Monotectic reaction
Monotectic is a solidification reaction where a homogeneous liquid splits into two different phases upon cooling: one solid and one second liquid. It occurs in alloy systems with a tendency for phase separation in the melt.
Physical-Chemical Mechanism of Action
In monotectic, when a homogeneous liquid cools, a two-phase mixture of solid and liquid forms. This occurs when the alloy contains different chemical components in the melt that arrange differently at lower temperatures.
Metallurgical Relevance & Risks in Welding
Monotectic can lead to uneven solidification and phase boundary defects. This can make the weld porous or cause cracks. It also increases susceptibility to hot cracking and alters the mechanical behavior of the alloy.
Workshop Practice & Instructions
To avoid monotectic, it is important to set the melting temperature precisely and carry out controlled cooling steps. For special alloys, slow cooling or the use of coolants may be required. It is also helpful to know the melt composition and take appropriate samples.