Microvoid Coalescence
Microvoid coalescence is a ductile fracture process where microscopic voids form and grow at inclusions until they link up to form a continuous crack surface. This results in the dimpled appearance of the fracture.
Physicochemical mechanism of action
Micro-void coalescence occurs due to the accumulation of voids at micro-segregations and inclusions in the material. These voids grow continuously until they form a connected fracture surface. The process is triggered by mechanical loads and thermal stresses.
Metallurgical relevance & risks in welding
This process can lead to severe ductile fracture of the weld, especially if the material is rich in micro-segregations or inclusions. The dimpled structure of the fracture surface indicates micro-void coalescence and can lead to cracks and deformation in the component.
Workshop practice & actions to take
To avoid micro-void coalescence, it is important to ensure a clean weld pool and proper cooling. Use a stable welding process and pay attention to the hardness of the material. For fine inclusions, high stress or slow cooling can also help slow down void growth.