At the UFPE (Unversidade Federal de Pernambuco), with the collaboration of AIMEN researchers, studies based on cryomilling are being developed to obtain nanostructured light alloys and nanocomposites under the FUNCTIONAL project. Different matrices, reinforcements and milling parameters are being studied.
Cryomilling is a mechanical attrition technique in which powders are milled in a slurry formed with milling balls and a cryogenic liquid. As a process relying on severe plastic deformation, the formation of nanostructures within the powder particles can be compared to other ball milling methods, as well as to microstructural refinement of bulk materials, attained via equal channel angular pressing (ECAP), friction stir processing (FSP), accumulative roll bonding (ARB) and others. As a powder metallurgy technique, it requires a consolidation step, and changes in microstructure and properties during consolidation can be expected. The strength of the material can be enhanced by refining the microstructure regarding to grain size.
Advantages of Cryomilling regarding to the traditional ball milling are:
· Suppression of annihilation of dislocations resulting in a larger dislocation density due to the low temperature. Therefore, milling time is reduced
· More efficient milling process as a result of the restriction of the agglomeration and cold welding even without using PCA (Process Control Agent).
· Nitrogen environment reduces oxidation of the powders
Figure shows the cryogenic mill used
at the UFPE