Effect of one-step and two-step homogenization treatments on distribution of Al3Zr dispersoids in commercial AA7150 aluminium alloy
(1. School of Materials Science and Engineering, Harbin University of Science and Technology,
Harbin 150080, China;
2. Northeast Light Alloy Co Ltd., Harbin 150060, China;
3. ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering,
Monash University, Melbourne VIC 3800, Australia)
Harbin 150080, China;
2. Northeast Light Alloy Co Ltd., Harbin 150060, China;
3. ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering,
Monash University, Melbourne VIC 3800, Australia)
Abstract: Semi-quantitative electron probe microanalysis (EPMA) mapping, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study the effect of one-step and two-step treatments on the Zr distribution and Al3Zr dispersoid characteristics in as-cast commercial AA7150 aluminum alloy. It is shown that the Zr concentration in the dendrite centre regions is higher than that near the dendrite edges in the as-cast condition, and that homogenization at 460 °C for 20 h is insufficient to remove these concentration gradients. After homogenizing at 460-480 °C, a high number density of larger dispersoids can be observed in dendrite centre regions but not near dendrite edges. Furthermore, the dispersoid size increases with increasing the temperature during both one-step and two-step homogenization treatments.
Key words: 7xxx alloy; AA7150 alloy; homogenization; recrystallization; Al3Zr dispersoids; concentration gradient