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Clemens, Helmut

Kappacher, Johann

Lumper, Lea

Maier-Kiener, Verena

English

Engineering Conferences International

Thursday, October 6, 2022                                           Session IX: Grain Boundaries and Phase Transformations PHASE TRANSFORMATIONS AND LOCAL DEFORMATION MECHANISMS – A CASE STUDY ON CU 20 M.% SN  Lea Andrea Lumper, Department of Materials Science, Montanuniversität Leoben, Leoben, Austria lea.lumper@unileoben.ac.at Johann Kappacher, Department of Materials Science, Montanuniversität Leoben, Leoben, Austria Helmut Clemens, Department of Materials Science, Montanuniversität Leoben, Leoben, Austria Verena Maier-Kiener, Department of Materials Science, Montanuniversität Leoben, Leoben, Austria   Key Words: Cu-Sn Alloy, High-Temperature Nanoindentation, High-Energy X-Ray Diffraction, Phase Transformation  Bronze, a Cu-Sn alloy, has numerous applications, ranging from electrical components to alloys used in musical instruments. This evidences that this material exhibits a broad spectrum of properties. Particularly beneficial for adjusting the properties are the occurring intermetallic phases and the accompanying phase transformations [1]. Thereby one major task of this work is to investigate the local mechanical properties as a function of temperature. As the intermetallic phases β, γ, and δ have not been mechanically characterized in literature, high-temperature nanoindentation (HT NI) presents itself as a versatile measurement approach [2]. Not only conventional mechanical properties, such as hardness and modulus can be studied temperature-dependent via HT NI, but also thermally activated mechanical properties such as strain-rate dependence and the associated activation volume can be investigated: This correspondingly allows conclusions on the prevailing rate-controlling deformation mechanisms and the change in these depending on the individual phases.   In this work, the Cu-20 m.% Sn alloy was studied in detail with respect to its thermal properties and correlated to its mechanical properties. First, in-situ investigations were carried out utilizing high-temperature X-ray diffraction and high-temperature scanning electron microscope up to a temperature of 535 °C. Two metastable, previously unreported phases, here called HEXβ and HEXγ, were discovered in the temperature range between 160 and 340 °C. Further, these phases, as well as the intermetallic high-temperature phases β, γ, and δ, were characterized by HT NI up to 535 °C. It is found that the high-temperature β and γ phases have similar properties, as both resemble a body-centered cubic structure and thus the so-called double-kink mechanism is rate-controlling during deformation. The crystallographically very complex δ phase shows face-centered cubic-like and therefore temperature-activated deformation behavior. The results indicate that the newly discovered metastable phases exhibit similar properties as the equilibrium δ phase.  Summarized, the Cu-20 m.% Sn alloy, including its intermetallic phases, was characterized regarding their thermal stability and mechanical properties. Two metastable phases were detected and mechanically characterized together with the intermetallic phases β, γ, and δ up to 535 °C.    References  [1] Fürtauer S, Li D, Cupid D, Flandorfer H. The Cu-Sn phase diagram, Part I: New experimental results. Intermetallics 2013;34:142–7. https://doi.org/10.1016/j.intermet.2012.10.004. [2] Kappacher J, Tkadletz M, Clemens H, Maier-Kiener V. High temperature nanoindentation as a tool to investigate plasticity upon phase transformations demonstrated on Cobalt. Materialia 2021;16. https://doi.org/10.1016/j.mtla.2021.101084.    

Phase transformations and local deformation mechanisms - A case study on Cu 20 m.% Sn

https://dc.engconfintl.org/cgi/viewcontent.cgi?filename=0&article=1047&context=nanomechtest_viii&type=additional

Phase transformations and local deformation mechanisms - A case study on Cu 20 m.% Sn

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Engineering Conferences International