Subgrain Boundary Formation
Subgrain boundary formation is the division of crystallites into smaller regions by dislocations during recovery. This reduces grain size and can lead to improved toughness.
Physicochemical Mechanism of Action
Subgrain formation occurs when dislocations in the crystallites arrange during the recovery phase. These dislocations form network-like walls that subdivide the crystallite into smaller, weakly misoriented regions.
Metallurgical Relevance & Welding Risks
Subgrain formation can lead to improved toughness and increased strength levels. However, it can also increase susceptibility to cracks and hot cracking if the dislocations are not arranged properly.
Workshop Practice & Action Instructions
To promote subgrain formation, control the molten pool temperature profile and keep it slow. Rapid cooling can prevent proper dislocation arrangement and lead to cracking. Recommended cooling times vary by steel type, but generally should be between 10 and 30 seconds.