Characterization of nanocrystalline Al-based alloy produced by mechanical milling followed by cold-pressing consolidation

In the present study high energy mechanical milling followed by high-pressing consolidation has been used to obtain bulk nanocrystalline aluminum based alloy. Fully dense disks with homogenous microstructure were obtained. X-ray analysis indicates that high strain imposed by mechanical milling and severe plastic deformation (SPD) processing causes microstructure showing a mixture of a significant lower value of the crystallite size (around 60 nm) and the creation of a large number of linear defects which induces microstrains (around 0.7%). In addition, the elevated value of hardness which was obtained for the consolidated disks and the favorable comparison with the value measured for the same as-received alloy confirm the potential of the SPD technique when it is collected with high energy mechanical milling for producing higher performance materials. On the basis of calorimetric measurements, as a function of consolidation stresses, we can say that the thermal behaviour was characterized by a significant heat release and grain growth during the heating cycle. Moreover, the noticed broad endothermic peak can be attributed to some precipitants containing magnesium.