Residual Phase Proportion
The residual phase fraction indicates how much metastable microstructural constituents are still present in a weld that have not been fully transformed. This affects long-term behavior and toughness under load.
Physical-Chemical Working Mechanism
After welding, part of the old base structure in the weld remains metastable, i.e., it hasn't fully transformed to the new structure. This fraction is called the residual austenite content.
Metallurgical Relevance & Welding Risks
High residual austenite content can cause long-term failure and reduced toughness, as these metastable phases don't deform as well under load as fully transformed ones. This raises the risk of cracking and wear.
Shop Practice & Action Guidelines
To minimize residual austenite, careful post-weld heat treatment is essential. This includes proper cooling steps and weld integrity testing. For highly stressed applications, ensure a very low residual austenite content of ≤5%.