Characterisation of the material interface in multi-material additive manufacturing

Abstract

The aim of this work is the characterisation of the interface of a bimetallic material composed of Cu-Cr-Zr, a copper alloy known for its good thermal conductivity, and maraging steel, well known for its good mechanical properties. This combination will be done thanks to laser powder bed fusion technique. The pieces are produced in a 3D printer that comes from ”Aquanity” with a printing head developed by Aerosint. The first part of the project is the determination of the printing parameters of each material alone. This determination is done thanks to porosity measurements on optical microscope and density measurements on pycnometer. The relative density obtained reaches more than 99.9% for both materials. Once the printing parameters have been determined, the interface is analysed thanks to optical and electronic microscopy. The vertical as well as the horizontal interface were analysed. Leading to satisfying results for the second one and unsatisfying results for the first one. These unsatisfying results are linked to cracks and lacks of fusion appearance as well as massive material mixing next to the vertical interface. The horizontal interface have been analysed with maraging steel above Cu-Cr-Zr and with Cu-Cr-Zr above maraging steel, showing satisfying results in both configurations.Lastly, the thermal properties of Cu-Cr-Zr as well as the mechanical properties of maraging steel were measured before and after heat treatment. The heat treatment performed is an ageing treatment with an ageing temperature of 520°C and an ageing time of one hour. This heat treatment leads to an increase of 50% in hardness of maraging steel and an increase of 200% in thermal diffusivity of Cu-Cr-Zr. Showing a clear effectiveness of the heat treatment. The thermal diffusivity of the bimetallic material was measured as well before and after heat treatment.