Feedstock production by electro-magnetic stirring method for thixo-forming

The production of final parts from AA7050 Al alloy, which has a large area of use in the aerospace and aviation industry, is mostly made by machining or low/high pressure casting method. For the production of the final part, both wasted parts and time loss are quite high. This situation causes loss of profit in terms of cost in the produced part. Recently, semi-solid forming method is used in the production of parts due to its superior properties such as high mechanical properties and production of parts near net shape. The feedstock used for semi-solid forming must have thixotropic properties. There are many methods for the production of precursors with thixotropic properties. In this study, electro-magnetic stirring method was used for thixotropic feedstock production. Thixotropic feedstock was produced from AA7050 Al alloy by electro-magnetic stirring method. Electro-magnetic stirring unit was controlled by a specially written computer program. Electro-magnetic stirring unit was controlled via PLC via computer with interface created using Profi-LAB editor software. An asynchronous motor is used to create a variable magnetic field and the motor is controlled by a frequency converter. During the solidification in the semi-solid temperature range, three different samples were produced with different parameters by electro-magnetic stirring method. For comparison purposes, graphite mold casting was carried out under the same conditions without electro-magnetic stirring. Microstructures of all produced samples were examined. At the end of the microstructure investigations, it was observed that the α-Al dendrite arms were broken and the α-Al grains in the microstructure had rosette and/or rarely spherical shape in the thixotropic AA7050 samples produced by the electro-magnetic stirring method. When the sample produced by the graphite mold casting method without electro-magnetic stirring was examined, it was determined that the α-Al grains in the microstructure were formed dendritic. When all samples were examined, ideal thixotropic feedstock production was achieved with frequency 50 Hz, voltage 380 volts, torque 160 N/m