Pips 691

The composition of Al 7075 alloy was analyzed using an Inductively Coupled Plasma-Optical Emission Spectr (Prodigy 7). The median particles diameters were measured using a Malvern laser particle size analyzer (Mastersizer 2000). Samples for TEM studies were prepared by mechanically grinding the bulk material to a thickness of ~80 µm, then dimpling in the center to a thickness of approximately 15 µm. Further thinning to a thickness of electron transparency was carried out using an Ion Milling (Gatan PIPS 691) system at liquid nitrogen temperatures. The microstructure of the samples was characterized by transmission electron microscopy (JEOL2800, JEOL2500 and FEI CM20).
The number density of GP zones per unit area was estimated by counting the numbers of GP zones in at least ten STEM photographs of each zone using an image analysis tool, Image J^®. The area for each photograph is approximately 160 nm × 160 nm.

The microstructural characterization has been conducted using TEM (FEI Tecnai G2 F20) as well as aberration-corrected STEM (FEI Titan G2 80–200), both operated at 200 kV. STEM HAADF images were taken using an annular detector with a collection range of 60–160 mrad. Cross-sectional samples for TEM characterization were prepared by a standard grinding and thinning and a final ion-milling (Gatan PIPS 691 precision ion polishing system). The X-ray diffraction was carried out with a Panalytical Empyrean high-resolution X-ray diffractometer using Cu-Kα radiation (λ=1.5405 Å). To measure transport characteristics with temperature variation from 20 to 550 °C, we used a probe station equipped with a hot plate. The ac and dc measurements were performed by an HP 4294A Precision Impedance Analyser and Keithley 2,440 sourcemeter, respectively. For all transport measurements, we grounded the Nb:STO substrate and applied the voltage to the Pt electrodes.

Microstructure
analyses were performed on thermally etched (1150 °C in air for
15 min) cross sections using a scanning electron microscope (SEM;
Thermo Fisher Quanta 650 ESEM, Massachusetts, USA) with a thermionic
electron source.
Samples for scanning transmission electron
microscopy (STEM) were prepared by cutting a 3 mm disk from the ceramic
pellet, mechanical thinning to ∼100 μm, dimpling to ∼20
μm in the disc center (Dimple grinder, Gatan Inc., Warrendale),
and finally, ion milling to perforation using 3.8 keV Ar ions at an
angle of 8° from both sides (PIPS 691, Gatan Inc., Pleasanton,
USA). After perforation, the energy was gradually lowered, finally
to 500 eV for 5 min to minimize the thickness of the amorphous surface
layer. STEM analyses were performed using a probe-corrected atomic-resolution
microscope (JEOL ARM200 CF, Jeol Ltd., Tokyo, Japan) operated at 200
kV and equipped with a high-angle annular dark-field (HAADF) detector
with inner and outer semiangles of 68 and 180 mrad, respectively.
EELS spectra were acquired using a Gatan DualEELS Quantum ER spectrometer.
Samples for STEM analyses were coated with 2 nm of amorphous carbon
(PECS 682, Gatan Inc., Pleasanton, USA) to prevent charging under
the electron beam.

Electron backscattered diffraction (EBSD) mapping using a step size of 1 μm was performed on a FEI Nova 400 SEM equipped with a HKL Channel 5 system. The precipitates were examined by transmission electron microscopy (TEM) on a FEI-F20 TEM. Thin foils for TEM observation were prepared by mechanical grinding and subsequent ion beam thinning (Gatan PIPS 691).

As-extruded Zn-0.8Li alloys were cut into 1 mm thickness disk followed by grounding and polishing with 0.25 µm diamond slurry. Polished samples were etched with 4% HNO₃/alcohol solution for 5-10 s and pictured by a scanning electron microscopy (Hitachi S-4800, Japan). An X-ray diffractometer (XRD, Rigaku DMAX 2400, Japan) was used to examine the intermetallic phases with scanning range from 10° to 90° at a scan rate of 2° min⁻¹ and step of 0.02°. Polished samples were further processed into 60 µm thickness, followed by punching into 3 mm diameter disks, and ion-beam milling using Gatan PIPS 691 with 10 KeV at −25 °C to −30 °C. Samples were plasma cleaned by Gatan SOLARUS 950 before visualized under a high-resolution high-angle annular dark-field mode (HAADF) at 300 kV using a scanning transmission electron microscopy (FEI Titan G2 60–300 ChemiSTEM).