ENHANCEMENT OF MICROSTRUCTURE AND THERMAL EXPANSION COEFFICIENT OF AL/NI-SIC COMPOSITE PREPARED BY POWDER METALLURGY TECHNIQUE

Al/Ni-SiC composite was prepared via powder metallurgy technique, in which SiC particles were mixed with 10 wt % nickel powder for 24 hrs, then mixed by three percents 5, 10 and 15 wt.% with Al powder in a ball mill for 5 hrs. Three types of sintering techniques were used to prepare the composite. Uniaxial cold compacted samples were sintered in a vacuum furnace at 600oC for 1 hr. The second group was the vacuum sintered samples which were post-processed by hot isostatic press (HIP) at 600oC for 1hr under 190 MPa pressure. The third one was the hot pressed samples that were consolidated at 550oC under the uniaxial pressure of 840 MPa. The results showed that the hot compacted samples have the highest densification values (97-100%), followed by the HIP samples (94-98%), then the vacuum sintered ones (91-97%). The XRD analysis indicated the presence of peaks correspond to Al and Ni, also Al3Ni intermetallic and Al4Si2C5 phases which indicated that all SiC particles were consumed with Al particles to form Al4Si2C5. Hardness results revealed that hot compacted samples have the highest hardness values. Also the CTE results referred the decreasing of its value by increasing Ni/SiC percent.