Hot extrusion for Al-Si-(Fe, Cu) hyper-eutectic cast alloys

For hyper-eutectic Al-Si-(Fe, Cu) cast materials in large scale ingots, we have studied microstructural modification by thermomechanical treatment to produce a heavily deformable material. Cast materials contained coarse primary Si crystals in a few hundred micron diameter or acicular intermetallic compound in several hundred micron length. Even by multiple-step cold-rolling, sample fracture of the cast alloys occurred with more extrusion step to the cast materials. A novel process, repeated thermomechanical treatment (RTMT), could be applied to extruded materials. The cold work at 77K and intermediate annealing cycle was repeated four times with 66% reduction in section