Lattice parameter variation
Lattice constant change is the variation in distances between atoms in a crystal lattice due to mechanical stresses or chemical changes.
Physical-chemical mechanism of action
The lattice constant of a material is the average distance between atoms in its crystal structure. Under mechanical stresses, such as during welding or stress build-up, this distance changes. Chemical changes, such as the introduction of foreign atoms or phase transformations, can also affect the lattice constant.
Metallurgical relevance & risks in welding
An excessive lattice constant change can lead to coarsening of the crystal lattice. This can impair the toughness and strength level of the material, increase the risk of cracking, and alter its mechanical properties. During welding, this can result from inadequate cooling or excessive stresses in the weld.
Workshop practice & instructions
To ensure minimal lattice constant change, it is important to cool the weld properly. This can be achieved through controlled cooling procedures and the use of appropriate shielding gases. For materials that are difficult to deform or when high stresses are present in the weld, careful planning of welding processes is essential.