Developing Carbon Particle Reinforced Alnmininm Composite byPowder Metallurgy

Pure aluminium powder with average particle size of 25 um was pressed at 580
MPa reaching a green density of 97.5% theoretical density to form a circular disk.
Sintering was carried out under argon gas atmosphere at 620°C for 3 hours. The
effect of sintering conditions (temperature, time, and atmosphere) was evaluated by
cutting the disk and hardness was measured. SEM and EDX were used to study
microstructural characterisation and particle content of the sintered materials. To
improve the properties ofpure aluminium disk, certain modification was made in the
procedures. At this time, the aluminium powder was compacted with 464 MPa
pressure to produce green density of92% theoretical density. Sintering was done
under nitrogen gas atmosphere for 15 minutes at temperature of 630°C. After
sintering, the properties ofsintered material were evaluated to compare with the first
disk. The major different between these two samples isthe compaction and sintering
properties used to develop the end products. During cutting process, the second
sample sintered in nitrogen showed higher hardness than the first sample. For
composite compaction, three samples were prepared with 3%, 4% and 7% ofcarbon
in term of volume percent to be added to aluminium powder with addition ofwax as
binder. By using 255 MPa compaction pressure, sample with 3% ofcarbon produced
high strength green compact while there are some loose powder on the surface of
another two samples. Sintering for the three samples was carried out under nitrogen
atmosphere within two stages. Burn offprocess toremove wax at 350°C for one hour
and sintering at maximum temperature of 620°C for one hour. The properties of
composite material was evaluated using hardness test mid to be compared to
properties of pure aluminium compact. The hardness of composite material is less
than pure aluminium compact and it is suitable to use as self-lubricating material due
to the present of carbon.