Peningkatan Sifat Mekanik Paduan Aluminium A356.2 dengan Penambahan Manganese (Mn) dan Perlakuan Panas T6

Abstract

Aluminum Alloy A356.2 is one of aluminum alloys that is suitable to be used as a car wheel - rim material. This is because it has some benefits such as lightweight material, corrosion resistance material, interesting color but its mechanical properties do not meet criteria of JIS H 5202. For that reason, to meet the standard its mechanical properties need to be improved. Mechanical properties of this alloy can be improved using many ways; one of these is by changing its chemical composition. In this research, Mn element is added to alloy A356.2 containing Mn 0.05%w originally. Mn addition to the alloy is commenced from the amount of 0.2%w, 0.4; 0.6; 0.8; 1.0; 1.2; 1.4 and finally 1.6%w. After this, some tests are conducted to these new alloys including tensile test, hardness test, impact test and micro - structural test. Test results show that the change of material mechanical properties occurs due to Mn addition and heat treatment T6 to these alloys. The optimum mechanical properties are obtained with the addition of 1.2%w Mn to the alloy. In this condition, the alloy has Ultimate Tensile Stength of 31.58 kg/mm2, elongation of 7.54%, hardness test of 90.74 HVN and impact test of 5.88 J/cm2 and these results fulfill JIS H 5202 standard. Abstract in Bahasa Indonesia : Paduan Aluminium A356.2 merupakan salah satu paduan aluminium yang cocok dipakai untuk material velg-racing mobil. Karena paduan ini mempunyai beberapa kelebihan seperti; ringan, tahan korosi dan warnanya menarik, tetapi sifat mekaniknya belum memenuhi standar JIS H 5202. Oleh karena itu maka sifat mekaniknya perlu ditingkatkan. Sifat mekanik paduan dapat ditingkatkan dengan beberapa cara, salah satunya adalah dengan mengubah komposisi kimia dan perlakuan panas. Pada penelitian ini dilakukan penambahan unsur Mn ke dalam paduan A356.2 sehingga kandungan Mn yang semula 0.05%w dinaikkan menjadi; 0.2, 0.4; 0.6; 0.8; 1.0; 1.2; 1.4 dan 1.6%w. Setelah itu diberi perlakuan panas T6, kemudian dilakukan uji kekuatan tarik, kekerasan, impak dan pengamatan struktur mikro. Hasil pengujian menunjukkan bahwa sifat mekanik paduan, naik akibat adanya penambahan Mn dan perlakuan panas T6. Sifat mekanik optimum diperoleh ketika kandungan Mn sebesar 1,2%w. Pada kondisi ini mempunyai nilai Ultimate Tensile Stength 31.58 kg/mm2, elongation 7.54%, kekerasan 90.74 HVN dan kekuatan impak 5.88 J/cm2, dan telah memenuhi standar JIS H 5202. Kata kunci: Paduan Aluminium, ultimate tensile strength, kekerasan, kekuatan impak