In the Heat Affected Zone HAZ of a weld how is the microstru

In the Heat Affected Zone (HAZ) of a weld, how is the microstructure and mechanical properties (specifically strength and ductility) of a metal affected?

Solution

During fusion welding material close to welds experience a large thermal fluctuations. Some metallurgical changes in HAZ do occur. These may be major matrix phase change or precipitation process. Even in material showing no phase change or precipitation during welding recrystallisation and grain growth may occur. The HAZ has an important role to determine the weld cold cracking , notch toughness , stress corrosion cracking etc, .

Strength depends upon the how the original strength of the particular alloy were developed prior to welding , they may have been developed by cold working solution strengthening , precipitation hardening etc,. Ductility may be incresed or decreased it depends upon the type of material is going to weld .