High-resolution electron microscope observation of interface microstructure of a cast Al-Mg-Si-Bi-Pb(6262)/Al2O3p...

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Advanced aluminum composites are crucial for lightweight applications.
• Understanding interfacial reactions is key to optimizing composite properties.
• Alloying elements like Mg, Si, Bi, and Pb influence composite performance.

Purpose of the Study:

• To characterize the interface structure of cast Al-Mg-Si-Bi-Pb aluminum composites reinforced with alpha and beta alumina.
• To investigate the behavior and distribution of alloying elements (Bi, Pb) at the composite interfaces.
• To determine the reaction products and orientation relationships at the Al/alumina interfaces.

Main Methods:

• High-resolution electron microscopy was utilized for detailed interface characterization.
• Analysis focused on the interfaces between the aluminum matrix and alpha-alumina and beta-alumina reinforcements.
• The distribution and form of alloying elements (Bi, Pb) were examined.

Main Results:

• Limited reaction products were observed at the Al/alpha-Al2O3 interface due to unfavorable kinetics during squeeze casting.
• Significant MgAl2O4 formation occurred on beta-Al2O3 surfaces, with a specific orientation relationship.
• Bismuth (Bi) and lead (Pb) were identified as metallic nanoparticles within the aluminum matrix at various interfacial locations.

Conclusions:

• The interface structure is dominated by energy minimization, leading to parallel close-packed planes and directions.
• Beta-alumina's crystal structure facilitates MgAl2O4 nucleation and growth.
• Bismuth and lead segregate as nanoparticles, potentially influencing the composite's mechanical and physical properties.