Incoherent Phase Boundary
Incoherent phase boundaries are interfaces between metal phases with strongly different crystal structures and lack of atomic continuity. They form through rapid cooling or uneven melting processes.
Physicochemical Mechanism of Action
Incoherent phase boundaries arise when metal phases with different crystal structures rapidly transform into one another. The atomic arrangement in the two phases does not match, leading to a lack of atomic continuity. This is similar to a high-angle grain boundary (TIG), where the crystal axes are strongly inclined to each other.
Metallurgical Relevance & Risks in Welding
Incoherent phase boundaries can lead to increased toughness and improved mechanical properties, as they prevent crack propagation. However, they can also lead to stress buildup, especially when the material is under mechanical load. These stresses can lead to cracking or damage, especially at high temperatures or under uneven load distributions.
Workshop Practice & Action Guidelines
To create incoherent phase boundaries, it is important to ensure controlled cooling and uniform melting processes. This can be achieved by selecting the right welding process (e.g., TIG welding) and the correct process parameters (temperature, time, gas composition). For steels with high carbon or silicon content, special attention must be paid to rapid cooling to promote incoherent phase boundaries.