Metal-matrix composites are being used increasingly for the fabricatio
n of engineering components, yet the response of such materials to def
ormation is still poorly characterised. In an attempt to further the o
ptimisation of processing, the constitutive behaviour of the composite
s 6061/Al2O3/10p and 6061/Al2O3/20p has been investigated; for compari
son purposes, the unreinforced alloy was tested also. Compression test
ing was carried out at strain rates of between 0.01 and 10s(-1), at te
mperatures of between 300 and 550 degrees C. The resulting data were f
itted to the hyperbolic sine relationship and an internal stress relat
ionship. It was found that the constitutive behaviour of unreinforced
alloy could be characterised adequately by a single relationship over
the whole temperature range, whereas the behaviour of the composites w
as best described in two temperature ranges, above and below about 425
degrees C. The hyperbolic sine relationship was found to be the more
accurate in each case, however, for extrapolating to lower temperature
s, the internal stress relationship was found to be more reliable for
the composites. The change in constitutive behaviour at 425 degrees C
is related to the controlling mechanism in the two temperature regimes
: precipitation of beta' at low temperatures, and dynamic recrystallis
ation at high temperatures. This observation may need to be accounted
for in the commercial production of metal-matrix composites. (C) 1997
Elsevier Science S.A.