# Al-Fe-Ni Metallic Glasses via Mechanical Alloying and Its Consolidation
## 4 Conclusions  
This work investigated the influence of high-energy mechanical milling on the microstructures and magnetic properties of Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) amorphous alloys prepared by mechanical alloying. During the milling process, Al, Ni and Fe atoms in Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) alloy powder can interact with each other to form a supersaturated solid solution Fe(Al,Ni) before the formation of a completely amorphous structure. The amorphization of alloy powders milled at 350 rpm takes place earlier than that of powders milled at 250 rpm. After 60 h of milling, both alloys have a fully amorphous structure.  
The saturation magnetization of powders milled at both 250 and 350 rpm is decreased with an increase in the milling time, which supports the results of the phase analysis. The coercivity force values also decrease after 5 h of milling due to the reduction of the  
\begin{table}
\begin{tabular}{c c c} \hline
**Alloys** & **Compression Strength (MPa)** & **Relative Density (\%)** \\ \hline Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) (450 \({}^{\circ}\)C) & 600 & 88.4\% \\ Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) (500 \({}^{\circ}\)C) & 650 & 92.6\% \\ Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) (600 \({}^{\circ}\)C) & 710 & 97.1\% \\ \hline \end{tabular}
\end{table}
Table 4: Relative densities and compression strengths of the sintered samples.  
Figure 10: XRD patterns of amorphous Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) samples (**a**) after milling for 60 h, (**b**) sintered at 450, (**c**) 500 and (**d**) 600 \({}^{\circ}\)C.  
crystalline size of the alloy and the formation of the amorphous phase. This reveals that the samples exhibit a paramagnetic behavior.  
The crystallization of two alloys corresponds to the devitrification of the amorphous phase mainly into cubic fcc-Al beyond the primary crystallization peak and followed by transformation into intermetallic phases. The crystallization onset temperature of amorphous powders milled at 250 rpm is 341 \({}^{\circ}\)C, which is lower than that of powders milled at 350 rpm (377 \({}^{\circ}\)C). This indicates that the amorphous powders milled at higher speeds possess higher thermal stability. Milling speed possesses a significant influencing performance on the ball-milling process in terms of the energy impact, microstructural evolution, thermal stability and magnetic properties of as-milled powder alloys. Following the sintering of amorphous alloy powders milled at 350 rpm at 600 \({}^{\circ}\)C under a pressure of 300 MPa, a highest density of 97.4% and a compressive strength value of 710 MPa was obtained. The morphology of the failure surface of the bulk amorphous Al\({}_{82}\)Fe\({}_{14}\)Ni\({}_{4}\) alloy shows the transparticle fracture mechanism, indicating the efficiency of the sintering condition.  
Conceptualization, N.H.V. and N.T.H.O.; methodology and investigation, D.N.B. and N.H.V.; software, D.N.B.; validation, N.H.V. and N.T.H.O.; writing--original draft preparation, D.N.B.; writing--review and editing, N.H.V. and N.T.H.O.; visualization, N.H.V. and D.N.B.; supervision, N.H.V.; project administration, N.T.H.O.; funding acquisition, N.T.H.O. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the Ministry of Industry and Trade of the Socialist Republic of Vietnam under grant number: DT.BO.107/21 (Contract number: 107.2021.DT.BO.HBKHCN).  
Not applicable.  
The authors declared no potential conflict of interest with respect to the research, authorship, and publication of this article.