An improvement in casting of aluminium alloy graphite particulate comp
osite synthesized by stir casting is discussed. About 15 wt.% graphite
particles were dispersed in Al-Si-Mg (LM 25) alloy by the rheocasting
technique. The composite ingots were used as a master alloy and dilut
ed further with LM 25 alloy to obtain a 5 wt.% dispersion of graphite
in the matrix. The composite ingots thus processed were subsequently r
emelted and pressure die cast into plates. Macroscopic and microscopic
examination of the plates revealed fewer defects and a fine distribut
ion of particles. The ultimate tensile strength evaluated in this comp
osite was superior (132-136 MPa) to that of gravity die cast (85-95 MP
a) composites. The fracture toughness of the composites was in the ran
ge 8-10 MPa m1/2.