (due to cold-welding), returning to the grain size of powder milled for 40 h, and further refinement of milled powder up to 60 h (see Figure 3 and Table 2). The particle sizes continued to decrease and tended to be stable for both alloys at a milling time of 60 h. The fracturing of the particles must have occurred, resulting in reduced particle sizes at a longer milling time. After milling for 60 h, the morphology of both alloy powders tended to be a more spherical in shape (Figures 1e and 2e). \begin{table}
\begin{tabular}{c c c c} \hline
**Atom** & **Atomic Weight, g/mol** & **at.\%** & **wt.\%** \\ \hline Al & 26.98 & 82 & 68.52 \\ Fe & 55.84 & 14 & 24.21 \\ Ni & 58.69 & 4 & 7.27 \\ \hline \end{tabular}
\end{table} 
Table 1: The composition of the elemental powder mixture. Figure 1: SEM images of Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) alloy powders milled at 250 rpm for (**a**) 5 h, (**b**) 10 h, (**c**) 20 h, (**d**) 40 h and (**e**) 60 h.  
Figure 2: SEM images of Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) alloy powders milled at 350 rpm for (**a**) 5 h, (**b**) 10 h, (**c**) 20 h, (**d**) 40 h and (**e**) 60 h.  
Figure 3 displays a typical particle size distribution (a-b) of Al\({}_{\text{82}}\)Fe\({}_{\text{14}}\)Ni\({}_{\text{4}}\) powders after milling at 250 and 350 rpm for 60 h and the cumulative distribution of the alloy powders milled at (c) 250 rpm and (d) 350 rpm for different milling times. The median particle sizes (D\({}_{\text{50}}\)) of the Al\({}_{\text{82}}\)Fe\({}_{\text{14}}\)Ni\({}_{\text{4}}\) powders after milling at 250 and 350 rpm for 5 h are 26.6 \(\upmu\)m and 23.3 \(\upmu\)m, respectively (Table 2). At the same milling time, the particle sizes of powders milled at 250 rpm were smaller than those of powders milled at 350 rpm. This is in agreement with the particle size in SEM (Figures 1a and 2a). When the milling time was prolonged from 10 to 20 h, the powder particle sizes drastically decreased. The median particle diameters (D\({}_{\text{50}}\)) of powders milled for 20 h at 250 and 350 rpm were about 11.8 and 22.8 \(\upmu\)m, respectively. After milling for 60 h, the powders tended to become more uniformed. The median particle diameter (D\({}_{\text{50}}\)) of powder particles milled at 250 and 350 rpm reduced to 11.1 and 9.5 \(\upmu\)m, respectively. This is because of the dominance of fracturing over the cold