Solidified Retained Austenite
Crystallized retained austenite is a finely dispersed, face-centered cubic (fcc) phase in weld zones that forms due to high alloy concentrations and slow cooling. It can lead to toughness loss and cracking.
Physical-Chemical Mechanism of Action
Crystallized retained austenite forms through the slow cooling of weld zones where certain alloy concentrations remain above the austenite melting point. This leads to the fine crystallization of the fcc lattice.
Metallurgical Relevance & Risks in Welding
Crystallized retained austenite can reduce the toughness of the weld and lead to cracks and hot cracks. It is particularly dangerous in highly stressed applications as it significantly impairs mechanical strength.
Workshop Practice & Instructions
To avoid crystallization, the weld should be cooled as quickly as possible. This can be achieved through high coolant water flow or the use of cooling gases. A typical target is a cooling time of t8/5 under 10 seconds to minimize the risk of crystallization.