# Optimizing the Performance of Window Frames: A Comprehensive Review of Materials in China
## 3 Improvement Methods and Sustainability Assessment
### Metal
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Series** & **Main Alloying Element (s)** & **Main Characteristics** & **Example Applications** \\ \hline \multirow{2}{*}{1 xxx} & \multirow{2}{*}{Pure aluminum} & High electrical and thermal & \multirow{2}{*}{Big electrical rotors.} \\  & & conductivity; excellent corrosion & \\  & & resistance. & \\ \hline \multirow{2}{*}{2 xxx} & \multirow{2}{*}{Copper} & High strength & \multirow{2}{*}{Cylinder heads and pistons, housing} \\  & & But low corrosion resistance. & & and bearings \\ \hline \multirow{2}{*}{3 xxx} & Silicon, copper and/or & High strength and wear resistance; & \multirow{2}{*}{Motor parts, structural parts, and} \\  & magnesium & good corrosion resistance. & & marine and aircraft castings. \\ \hline \multirow{2}{*}{4 xxx} & Silicon & Moderate strength; high ductility; good & \multirow{2}{*}{Bridge railing support castings, dental} \\  & & impact resistance & & equipment, and cookware. \\ \hline \multirow{2}{*}{5 xxx} & \multirow{2}{*}{Magnesium} & Moderate to high strength; high & \multirow{2}{*}{Architectural and ornamental castings} \\  & & corrosion resistance; good & & and welded assemblies. \\  & & machinability; attractive appearance. & & \\ \hline \multirow{2}{*}{7 xxx} & \multirow{2}{*}{Zinc} & Good finish; good corrosion resistance; & \multirow{2}{*}{Automotive parts and mining} \\  & & high strength through heat treatment. & equipment. \\ \hline \multirow{2}{*}{8 xxx} & Tin & Low friction. & Bearing and bushing applications. \\ \hline \multirow{2}{*}{1 xxx} & \multirow{2}{*}{Pure aluminum} & High electrical and thermal & \multirow{2}{*}{Electrical conductors and chemical  processing equipment.} \\  & & conductivity; excellent corrosion & & \\ \hline \multirow{2}{*}{2 xxx} & \multirow{2}{*}{Copper} & High strength-to-weight ratio; low & \multirow{2}{*}{Truck wheels and suspensions, aircraft} \\  & & corrosion resistance. & fuselage and wings. \\ \hline \multirow{2}{*}{3 xxx} & Manganese & Moderate strength and good & \multirow{2}{*}{General sheet work, recreation vehicles, and electronics.} \\  & & workability. & & \\ \hline \multirow{2}{*}{4 xxx} & Silicon & Low melting point and thermal & \multirow{2}{*}{Welding wire and brazing alloy, architectural applications, and forged  engine pistons.} \\  & & expansion; high wear resistance. & & \\ \hline \multirow{2}{*}{5 xxx} & Magnesium & Moderate to high strength; good & \multirow{2}{*}{Appliances, automotive parts, and  marine components.} \\  & & weldability; good corrosion resistance. & & \\ \hline \multirow{2}{*}{6 xxx} & \multirow{2}{*}{Silicon and magnesium} & Medium strength with good & \multirow{2}{*}{Structural applications, architectural  extrusions, and recreational equipment.} \\  & & formability; weldability, machinability; & \\ \hline \multirow{2}{*}{7 xxx} & \multirow{2}{*}{Zinc} & Moderate to very high strength. & \multirow{2}{*}{Airframe structures, mobile equipment, and high-stress parts.} \\  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: A series of aluminum alloys about cast aluminum and forged aluminum (adapted from [107]). * Corrosion To prevent the corrosion of aluminum alloys, surface treatments such as anodization [108], painting [109], or coating [110] can be applied, as shown in Table 3. Anodization is a process that significantly enhances the corrosion resistance of aluminum alloys. Anodization involves passing a current through aluminum while immersing it in an electrolytic solution; this results in the formation of a thicker and more durable oxide layer on the surface of aluminum, providing enhanced corrosion protection [111]. Additionally, aluminum alloys can be alloyed with elements such as copper, magnesium, or zinc, further enhancing their corrosion resistance [102; 112]. * Thermal The heat transfer in window frames primarily occurs through the solid's thermal conductivity, as well as convective and radiative heat transfer within the cavities [114].