Transformation Plasticity
Transformation plasticity is the ability of metals to deform plastically while changing their crystal structure. This happens under low loads and leads to temporary deformations.
Physico-Chemical Mechanism of Action
During the transformation from one metal lattice to another (e.g., from austenite to martensite), the atomic arrangements change. These volume changes cause local stresses that plastically deform the material and temporarily distort it.
Metallurgical Relevance & Welding Risks
Without transformation plasticity, crack-prone microstructures can occur, especially with fast cooling. This raises the risk of hot cracking and lowers the mechanical properties of the weld.
Workshop Practice & Action Instructions
To ensure transformation plasticity, you need controlled cooling. This can be done by picking the right shielding gas and sticking to the correct welding temperature. For heavy steels (e.g., HSS), the cooling rate shouldn't be too fast to allow enough transformation plasticity.