Effect of Homogenization Heat Treatment on Elongation Anisotropy in Cold-Rolled and Annealed Al-Si Alloy Sheets Fabricated from Vertical-Type High-Speed Twin-Roll Cast Strips

Vertical-type high-speed twin-roll casting (VT-HSTRC), which is characterized by a high production rate and cooling rate, is a promising method for upgrade recycling of aluminum cast alloy scrap to wrought alloys in the near future. To produce wrought alloy sheets from cast alloy scrap, the strips must be isotropic to achieve good formability. However, in cold-rolled and annealed Al-7% Si alloy and A356 alloy sheets fabricated from the HSTRC strips, average elongation is much greater in the rolling direction than in the transverse direction. This elongation anisotropy results from both the morphology and the alignment of eutectic Si particles. In the present study, the effect of homogenization heat treatment on the microstructure and elongation was investigated. Al-7% Si and Al-11% Si alloy strips were fabricated by HSTRC and were homogenized by heat treatment at 540 ℃ for 10 h and 500 ℃ for 10 h, respectively. The strips were cold rolled at a reduction rate of 50% and annealed. The eutectic Si particles were spheroidized and coarsened by the homogenization heat treatment, and they were uniformly dispersed after cold rolling. There was no significant difference in elongation between the rolling and transverse directions in the Al-7% Si and Al-11% Si alloys. These results show that the homogenization heat treatment of the strips reduced the elongation anisotropy.