Jui Chao Kuo

Effect of microscopic parameters on EBSD spatial resolution

In this study, a quantitative approach is proposed to understand the effect of the accelerating voltage and the probe current on the physical resolution of EBSD. The accelerating voltage was varied from 5 to 30kV and probe currents of 1, 10, and 40nA were selected. The lateral, longitudinal, and depth resolutions at 10kV and 1nA were 34.5, 44.7, and 46nm for copper, respectively. When the accelerating voltage was in the range of 5-20kV, the ratio of the longitudinal to the lateral resolution was below the theoretical ratio of 2.9. Considering the channeling effect, the best physical depth resolution of 38nm was achieved at 5kV and 10nA. The physical depth resolution in an EBSD measurement is much larger due to the channel effect than that obtained without considering this effect.

Effect of pre-oxidation on increasing resistance of Fe–Al–Ni–Cr–Co–Mn high entropy alloys to molten Al attack

Abstract The corrosion behaviours of two high entropy alloys (HEAs, namely Fe–Al–Ni–Cr–Co and Fe–Al–Ni–Cr–Co–Mn) in molten Al, each with and without pre-oxidation treatment, were investigated. Both bare alloys lost their thickness owing to dissolution, and various intermetallic compounds formed on their substrate surfaces during immersion in molten Al. Pre-oxidation treatment gave rise to the formation of an effective oxide barrier on each alloy surface against molten Al attack. The characteristics of pre-formed oxides in resisting molten Al attack were examined using electron backscatter diffraction (EBSD) analysis.

Characterization of Laves phase in Crofer 22 H stainless steel.

This study investigated the effect of annealing temperature on the precipitation behavior of Crofer(®) 22 H at 600°C, 700°C, and 800°C. The grain size distribution, precipitate phase identification, and microstructure were analyzed using electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS). The morphology of Laves phase (Fe,Cr,Si)(2)(Nb,W) precipitates having the Cr(2)Nb structure changed from strip-like to needle-shaped as the annealing temperature was increased. The precipitates of the Laves phase also shifted from the grain boundaries to the grain interiors when the temperature was increased. However, the average grain size (150 μm) of the ferritic matrix did not significantly change at 600°C, 700°C, and 800°C for 10 h.

Effect of Plating Current Density and Frequency on the Crystallographic Texture of Electrodeposited Copper

For interconnect materials in the microelectronic technology copper has replaced aluminum due to its lower resistivity, higher thermal conductivity and better electromigration resistance. Recently, it was found that nanotwinned copper exhibits ultra high yield strength, ductility and electrical conductivity. Therefore, in this study the effect of plating current density and frequency were investigated on the crystallographic texture of Cu electrodeposited to understand the twin character. Electron backscatter diffraction (EBSD) was used for characterizing the preferred orientation, grain size distribution, and grain boundary character distribution. Three kinds of <110>, <111> and <112> textures were found to be related with the electrodeposited parameters of current density and frequency. Here we will discuss the relationship between the preferred orientation and the electrodeposited parameters.

The effect of atomic mass on the physical spatial resolution in EBSD

In this study, bicrystals of silver (Ag) and aluminum (Al) were used to investigate the physical spatial resolution of the electron backscatter diffraction system combining a digital image correlation method. Furthermore, the effect of the accelerating voltage and probe current was investigated on the physical spatial resolution of the lateral and longitudinal resolutions for Ag and Al, respectively. The lateral and longitudinal resolutions show high dependency on the accelerating voltage for a low atomic mass material of Al, In addition, these are almost independent of the accelerating voltage for a high atomic mass material of Ag. Moreover, the probe current does not play any role on both the lateral and longitudinal resolutions. The best lateral resolutions for Al and Ag are 40.5 and 12.1 nm at 10 kV and 1 nA, respectively. The best longitudinal resolutions of 23.2 and 80 nm were obtained at 10 kV and 1 nA for Al and Ag, respectively.

EBSD and electron channeling study of anomalous slip in oligocrystals of high chromium ferritic stainless steel

In the present study, electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) techniques were applied to investigate the deformation pattern of coarse ferrite grains after being subjected to 3%, 6%, and 10% tensile deformation. Oligocrystals of Crofer® 22H ferritic steel were obtained as experimental material at 1075°C for 22min annealing. Using kernel average misorientation (KAM) mapping obtained from EBSD, possible slip planes are (110), (101), (12-1) and (32-1) in grain A; (0-11), (-101), (-112), (1-21) in grain B; and (0-11), (1-21) and (11-2) in grain C. Combining ECCI and EBSD techniques enables us to identify two a0[11¯1]/2 edge dislocations that occur on the (110)[1-11] and (32-1)[1-11] slip systems for grain A, thereby breaking down Schmids law.

Effects of accelerating voltage and specimen thickness on the spatial resolution of transmission electron backscatter diffraction in Cu

A quantitative approach was proposed to determine the spatial resolution of transmission electron backscatter diffraction (t-EBSD) and to understand the limits of spatial resolution of t-EBSD. In this approach, Cu bicrystals and digital image correlation were employed. The effects of accelerating voltage and specimen thickness on the spatial resolution of t-EBSD were also investigated. t-EBSD specimens with 8μm×10μm dimensions and different thicknesses were prepared using focused ion beam milling. The optimized quality of Kikuchi pattern was achieved at a working distance of 12mm and a tilting angle of 20°. The optimum depth resolution of 34.4nm was observed in the lower surface of a 100nm thick sample at 25kV. Thus, the penetration depth from the upper surface is 65.6nm. The optimum lateral and longitudinal resolutions obtained from a 100nm thick sample at 30kV are 25.2 and 43.4nm, respectively. The spatial resolution of t-EBSD can be enhanced by increasing the accelerating voltage and decreasing the sample thickness.

Using the Simplified 3D DIC Method to Measure the Deformation of 3D Surface

In recent years, 2D digital image correlation method (DIC) has been widely used in the measurement of plane strain. However, out-of-plane displacement could be induced during the loading and it would affect the measurement accuracy. Thus, a 3D measurement is necessary. This study utilizes a simplified 3D DIC to measure the geometry of an object before and after deformation. Then the finite element concept is involved to determine the strain after deformation. A flat plate specimen with in-plane and out-of-plane displacement is observed. Both 2D and 3D DIC are used to analyze the strain. The results show that using 3D DIC to measure strain is feasible and with a very good accuracy.

Effects of electromigration on grain rotation behavior of SnAg solders

The requirement for smaller devices but with much greater performance leads to a boost in current density and damage caused by electromigration. Recently, some researches show that the grain orientation changes durin

Effect of prior deformation on microstructural development and Laves phase precipitation in high-chromium stainless steel

This study investigated the influence of deformation on precipitation behaviour and microstructure change during annealing. Here, the prior deformation of high‐chromium stainless steel was tensile deformation of 3%, 6% and 10%, and the specimens were then annealed at 700˚C for 10 h. The specimens were subsequently analyzed using backscattered electron image and electron backscattering diffraction measurements with SEM. Compared with the deformation microstructure, the grains revealed no preferred orientation. The precipitates of TiN and NbC were formed homogenously in the grain interior and at grain boundaries after annealing. Fine Laves phase precipitates were observed in grains and along subgrain boundaries as the deformation increased. Furthermore, the volume fraction of Laves phase increased, but the average particle diameter of precipitate was reduced as the deformation increased.