Fraunhofer Institute for Mechanics of Materials IWM
Copper-beryllium alloys (Cu-Be) are characterized by their high strength and electrical conductivity and are therefore often used in electrical connectors. However, beryllium is harmful to health and is produced in only a few countries outside Europe, creating a supply risk. There is therefore a strong need to find alternatives that retain the excellent properties of Cu-Be alloys. Fraunhofer IWM has taken on this challenge in a project with other research institutes and industry partners and has identified Cu-Ni-Al alloys as promising substitute materials.
The materials science challenge lies particularly in the microstructure-based modeling of high-temperature strength. It is crucial to understand the complex interactions between the process parameters and the resulting materials properties in order to achieve the desired microstructure. This requires precise control of microstructure development and mechanical properties during heat treatment to achieve optimal properties such as increased hardness and improved wear resistance.
In the case of Cu-Ni-Al alloys, high strength is achieved through the formation of fine L12 phase (Ni, Cu)3Al precipitates with a size of 10 nm to 20 nm. These precipitates hinder dislocation motion in the lattice and lead to the strengthening of the alloy. Through thermodynamic-kinetic calculations, the radius of these precipitates can be precisely predicted and integrated into a model that describes the yield strength and creep properties of the alloys. This theoretical understanding is crucial for making targeted substitutions.