MICROSTRUCTURAL CHANGES IN A MECHANICALLY ALLOYED AL-6.2ZN-2.5MG-1.7CU ALLOY-(7010) WITH AND WITHOUT PARTICULATE SIC REINFORCEMENT

Elemental powders of Al, Zn, Mg, and Cu (corresponding to the composit ion of 7010 aluminium alloy) were milled in a high-energy attritor wit h and without additions of SiC particulates. The microstructural chang es taking place in the milled powders (which eventually lead to mechan ical alloying) are found to be retarded by SiC additions. High-resolut ion techniques such as electron probe microanalysis (EPMA) and transmi ssion electron microscopy/energy-dispersive X-ray analysis (TEM/EDX) r evealed the presence of localized. solute-rich regions long after the diffraction line from these solutes had ceased to appear in the X-ray diffractograms, Zinc appears to be more difficult to be mechanically a lloyed into aluminum than either Cu or Mg in spite of its comparativel y larger diffusivity in aluminum.