Abstract
During remelting of aluminum manganese-containing alloys, some industrial experience has indicated a tendency toward increased oxidation losses when compared to unalloyed Al. A goal of this work is to increase current knowledge of oxidation of Mn-containing aluminum. An oxidation study was performed on 99.99% Al, Al-1%Mn and Al-5%Mn materials in a muffle furnace in air. These oxidized materials were analyzed in the Scanning Electron Microscope using Energy Dispersive x-ray Spectroscopy (EDS) both for chemical composition and to analyze the structure of the oxide that was formed.
The main findings from the SEM analysis of the oxidized 99.99% Al, Al1%Mn and
Al5%Mn materials are:
1) The oxides formed on the Al1Mn and Al5Mn materials contained only minute amounts of Mn. However, small clusters of Mn metal were found among the Al2O3 particles on the surface of the Al1Mn and Al5Mn samples.
2) Dissolved Mn increased from the surface to the interior, and Mn-rich particles were present in the interior of the Al1Mn and Al5Mn samples.
3) The oxide layer thickness increases with Mn content, and the oxide film is more fragmented.
During remelting of aluminum alloys, industrial experience has shown a tendency toward increased oxidation losses with manganese-containing alloys. A goal of this work is to increase current knowledge of oxidation of Mn-containing aluminum alloys and relate this knowledge to reducing oxidation losses.
An oxidation study was performed on 99.99% Al, Al-1%Mn and Al-5%Mn materials in a thermogravimetric furnace with different atmospheres, and in a muffle furnace with air. The mass gain behaviour for these materials was studied and compared for different temperatures and surface preparations.
The results show that there was no Mn in the oxide on either the extruded or heated Al-1%Mn samples.
The mass gain at 800 and 1000°C for O2, CO2 and N2 atmospheres (with and without H2O) and for different surface treatments was less than 0.35%, and does not appear to explain increased oxidation losses experienced in industry when remelting Mn-containing alloys.
The main findings from the SEM analysis of the oxidized 99.99% Al, Al1%Mn and
Al5%Mn materials are:
1) The oxides formed on the Al1Mn and Al5Mn materials contained only minute amounts of Mn. However, small clusters of Mn metal were found among the Al2O3 particles on the surface of the Al1Mn and Al5Mn samples.
2) Dissolved Mn increased from the surface to the interior, and Mn-rich particles were present in the interior of the Al1Mn and Al5Mn samples.
3) The oxide layer thickness increases with Mn content, and the oxide film is more fragmented.
During remelting of aluminum alloys, industrial experience has shown a tendency toward increased oxidation losses with manganese-containing alloys. A goal of this work is to increase current knowledge of oxidation of Mn-containing aluminum alloys and relate this knowledge to reducing oxidation losses.
An oxidation study was performed on 99.99% Al, Al-1%Mn and Al-5%Mn materials in a thermogravimetric furnace with different atmospheres, and in a muffle furnace with air. The mass gain behaviour for these materials was studied and compared for different temperatures and surface preparations.
The results show that there was no Mn in the oxide on either the extruded or heated Al-1%Mn samples.
The mass gain at 800 and 1000°C for O2, CO2 and N2 atmospheres (with and without H2O) and for different surface treatments was less than 0.35%, and does not appear to explain increased oxidation losses experienced in industry when remelting Mn-containing alloys.