The metallographic sample of longitudinal section is cut from the inner rim of the spinning blank rim. The sample is ground by abrasive paper, mechanically polished by diamond polishing agent, and finally eroded by the corrosive agent. The corrosion time is 20 seconds. After the corrosion, it is washed and dried with anhydrous ethanol. The test equipment is OLYMPUS DSX500 optical microscope to observe its surrounding structure.
The microstructure of the inner rim of the wheel processed by the improved forming scheme is shown in the figure. Figure a and Figure b show the microstructure of the forming scheme A1 and A2, respectively. It can be seen that the structure near the spinning wheel area can form a good metal flow line, and the grain refinement effect is obvious, but the as-cast structure can still be seen in the middle and near the core mold area (bottom). The grain size and microstructure streamline distribution of these two layers directly determine the local performance of the inner rim. It can be seen from the figure that Scheme A1 can achieve the best deformation effect.