Substitutional solid solution
Substitutional solutions are formed when alloying atoms enter and reside at regular lattice sites of the base metal. This happens when atomic radii are similar.
Physical-Chemical Mechanism of Action
In a substitutional solution, alloying atoms enter the lattice of the base metal and occupy regular crystal lattice sites. This is possible when the atomic radii of the alloying atoms do not differ greatly from those of the base metal. The penetration leads to a change in the crystal structure and properties of the material.
Metallurgical Relevance & Welding Risks
Substitutional solutions affect the mechanical properties of the steel, such as strength and durability. Too high a concentration of alloying atoms can lead to coarsening and degradation. If the welding temperature or time is wrong, porosity can occur, affecting hardness and microstructure.
Workshop Practice & Action Points
To create a stable substitutional solution, pay attention to the correct alloy composition and welding temperature. Avoid excessive concentrations of alloying atoms. During cooling, it's important to stay within the critical temperature window (e.g., t8/5 between 5 and 25 seconds) to ensure a homogeneous crystal structure.