EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Bronze alloys, i.e. Cu-Sn alloys, exhibit up to nine different phases according to the phase diagram. Although known for decades, those phases are barely mechanically investigated. Thus, in this work, a Cu 20 m.% Sn alloy was intensively investigated with various experimental techniques to gather the existing knowledge about the Cu-Sn system with a particular focus on the properties of the appearing phases. Numerous heat treatments were executed in order to investigate the emerging stable and metastable phases by microscopy and electron diffraction. Several phases, including a Cu solid-solution α, the high-temperature body-centered crystal β as well as several intermetallic (γ, δ, and ε) phases could be set to investigate at room temperature. Crystallography, chemical composition, and phase fraction of the investigated samples were discussed with respect to the available literature. Additionally, high-temperature calorimetry and in-situ X-ray diffraction experiments were performed to further characterize the alloy with respect to its thermal stabilities. It was found that depending on the appearing phases the thermal stability strongly varies.
To characterize the mechanical properties of the individual different phases, advanced nanoindentation techniques were applied at room and elevated temperatures. The obtained results correlate well with the respective crystal structure and Sn-content of each phase. Additionally, the high-temperature mechanical properties of the indented phases reveal a strong thermal activation of flow stress, either caused by a complex crystal lattice or the increased diffusivity of Sn in the solid solution.