Study On Microstructure And Properties Of 5052 Aluminum Alloy By Trace Element And Extrusion Treatment

The effect of the trace elements on the microstructure and properties of 5052 aluminum alloy modified by Er, Sr and Cu were studied in the paper. The billets fabricated by die casting were extruded at the temperature of 390, 420 and 450℃ after homogenizing treatment. The microstructure and mechanical properties of the 5052 aluminum alloys were analyzed by means of optical metallographic microscope, scanning electron microscope, energy disperse spectroscopy, x-ray diffractometer, differential scanning calorimeter, as well as room temperature tensile test and hardness test.The results show that there is no composition difference in the Al3 Fe phase of the alloys modified by Er and Sr elements compared with the original alloys, but morphology of Al3 Fe phase significantly is improved. The transformation occurs from needle sheet-like Al3 Fe phase respectively to the fibrous and flower-like in the 5052 alloys modified by Er and Sr elements. The microstructure transformation of the 5052 alloy modified by Cu is very obvious, generating Al7Cu2 Fe and Al6(Fe Cu)mixed phases and ɑ(Al), Al2 Cu and Al2 Cu Mg ternary eutectic phases. After homogenizing treatment,the microstructure of the 5052 alloy and 5052 alloys modified by Er and Sr has almost no change,but Al3 Fe phases are broken and refined. In the alloy modified by Cu, the ternary eutectic phases are almost completely dissolved, and there can be observed more binary eutectic ɑ(Al)+Si phases. In addition, the transformation from Al6(Fe,Cu) to Al7Cu2 Fe phase occurs during the homogenization treatment. The strength and hardness of the alloys are improved after joining trace elements.After hot extrusion, the obvious microstructure change that different forms of Al3 Fe phases are cracked occurs, presenting the streamline distribution along the extrusion direction. The particles arrangement of edge is much more dense and uniform than the center position, and the alloy microstructure modified by Er, Sr and Cu is even more dense and uniform than the original alloy.After hot extrusion by 390, 420 and 450℃, the microstructure is mainly composed of the recrystallization grains and the deformation organization in the alloy modified by Er element.However, the rest alloys are all made up of tiny recrystallization grains. At the same time, all the alloy grains size from edge to center position constantly decrease. With the increasing of the extrusion temperature, the grains size increase, but the change is not obvious.The hardness of the alloy modified by Er, Sr and Cu are higher than the original 5052 alloy under different extrusion temperature. The hardness cures of the original 5052 and 5052 alloys modified by Sr, Cu are in V type distribution. The hardness cure of the alloy modified by Er under390 and 420℃ presents the v-shaped distribution. But under 450℃, the hardness cure distribution is W type. Under different extrusion temperature, the hardness of the alloys are improved comparedwith the as-cast alloys. The mechanical properties of the 5052 alloy modified by Er, Sr,Cu are largest at 390 ℃ and are smallest at 420℃. Under different extrusion temperature, the strength and elongation of the 5052 alloys added trace elements are higher than the original alloy. Whatever the alloy, the mechanical properties of the 5052 alloy modified by Er, Sr,Cu are largest at 390 ℃ and are smallest at 420℃.