| Title |
A Study on the Variation of Microstructure During Reheating an Electromagnetically Stirred A1-4.5 wt%Cu Alloy |
| Authors |
조강래(Kang Rae Cho),김정호(Jeong Ho Kim),김경민(Kyoung Min Kim),김기배(Ki Bae Kim),윤의박(Eui Pak Yoon) |
| Abstract |
Electromagnetically stirred Al-4.5 wt%Cu alloy was reheated into semi-solid state by precisely temperature-controllable gold image furnace. Evolution of microstructures in the semi-solid state was investigated with fixed reheating rate, various holding time and holding temperature. The interface of cells consisting of primary particle formed by electro-magnetic stirring disappeared due to particle regrowth during reheating the alloy. Particle with entrapped eutectic appeared by the coarsening of dendrite which was preciously formed by rapid cooling of residual liquid after stirring stopped and entrapped eutectic changed into K phase by diffusion mechanism as holding time increased. Particles were coarsened, showing polygonal shape and the solute content of solid particle(K phase) increased by redistribution of solute between solid particle and liquid phase, as holding time increased more. Liquid fraction was 11.6% at 637℃ when the alloy was held for 420 minutes, although it is expected 50% by Scheil equation. It was thought that particle coarsening resulted from simple particle growth, coalescence, Ostwald ripening during reheating the electromagnetically stirred Al-4.5 wt%Cu alloy. |