Deformation-Induced Phase Transformation
Deformation-induced phase transformation: Austenite transforms to martensite due to mechanical stress, increasing work hardening and energy absorption capacity.
Physical-Chemical Mechanism of Action
Mechanical stress triggers local stresses in austenite, a metastable phase. These stresses can influence the atomic structure, causing transformation to martensite. This process is supported by rapid cooling and the occurrence of shear stresses.
Metallurgical Relevance & Welding Risks
Deformation-induced phase transformation increases the material's work hardening, resulting in increased hardness and a lower elastic modulus. This can lead to cracks and fractures under further load. Additionally, the energy absorption capacity can increase, raising the risk of hot cracking and damage under mechanical load.
Workshop Practice & Action Guidelines
To minimize deformation-induced phase transformation, it is important to cool the material after welding in a controlled and slow manner. This can be achieved using cooling water or oil. For highly stressed materials like high-performance nickel alloys, a specific cooling curve should be set to reduce the risk of cracking. It is also important to minimize mechanical stress during and after welding.