Microstructure and mechanical properties of wrought aluminium alloy prepared by recycling of aluminium matrix composites reinforced with Inconel 601 fibres

The microstructure and mechanical properties of Al-2.2Cu-1.7Mg-1.1Ni-1.1Fe- 0.9Si-0.3Zn-0.2Cr-0.2Mn-0.2Ti (wt.%) alloy prepared by recycling of composi te scrap containing Inconel 601 fibres in aluminium matrix were investigate d. The structure of recycled alloy consisted of alpha-Al dendrites and a mu ltiphase interdendritic region. Transmission electron microscopy and energy dispersive X-ray spectroscopy showed that the interdendritic region contai ned coarse Al9Fe(Ni, Si), Al7Cu4Ni, Al4CuMg5Si4, (Cu, Al)(2)Mg and Mg2Si in termetallic phases distributed in the alpha-Al matrix. Heat treatments resu lted in additional hardening of the alloy through the precipitation and gro wth of fine theta-Al2Cu, S-Al2CuMg and beta-Mg2Si intermetallic particles i n the alpha-Al matrix. Peak microhardness, hardness and yield strength valu es were reached after 20, 12 and 8 h ageing at 180, 190 and 200 degrees C, respectively. During the early stages of plastic deformation both intermeta llic particles in the interdendritic region and small precipitates in the a lpha-A matrix contributed to the high strain hardening of the alloy. The br eakage of coarse intermetallic particles resulted in a considerable reducti on of the strain hardening exponent and quasi-steady strain hardening rate. The alloy failed by the coalescence of cavities formed within broken inter metallic particles and small voids formed around the precipitates. (C) 1999 Elsevier Science S.A. All rights reserved.