Abstract
Semisolid slurries of 7075 aluminum matrix composite reinforced with nano-sized SiC particles were fabricated by ultrasonic assisted semisolid stirring (UASS) method. Rheoforming and thixoforming of typical cylindrical parts were investigated. The results show that high-quality semisolid slurries with spheroidal solid grain of 38 µm were fabricated by UASS. The nano-sized SiC particles were dispersed uniformly due to transient cavitation and acoustic streaming of ultrasonic wave and high and controllable viscosity of semisolid slurry. Typical cylindrical composite parts with good surface quality and complete filling were rheoformed and thixoformed successfully. Ultimate tensile strength (UTS) of the rheoformed and thixoformed composite parts are enhanced due to addition of nano-sized SiC particles. However, elongation decreased as compared to those of the matrix parts. Maximum UTS of 550 MPa was achieved in the thixoformed composite part with T6 treatment. Increase of dislocation density around the reinforcement particles leads to improvement of the strength and wear resistance of the composite.
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