The evolution of semi-solid microstructure in 7075 aluminum alloy extruded bar was investigated by three stages induction heating.A semisolid thixoforming mold for a certain type of fin structure was designed.The microstructure of 7075 high-strength aluminum alloy tail fin made by semisolid thixotropy-plastic composite near net forming was observed by OM and SEM.With the average heating speed of 4 ℃/s

the highest heating temperature at upper end of the billets of 620 ℃ for 5 min

the complex thin-walled position at the workpiece presents complete shape and high dimensional accuracy

and the microstructure of its longitudinal section is the gradient microstructure of semi-solid to solid state.