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Microhardness Studies on Al-8MG Alloys to Analyze the Deformation Behaviour

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Document pages: 12 pages

Abstract: Cylindrical samples of Al-8 wt pct Mg alloy were upset to 40 reduction followed by heat treatment at 2000C, 3500C and 4500C, respectively. Inhomogeneity in deformation due to friction at the platen interface and internal friction was studied by microhardness measurements in the roll direction. Results were quantified and analyzed by generating bar charts. Homogenized structures exhibit high and uniform hardness values compared to the as-cast ones. Retention of higher Mg concentrations in the solidsolution (making it supersaturated) with the cast-structures (chill-cast) is the reason for its greater in-homogeneity in deformation. Rejection of Mg from the supersaturated solidsolution followed by formation of Al3Mg2 is the reason for high hardness of homogenized structures. Upsetting followed by heat treatment not only enhances the uniformity in structure but also decreases the average hardness, with increasing heat treatment temperature. This could be attributed to the formation of new strain free grains and grain growth. A mathematical model has been developed and verified at other temperatures as well.

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