Pengaruh Preheat dan tekanan kompaksi terhadap sifat fisis-mekanis Metal Matrix Composites (MMCs) Aluminium-Fly Ash

AFRIZAL, Efi, Prof.Ir. Jamasri, Ph.D

2007 | Tesis | S2 Teknik Mesin (Mekanika Bahan)

Penelitian ini bertujuan untuk mengetahui pengaruh preheat dan tekanan kompaksi terhadap sifat fisis dan mekanis komposit aluminium-fly ash. Fly ash adalah residu hasil pembakaran batubara yang dapat dikelompokkan sebagai material keramik karena secara alami tersusun oleh beberapa senyawa oksida dengan kandungan tertinggi silika dan alumina. Sehingga fly ash dapat digunakan sebagai penguat untuk membentuk suatu Metal Matrix Composites (MMCs). Dalam penelitian ini fly ash dikalsinasi terlebih dahulu pada 800 oC selama 3 jam, kemudian dicampur dengan serbuk aluminium dengan komposisi fly ash dan aluminium (0-100), (5-95), (10-90) dan (15-85) dalam % berat. Masing-masing komposisi diaduk selama 5 jam serta dibagi dalam dua bagian. Bagian pertama mengalami preheat pada 150 oC selama 5 jam dalam tungku yang dialiri gas Argon dan bagian kedua tanpa preheat. Masing-masing bagian mengalami pre-compaction secara uniaksial dengan tekanan 50 MPa pada temperatur kamar, kemudian dikompaksi menggunakan metode Cold Isostatic Compaction (CIC) dengan tekanan 100 dan 120 MPa untuk membentuk green body. Green body yang dihasilkan ada dua yaitu silinder dan balok. Green body lalu disinter pada 575 oC selama 3 jam dalam furnace yang dialiri gas Argon. Spesimen hasil sinter diuji densitasnya dengan metode Archimides. Kekerasan diuji dengan Vickers dan kekuatan melalui four point bending. Struktur mikro diamati menggunakan mikroskop optik dan SEM. Hasil pengujian menunjukkan setelah dilakukan preheat terjadi peningkatan kekerasan Vickers 40,34%, sementara hasil lain tidak menunjukkan peningkatan yang signifikan seperti ketahanan aus 2,79% densitas 0,87%, sedangkan kekuatan bending tidak mengalami peningkatan. Komposit aluminium-fly ash yang memiliki kondisi optimum dihasilkan oleh kompaksi menggunakan tekanan 100 MPa, dengan fraksi penguat 10%. Pengamatan mikroskop optik dan SEM (Scanning Electron Microscopy) menunjukkan bahwa preheat dapat mengurangi timbulnya void, melalui pengujian EDS (Energy Dispersive Spectrometry) diketahui tidak terbentuk senyawa baru pada interface antara matrik dan penguat.

The purpose of this research is to find out the influence of preheat and the compaction pressure on the physical and mechanical properties of aluminum-fly ash composite. Fly ash is the residue of coal burning which can be considered as ceramic materials because naturally composed of several oxide substances with silica and alumina as the highest contens. Therefore fly ash can be used as the reinforcement of Metal Matrix Composites (MMCs). In this research, fly ash was calcined first at 800 oC for 3 hours, then was mixed with aluminum powder with compositions of fly ash and aluminum of (0-100), (5-95), (10-90) and (15-85) % weight. Each composition was mixed for 5 hours and it was then divided into two parts. The first part was preheated at 150 oC for 5 hours inside the furnace in argon gas atmosphere and the second one was not preheated. Each part was uniaxially pre-compaction with pressure of 50 MPa at room temperature, and then continued by compaction using Cold Isotatics Compaction (CIC) method with pressures of 100 and 120 MPa to produce green body. Two shapes of green body were produced, cylindrical and rectangular cross section bars. The green bodies were pressureless sintered at 575 oC for 3 hours in argon gas atmosphere. The density of sintered specimen was measured using Archimides method. The hardness and strength were examined using Vicker harness and four point bending test, respectively. The microstructures were observed using optical microscope and SEM. The result showed that after preheat was done there was an increasing of Vickers hardness 40,34%, while the other result did not show the significant increase such as wear resistance 2,79% the density 0,87 % while the bending strength did not experience increase. The aluminum-fly ash composite which has optimum condition was produced by the compaction using 100 MPa pressure, with 10 % weight reinforcement fraction. Optical microscope observation and SEM (Scanning Electron Microscopy) showed that preheat can reduce the appearance of void, through the EDS (Energy Dispersive Spectrometry) test it was known that there was no new substance on the interface between matrix and reinforcement.

Kata Kunci : Aluminium,Fly Ash,Sifat Fisis dan Mekanis MMCs, preheat, fly ash, MMCs, CIC, SEM, EDS, void, interface