Effects of homogenization on the dissolution and precipitation behaviors of intermetallic phase for a Zr and Er containing Al-Zn-Mg-Cu alloy

The effects of homogenization on dissolution and precipitation behaviors of intermetallic phase in a novel Zr and Er containing Al-Zn-Mg-Cu alloy were investigated. In this work, single-stage (SS:475 degrees C/24 h) and doublestage (DS:400 degrees C/12 h + 475 degrees C/24 h) homogenization treatments were carried out for the ingots with the heating rates of 300 degrees C/h, 50 degrees C/h and 25 degrees C/h, respectively. It was found that Er tended to segregate at the grain boundary in the form of Al8Cu4Er, and the formation mechanism was determined to be the eutectic reaction in the front of the solid/liquid interface during solidification. Also, Al8Cu4Er phase was detected to possess high melting point (similar to 573.8 degrees C), which fully remained after the homogenization. Meanwhile, a significant impact of heating rate on the dissolution of intermetallic phases for the studied alloy under the DS homogenization was determined, but little impact was observed under the SS homogenization. Morever, the size and distribution of the dispersoids after homogenization were fully analyzed. It was found that slow heating rates was helpful to refine the particles size, and increase the density as well as volume fraction of the precipitation under both SS and DS homogenization. However a higher density and volume fraction of the precipitated particles, and a relatively larger average particle size were gained with DS homogenization.