TY - THES

T1 - Simultaneously increasing strength and ductility of nano-crystalline Cu-Zn-alloys made from powderous raw materials

AU - Holub, Georg

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Nano-crystalline materials produced by severe plastic deformation tend to exhibit superior strength compared to their coarse-grained counterparts. Their ductility, however, stays disappointingly low. Studies have shown that alloying can reduce the stacking fault energy, thus enable additional deformation mechanisms, such as mechanical twinning. Building on former investigations of Zhao et al., this work shows the utilization of this principle for samples produced by ball milling and high-pressure torsion. Powders in compositions of pure Cu, and Cu with 10, 20, and 30 wt.% Zn were used as raw materials. Saturation of the microstructure was determined by Vickers hardness measurements and by scanning electron microscope imaging, while the grain size was analyzed by transmission electron microscopy investigations. Further, tensile tests were performed to measure the mechanical properties. Despite the same compositions and therefore the same stacking fault energies as in the references, the fabricated samples showed smaller mean grain sizes and an increased tendency for twinning. Thus, improved values for yield-strength and ultimate strength for compositions up to 20 wt.% Zn, as well as significantly higher total elongations for compositions up to 10 wt.% Zn could be achieved.

AB - Nano-crystalline materials produced by severe plastic deformation tend to exhibit superior strength compared to their coarse-grained counterparts. Their ductility, however, stays disappointingly low. Studies have shown that alloying can reduce the stacking fault energy, thus enable additional deformation mechanisms, such as mechanical twinning. Building on former investigations of Zhao et al., this work shows the utilization of this principle for samples produced by ball milling and high-pressure torsion. Powders in compositions of pure Cu, and Cu with 10, 20, and 30 wt.% Zn were used as raw materials. Saturation of the microstructure was determined by Vickers hardness measurements and by scanning electron microscope imaging, while the grain size was analyzed by transmission electron microscopy investigations. Further, tensile tests were performed to measure the mechanical properties. Despite the same compositions and therefore the same stacking fault energies as in the references, the fabricated samples showed smaller mean grain sizes and an increased tendency for twinning. Thus, improved values for yield-strength and ultimate strength for compositions up to 20 wt.% Zn, as well as significantly higher total elongations for compositions up to 10 wt.% Zn could be achieved.

KW - copper alloys

KW - stacking fault energy

KW - mechanical twinning

KW - strength

KW - ductility

KW - high-pressure torsion

KW - ball milling

KW - Kupferlegierungen

KW - Stapelfehlerenergie

KW - mechanische Zwillingsbildung

KW - Festigkeit

KW - Duktilität

KW - Hochdruck-Torsionsumformung

KW - Kugelmühle

U2 - 10.34901/MUL.PUB.2023.13

DO - 10.34901/MUL.PUB.2023.13

M3 - Master's Thesis

ER -