To avoid stress corrosion cracking, the filler alloy used for elevated temp application is AA-5554, which has 3% max Mg.

To avoid stress corrosion cracking, the filler alloy used for elevated temp application is AA-5554, which has 3% max Mg.

• A. AA-5554
• B. AA-5356
• C. AA-5454
• D. AL-Si Filler Alloys

Answer: (A)

Stress corrosion cracking in aluminum welds is driven by the combination of residual tensile stresses, a corrosive environment, and a susceptible weld metal composition. In hot service, diffusion and precipitation processes can accelerate cracking, so using a filler with a composition that minimizes these driving forces reduces the risk. AA-5554 is a low-magnesium filler (maximum about 3% Mg). Keeping Mg content limited helps keep the weld metal chemistry closer to the base 5xxx alloys and reduces galvanic differences and embrittlement tendencies at elevated temperatures, lowering SCC susceptibility while still providing good weldability and corrosion resistance. Other fillers in the 5xxx family with higher Mg contents tend to increase SCC risk in elevated-temperature service, and fillers with significantly different alloying systems (such as silicon-rich or non-Mg fillers) don't provide the targeted compatibility and corrosion behavior needed for avoiding SCC in hot environments. Therefore AA-5554 with its restrained Mg content is the best choice for elevated-temperature applications where avoiding stress corrosion cracking is a priority.

Stress corrosion cracking in aluminum welds is driven by the combination of residual tensile stresses, a corrosive environment, and a susceptible weld metal composition. In hot service, diffusion and precipitation processes can accelerate cracking, so using a filler with a composition that minimizes these driving forces reduces the risk. AA-5554 is a low-magnesium filler (maximum about 3% Mg). Keeping Mg content limited helps keep the weld metal chemistry closer to the base 5xxx alloys and reduces galvanic differences and embrittlement tendencies at elevated temperatures, lowering SCC susceptibility while still providing good weldability and corrosion resistance.

Other fillers in the 5xxx family with higher Mg contents tend to increase SCC risk in elevated-temperature service, and fillers with significantly different alloying systems (such as silicon-rich or non-Mg fillers) don't provide the targeted compatibility and corrosion behavior needed for avoiding SCC in hot environments. Therefore AA-5554 with its restrained Mg content is the best choice for elevated-temperature applications where avoiding stress corrosion cracking is a priority.