Metallrand

Metallrand is a term used in materials science to describe a thin, continuous metallic rim that forms at boundaries within certain metallic materials during high-temperature processing or rapid solidification. The name derives from the German word for “metal edge.”

Formation and characteristics: Metallrand arises from diffusion and segregation of alloying elements at interfaces, leading to enrichment of specific elements along grain boundaries or phase boundaries. The resulting rim typically differs in composition and microstructure from the surrounding matrix. Rim thickness can range from a few micrometers up to several tens of micrometers, and its composition may include elements such as chromium, nickel, or molybdenum in steel-based systems, or aluminum and magnesium in aluminum alloys. The rim can influence mechanical properties, including hardness and brittleness, as well as corrosion resistance, acting as a diffusion barrier in some cases or as a preferential crack initiation site in others.

Occurrence and materials: Metallrand has been reported in a variety of alloys subjected to high-temperature processing, including stainless steels, nickel-based superalloys, and certain aluminum alloys. It is particularly noticeable after processes that involve rapid cooling, severe plastic deformation, welding heat-affected zones, or additive manufacturing. The prominence and effects of the rim depend on the specific alloy system and processing parameters.

Significance and study: Research on metallrand uses electron microscopy and compositional analysis to understand its impact on performance, such as fatigue life, creep behavior, and corrosion resistance. Controlling processing conditions can sometimes promote beneficial rim formation to enhance attributes, while in other cases, rim formation may be mitigated to avoid detrimental weaknesses.

See also: grain boundary, diffusion, heat treatment, additive manufacturing.