Monotectic Reaction
Monotectic reaction: On cooling a liquid phase, a new solid phase and a second, chemically different liquid phase form. This occurs in miscibility gaps.
Physico-chemical mechanism of action
During the monotectic reaction, a liquid phase condenses into a solid phase upon cooling, while simultaneously a second, chemically different liquid phase forms. This process occurs in systems with miscibility gaps, where different metals or alloys interact.
Metallurgical relevance & risks in welding
The monotectic reaction can cause phase transformation problems, leading to uneven stress and cracks in the weld. It is particularly dangerous when joining steels with different filler materials or alloys.
Workshop practice & instructions
To avoid monotectic reactions, cooling of the weld should be controlled and slow. Use suitable filler metals or insulating materials to minimize miscibility gaps. For special alloy combinations, prior material testing is essential.