(True/False) Material fracture toughness depends on the base metal but not the weld metal.

(True/False) Material fracture toughness depends on the base metal but not the weld metal.

• A. True
• B. Not sure
• C. Both
• D. False

Answer: (D)

Fracture toughness of a welded joint comes from both the base metal and the weld region, not just the base metal. The weld metal has its own composition and microstructure, which can be different from the parent metal and can either increase or decrease toughness depending on how it’s deposited and cooled. In addition, the heat-affected zone created by welding undergoes thermal cycles that can alter grain size, phase composition, and induce residual stresses. These changes often reduce toughness in the HAZ or create brittle areas where cracks can start and propagate. Because the overall toughness of a joint is governed by the weakest region among the base metal, weld metal, and HAZ, you can’t say toughness depends only on the base metal. That’s why the statement is not correct.

Fracture toughness of a welded joint comes from both the base metal and the weld region, not just the base metal. The weld metal has its own composition and microstructure, which can be different from the parent metal and can either increase or decrease toughness depending on how it’s deposited and cooled. In addition, the heat-affected zone created by welding undergoes thermal cycles that can alter grain size, phase composition, and induce residual stresses. These changes often reduce toughness in the HAZ or create brittle areas where cracks can start and propagate. Because the overall toughness of a joint is governed by the weakest region among the base metal, weld metal, and HAZ, you can’t say toughness depends only on the base metal. That’s why the statement is not correct.