DECOMPOSITION KINETICS OF MACHINING OIL AND OXIDATION OF A356.2 ALUMINUM-ALLOY IN ALUMINUM RECYCLING PROCESS

Citation
Sc. Lim et al., DECOMPOSITION KINETICS OF MACHINING OIL AND OXIDATION OF A356.2 ALUMINUM-ALLOY IN ALUMINUM RECYCLING PROCESS, Materials science and technology, 13(10), 1997, pp. 859-864
Citations number
20
Language
INGLESE
art.tipo
Article
ISSN journal
0267-0836
Volume
13
Issue
10
Year of publication
1997
Pages
859 - 864
Database
ISI
SICI code
0267-0836(1997)13:10<859:DKOMOA>2.0.ZU;2-I
Abstract
The recycling of scrap aluminium turnings or chips requires preprocess ing steps such as thermal degreasing, drying, and removal of other met al impurities on the surface of the scrap. The present study was perfo rmed using a thermogravimetric technique to understand the decompositi on kinetics of water-machining oil mixtures. The weight loss curves of a water-machining oil mixture showed two distinct inflections over th e temperature range studied (room temperature to 500 degrees C), with a residue of oil still remaining at 500 degrees C. Oxidation kinetics were studied and chemical analysis conducted of the oxide surface form ed in both dry air and moist air for A356.2 aluminium alloy (Al-7 wt-% Si-0.4 wt-%Mg) using a thermogravimetric technique and Auger electron spectroscopy/X-ray diffraction respectively. The results showed differ ent oxidation rate behaviour between oxidation in dry air and oxidatio n in moist air at temperatures above 525 degrees C. That is, oxidation in moist air showed a transition of parabolic to linear behaviour whi ch was not observed for oxidation in dry air. Auger electron spectrosc opy surface analysis and X-ray diffraction revealed that only aluminiu m oxide was formed at 300 degrees C while a duplex film of MgO/Al2O3 f ormed on the surface of the matrix at relatively high temperatures (55 0 degrees C). (C) 1997 The Institute of Materials.