Pengaruh tekanan kompaksi dan kandungan grafit terhadap sifat fisis dan mekanis pada komposit Al/Grafit

SETYANA, Lilik Dwi, Ir. M. Waziz Wildan, M.Sc.,Ph.D

2004 | Tesis | S2 Teknik Mesin

Komposit matrik logam aluminium dapat dibuat dengan cara metalurgi serbuk. Proses metalurgi serbuk umumnya menghasilkan porositas pada produknya, yang berpengaruh terhadap sifat fisis dan mekanisnya. Penelitian ini dilakukan untuk mengetahui seberapa besar pengaruh penambahan grafit dan tekanan kompaksi pada pembentukan komposit logam Al/grafit terhadap sifat fisis dan mekanisnya. Material yang digunakan dalam penelitian adalah serbuk paduan Al-Si sebagai matrik dan serbuk grafit sebagai penguat. Serbuk paduan Al-Si berukuran < 149 μm dengan bentuk partikel tidak beraturan, yang diperoleh dengan cara pengikiran. Serbuk grafit yang digunakan adalah fine powder, dengan variasi penambahan grafit 0; 2,5; 5; 7.5 dan 10% berat. Pembentukan spesimen dengan variasi tekanan kompaksi 300, 400, dan 500 MPa dan suhu sinter 550 oC selama 5 jam dalam lingkungan grafit. Pengujian sifat fisis meliputi pengukuran densitas relatif dan pengamatan struktur mikro dengan mikroskop optik dan SEM, analisa unsur fasa menggunakan EDX dan XRD. Pengujian sifat mekanis meliputi kekerasan Brinell, kekuatan bending, keausan dan pengujian radial crush strength pada spesimen bushing. Hasil penelitian menunjukkan bahwa dengan meningkatnya tekanan kompaksi meningkatkan densitas, kekerasan, kekuatan bending dan ketahanan aus dari komposit paduan Al-Si/grafit. Komposit Al-Si/5% berat grafit menghasilkan densitas relatif tertinggi yaitu 90%, kekerasan tertinggi 42,15 BHN dan laju keausan terendah 0,06 mm3/Nm. Spesimen tanpa penambahan grafit memiliki kekuatan bending dan radial crush strength tertinggi yaitu 42,02 MPa dan 10,5 MPa. Pada spesimen terjadi reaksi in-situ dengan terbentuknya Al4C3 selama proses sinter.

Aluminum metal matrix composites can be produced by powder metallurgy (P/M. Product of P/M generally contains porosity that influences to physical and mechanical properties. The aim of this research was carried out to influences graphite contains and compacting pressure on physical and mechanical properties Al/graphite composites. The materials used in this research were Al-Si alloy powder as the matrix and graphite powder as the reinforcement. The Al-Si alloy powder with irregular shape and particle size < 149 μm was produced by mechanical grinding method. Graphite powder particle is fine powder. The various content of graphite were 0, 2.5, 5, 7.5 and 10% weight. Each composition was compacted at various pressures of 300, 400, and 500 MPa to produced green bodies. The green bodies were then sintered at 550 oC for 5 hour in graphite environment. Density of specimens was measured using Archimedes method. Optical and SEM were used to observe the microstructures. EDX and XRD were used to analyze the elements or phase in the specimens. Mechanical properties of the specimens including Brinell hardness, modulus of rupture, wear resistance and radial crush strength of bushing components were also tested. The results of the research show that relative density, Brinell hardness, modulus of rupture and wear resistance of composites increase with increasing compacting pressure. The maximum value of relative density of 90%, Brinell hardness of 42.15 BHN and wear rate of 0.06 mm3/Nm were achieved on the composites containing 5% weight of graphite. The MOR and radial strength of the composites decrease with increasing graphite content, the maximum of MOR of 42.02 MPa and radial crush strength of 10.5 MPa were obtained on Al-Si alloy without graphite reinforcement. The graphite reacted with the Al matrix and form Al4C3 during sintering.

Kata Kunci : Komposit Al/Grafit,Tekanan Kompaksi,Sifat Jenis dan Mekanis, Al-Si/graphite composites, powder metallurgy, compacting pressure