Microsegregation
Microsegregation is the chemical inhomogeneity within a dendrite grain during solidification, caused by differing solubilities.
Physico-chemical Mechanism of Action
During cooling from molten to solid metal, crystals (dendrites) form. Within these crystals, chemical components can distribute unevenly, leading to microsegregation. These inhomogeneities arise from differences in solubility of various elements in the melt and affect the local composition of the metal.
Metallurgical Relevance & Risks in Welding
Microsegregation can lead to local stress areas that can cause cracks or hot cracks in the weld. It also impairs the mechanical properties such as strength and toughness of the material. At high levels of microsegregation, the metal can become more susceptible to corrosion.
Workshop Practice & Instructions
To minimize microsegregation, it is important to ensure a homogeneous weld pool condition and controlled cooling. This can be achieved by choosing the right welding process (e.g., TIG welding for thin-walled tasks) and the correct process parameters. Uniform temperature management and careful selection of shielding gases can also help reduce microsegregation.