COMPOSITE MATERIALS BASED ON ALUMINIUM ALLOY REINFORCED WITH Al2O3/Ti/C PREFORM

On the base of high temperature synthesis SHS porous ceramic prefoms for aluminum matrix composite reinforcing were produced. From mixture of Saffil alumina fibres, Ti powder and flaky graphite block samples were formed, dried and next placed in microwave chamber. Magnetron was supplied with constant power of 540 W to ignite and support reaction in flowing stream of CO2 gas. Fibres create initial skeleton build and preform strength, whereas Ti powder processed to hard titanium compounds. Temperature changes and velocity of synthesis front propagation were recorded. Temperature profiles were similar for all samples. The highest synthesis temperature of 1860 degrees C was detected for samples containing 10% Al2O3, 10% Ti and 5% of graphite, all the percentages v/v. Synthesis of some samples proceeded with second temperature increase as a result microwave radiation support. Microscopic observation showed sufficient structure homogeneity, though in some cases unprocessed Ti particles occurred. Chemical analyze EDS of reaction products revealed presence of oxides and complex Al and Ti compounds. Independently of graphite content these compounds formed folded strips around solid or empty volume. Depends on CO2 availability, reaction could be slowed down resulting in more compacted Ti compounds. Created as a result of combustion synthesis Ti compound after infiltration with liquid metal properly bounded with the matrix. It could be assumed that redox reaction proceeded and on surface of Ti compound alumina and Al-Ti compounds were created. The preforms with homogeneous structure were infiltrated with AlSi7Mg by squeeze casting method. Performed tests showed that reinforcement improved hardness HB and reduced thermal expansion.