TY - THES

T1 - Mechanical Constitution of Stable and Metastable Phases in Cu20Sn

AU - Lumper, Lea

N1 - embargoed until null

PY - 2021

Y1 - 2021

N2 - In this thesis, the Cu20Sn 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 bcc 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 available literature and the phase diagram. 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 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.

AB - In this thesis, the Cu20Sn 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 bcc 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 available literature and the phase diagram. 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 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.

KW - Nanoindentation

KW - Bronze

KW - Cu-Sn Legierung

KW - metastabile Phasen

KW - Intermetallische Phasen

KW - in-situ Charakterisierung

KW - nanoindentation

KW - bronze

KW - Cu-Sn alloy

KW - metastable phases

KW - intermetallic phases

KW - in-situ characterization

M3 - Master's Thesis

ER -