Correlation of Fine Scale Microstructure and Mechanical …
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by x-ray diffraction (XRD) using a Rigaku 18 kW x-ray generator and a highresolution powder diffractometer utilizing Cu-Kα 1 . For TEM, samples were prepared
by initially polishing the disk samples mechanically and finally by thinning in an ion
mill with a gun voltage of 4 kV and a sputtering angle of 10°. Tecnai G
2 analytical
transmission electron microscope operating at 300 keV was used to characterize the
microstructure and dislocations. Furthermore, a JEOL 2200 analytical transmission
electron microscope operating at 200 keV was used to characterize the microstructure
and interfacial characteristics of the oxide particulates. To investigate the mechanical
behavior, micro and nano indentation hardness tests were performed to obtain hardness and elastic modulus of copper-alumina composite. For micro-hardness, Vickers
tip at 200 gm of load and dwell time of 15 s was used. To investigate mechanical
behavior, nano indentation hardness tests were performed with a Berkovich indenter
to obtain hardness values of the composites and commercially pure copper.
Results and Discussion
A bright-field TEM image (see Fig. 1a) shows the elongated grains of the copperalumina composite as a result of cold work. This increases the tensile and yield
strengths by introducing high density of dislocations. Furthermore, a very fine dispersion of oxide particles in the size range of 5–10 nm has been observed in the matrix.
These oxide particles in copper matrix originate from the internal oxidation process of
copper matrix at elevated temperatures. In this process, initially, the powder is heated
in a controlled atmosphere, and aluminum atoms in copper matrix get oxidized to
form alumina due to the reaction, 4Cu(Al) + 3O 2 = 4Cu + 2Al 2 O 3 . In addition,
Fig. 1 a TEM image showing the elongated grains of cold worked copper-alumina composite.
b HRTEM image close to [110] zone of copper showing the microtwins in copper matrix. The
corresponding FFT showing the twin related reflections is given as an inset. (Color figure online)
135
by x-ray diffraction (XRD) using a Rigaku 18 kW x-ray generator and a highresolution powder diffractometer utilizing Cu-Kα 1 . For TEM, samples were prepared
by initially polishing the disk samples mechanically and finally by thinning in an ion
mill with a gun voltage of 4 kV and a sputtering angle of 10°. Tecnai G
2 analytical
transmission electron microscope operating at 300 keV was used to characterize the
microstructure and dislocations. Furthermore, a JEOL 2200 analytical transmission
electron microscope operating at 200 keV was used to characterize the microstructure
and interfacial characteristics of the oxide particulates. To investigate the mechanical
behavior, micro and nano indentation hardness tests were performed to obtain hardness and elastic modulus of copper-alumina composite. For micro-hardness, Vickers
tip at 200 gm of load and dwell time of 15 s was used. To investigate mechanical
behavior, nano indentation hardness tests were performed with a Berkovich indenter
to obtain hardness values of the composites and commercially pure copper.
Results and Discussion
A bright-field TEM image (see Fig. 1a) shows the elongated grains of the copperalumina composite as a result of cold work. This increases the tensile and yield
strengths by introducing high density of dislocations. Furthermore, a very fine dispersion of oxide particles in the size range of 5–10 nm has been observed in the matrix.
These oxide particles in copper matrix originate from the internal oxidation process of
copper matrix at elevated temperatures. In this process, initially, the powder is heated
in a controlled atmosphere, and aluminum atoms in copper matrix get oxidized to
form alumina due to the reaction, 4Cu(Al) + 3O 2 = 4Cu + 2Al 2 O 3 . In addition,
Fig. 1 a TEM image showing the elongated grains of cold worked copper-alumina composite.
b HRTEM image close to [110] zone of copper showing the microtwins in copper matrix. The
corresponding FFT showing the twin related reflections is given as an inset. (Color figure online)