What Does Coring Mean?
Coring is a defect in an alloy (e.g., a copper nickel alloy) that occurs when a heated alloy is cooled too fast for diffusion to occur. This causes the alloy to be in a non-equilibrium condition because the exterior portion cools and solidifies before the interior portion, which remains hot and soft.
Corrosionpedia Explains Coring
Alloys must be manufactured in proper equilibrium temperature conditions to give them strength and durability.
Coring is a defect that forms in alloys due to cooling them in improper non-equilibrium temperature conditions. Coring results when more of the higher melting temperature element is retained at the center grains in an alloy. When this occurs, the dendrite arms formed from the exterior have a different composition than the alloy in the interior regions, resulting in a local compositional difference that reduces the alloy's quality and performance.
Coring can be removed by subsequent annealing and/or hot-working processes.