EFFECT OF RETAINED DEFORMATION ON THE AGE-PRECIPITATION BEHAVIOUR OF Mullite/Al-4.5Cu COMPOSITE AND ITS MONOLITHIC ALLOY

Short mullite fiber reinforced Al-4.5Cu composite and its monolithic alloy were produced by squeeze casting. The effect of the retained deformation made afterice-water quench with 0%,12.5%,25% or 34.4% and/or that of the fibers fabricated well with the matrix on the age-precipitation behaviour of the testing materials have been investigated by means of hardness measurement (HB),differential scanning calorimetry (DSC) and transmission electron microscope (TEM),respectively. The results indicate that the retained deformation considerably accelerates the ageing response of Al-4.5Cu alloy and the effect of precipitation acceleration is further promoted with increasing the deformation degree. Short mullite fibers also accelerate the ageing response of Al-4.5Cu alloy. Moreover,the age-precipitation progress of the testing composite is further accelerated when there exist both of the fiber and the deformation. The GP zone formation is, however,suppressed due to the introduction of retained deformation and/or short mullite fibers.