The Microstructure And Property Of Al-Fe Based Alloy Prepared By The Semi-solid Formation Technology

Iron-rich phase in Al-Fe alloy has a shape of thick fragility needle-like or needle-plate, which will cause the reduction of the alloy mechanical property. This paper has studied the technique to improve the phase shape for increasing the mechanical property of Al-Fe alloy. The study work has been center on the design of chemical composition and the affection of alloying elements and preparing technology on the microstructure and properties of Al-5.5Fe based alloy. Al-5.5Fe-4Cu-2Zn-0.4Mg-0.5Mn alloy becomes the alloy final chemical composition. The electromagnetic stirring, nearby liquids, reheat and semi-solid extruding formation technologies on the microstructure and properties of the alloy has been studied systematical. At last, the heat stability of the alloy has been tested.The experimental results indicate that the second phase size of Al-5.5Fe based alloy is obvious refined by addition different quantity Mn, Cr elements; the second phase is more refinement and uniform distribution by the electromagnetic stirring processing. The maximum tensile strength of the alloy at cast condition is 161.6MPa. When the electromagnetic stirring voltage is 150V, the length of needle-like phase decreases 30% comparing with as cast condition; the nearby liquids processing also can effectively refine the second phase size. When suitable processing parameters is casting temperature 680℃and soaking time 30min, the second phase is obvious refined, and the partial second phase shape has been changed into graininess. The length of Al₃Fe phase is only 20% comparing with as electromagnetic stirring processing.Semi-solid extruding formation technology could further refine the second phase of Al-5Fe based alloy. The higher the extrusion ratio is, the more obvious the effectiveness of refining and breaking, and the more uniform of distributing of Al₃Fe phase. When the extruding ingot is processed by electromagnetic stirring, the length of the second phase is about 50μm, decreased 75% comparing with as cast condition. When the extruding ingot is processed by nearby liquids, the length of the second phase is about 20μm, decreased 90% comparing with as cast condition. Semi-solid Formation technology can improve the mechanical property of Al-5.5Fe-4Cu- 2Zn-0.4Mg-0.5Mn alloy, and with the increasing of extrusion ratio, the tensile strength and elongation percentage is improved. The maximum tensile strength is 329.5MPa, increased 104% comparing with as cast condition, the maximum elongation percentage could reach 2.2%.Heat stability test results shows that the microstructure of Al-5.5Fe-4Cu-2Zn-0.4Mg-0.5Mn alloy has a very ideal heat stability at 200℃, and its HB is about 86.1. The HB of the alloy has been decreased 12% and 11.6% after soaking 150h and 200h continuously.