Investigation Of The Processing, Microstructure And Mechanical Properties Of Bulk5083Nanostructured Grained Aluminum By Rapid Solidfication And Powder Metalurgy

Bulk nanocrystalline(NC)/ultrafine grained(UFG)5083aluminum alloys wassuccessfully synthesized via rapid solidification and powder metallurgy method. The rapidsolidification method was choosed the melting spinning then get ribbons. Ribbons brokeninto micro-scale powder with nano-scale grains. Aluminum powders was consolidated intobulk materials by high pressure sintering. Microstructure information such as grain size，alloying elements solid-solubility，dislocation density for ribbons，powders，bulk materialswere characterized using optical microscopy (OM), X-ray diffraction (XRD), scanningelectron microscopy (SEM) and transmission electron microscopy (TEM). Mechanicalproperties of NC aluminum bulk materials, such as microhardness and tensile properties,were measured and studied in terms of microstructure and fractographs.The grian size of ribbons were characterized with anodization and observed underpolarized light in an OM. It is shown that the microstructures was different in thethickness direction and the thickness of about30-100μm with the change of cooling rate.The wheel side with mean7μm equixed grains while the air side gained20-30μmelongated morphology grains. The dislocation density and alloying elements dissoluting inAl matrix was characterized by TEM and XRD. The result revealed that alloying elementsalmost completely dissoluted and grain interiors with1014m-2high dislocation density. Theaverage microhardness increased from113HV to123HV for the melt spun ribbons by20minutes heat treatment in200℃.The scale of powders for ball-milling were characterized by SEM shown that differentPCA content ratio received different particle size and grain size characterized by TEM andXRD. It is shown that the particle size was4-10μm with average grain size22nm whilethe particle size was50-100μm with average grain size32nm. The aluminum bulkmaterials grain size were characterized by TEM shown the the grain size almost didn’tgrew up at sintering temperature480℃（T/Tm=0.82）and grew up to100-200nm at560℃(T/Tm=0.99). The oxide film of particle was partially broken into oxide plates whilemost of oxide film still continuous distribution didn’t broken. The density of bulkmaterials was2.6413g/cm3achieving the99.8%theoretical density. The microhardness is decreased from226HV to170HV in the grain size growing up process. Upon tensiletesting, brittle fracture occurred under low stress, showing poor ductility was caused bybreaking condition of the oxide film in the grain boundary. The tensile testing confirm thatthe oxide film broken area show the dimple morphology and continuous film show alongthe particle boundaries fractograph morphology.