Grain Boundary
The grain boundary is the boundary point between differently oriented crystal grains, which impedes deformation and makes the material susceptible.
Physical-Chemical Mechanism
The grain boundary forms at the contact between two different crystal grains in the metal structure. This interface can act as an obstacle to the sliding movement of atoms because the crystal structure is differently oriented.
Metallurgical Relevance & Risks in Welding
If the grain size is too large and there are many grain boundaries, the material becomes susceptible to fatigue and cracking. This can lead to fractures, especially under high stresses or in complex components.
Workshop Practice & Action Instructions
To minimize grain boundaries, it is important to create a homogeneous weld zone. This can be achieved by careful control of welding parameters and the use of stabilizing additions. For steel, apply a grain refiner before welding to reduce grain size.