Phase Boundary Coherency
The seamless joining of crystal lattices of different phases. Creates elastic stress fields that increase strength.
Physical-chemical mechanism of action
The coherence of the phase boundary refers to the seamless connection of crystal lattices of different metals or alloys. This happens through a continuous arrangement of atoms, so that no atomic dislocations occur.
Metallurgical relevance & risks in welding
High coherence at phase boundaries increases the strength and toughness of the weld. However, too much coherence can lead to stress buildup, which can cause cracks or hot cracks in the material. This is especially relevant at high temperatures and rapid cooling.
Workshop practice & instructions
To ensure optimal coherence at phase boundaries, the weld should be cooled as quickly as possible (t8/5 < 10 s) to minimize stress buildup. At high carbon contents, it is important to ensure sufficient deoxidation to avoid porosity.