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. (C) 2009 Elsevier Inc. All rights reserved.