Dispersoids in Al-Mg-Si Alloy AA 6086 Modified by Sc and Y

Area of Science:

• Materials Science
• Metallurgy
• Alloy Development

Background:

• Aluminum alloy AA 6086 is recognized for its superior room temperature strength within the Al-Mg-Si family.
• Enhancing high-temperature strength in aluminum alloys is crucial for demanding applications.
• L1₂-type dispersoids are known to improve the high-temperature mechanical properties of alloys.

Purpose of the Study:

• To investigate the impact of Scandium (Sc) and Yttrium (Y) additions on dispersoid formation in AA 6086.
• To characterize the formation mechanisms and kinetics of L1₂ dispersoids, particularly during thermal treatments.
• To evaluate the effect of Sc and Y on the hardness and high-temperature strength of AA 6086.

Main Methods:

• Comprehensive material characterization using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
• Chemical analysis via energy dispersive spectroscopy (EDS).
• Crystallographic analysis using X-ray diffraction (XRD).
• Thermal analysis employing differential scanning calorimetry (DSC) and dilatometry.

Main Results:

• Sc and Y additions induced the formation of L1₂ dispersoids during heating, homogenization, and isothermal heat treatments (T5 temper).
• Dispersoid formation was observed in both homogenized and as-cast conditions.
• The highest hardness in Sc and (Sc + Y) modified alloys was achieved through T5 temper heat treatments between 350 °C and 450 °C.

Conclusions:

• Scandium and Yttrium are effective in promoting the formation of beneficial L1₂ dispersoids in AA 6086.
• These dispersoids contribute to increased hardness and potentially improved high-temperature strength.
• Optimized heat treatment in the 350-450 °C range for as-cast alloys yields maximum hardness.