Electron Backscatter Diffraction Detector Research Articles

Characterization of a copper matrix composite reinforced with nano/submicron-sized boron fabricated via spark plasma sintering

The addition of various reinforcing phases can improve the mechanical properties of copper. This study investigates the enhancement of the mechanical properties of copper by adding boron, focusing on overcoming the challenges associated with the homogeneous distribution of submicron/nanoscale secondary phases in metal matrix composites. Employing a combination of mechanical alloying and spark plasma sintering, a copper-boron composite containing 3 wt% boron was prepared. Scanning electron microscopy equipped with an electron backscatter diffraction detector and energy-dispersive X-ray spectroscopy was utilized to characterize the structure of the sintered samples and mechanically alloyed powder. A two-phase structure containing nano/submicron-sized boron distributed uniformly in the copper matrix was formed in the sintered sample. Instrumented micro-indentation tests were performed to characterize the mechanical behavior of the samples. The sintered composite sample exhibits significantly higher hardness than the sintered copper. The enhanced mechanical performance of the composite is primarily attributed to grain boundary strengthening and microstructural refinement, where nano/submicron-sized boron particles prevent grain growth and refine the microstructure, enhancing hardness and strength. Additionally, dispersion strengthening from hard boron particles and the presence of a high density of twin boundaries within the copper matrix increase resistance to dislocation motion and deformation, and further improving the material's mechanical properties. On the other hand, the composite sample exhibits increased electrical resistivity due to the boron’s role as electron scattering centers. Overall, this study provides a valuable strategy for the design and optimization of advanced copper-based composites with tailored mechanical and electrical properties.

Friction stir processing of AA6061-T6/graphene nanocomposites: Unraveling the influence of tool geometry, rotation, and advancing speed on microstructure and mechanical properties

This research investigated the effect of tool geometry, rotation, and advancing speed on the microstructure and mechanical properties of aluminum AA6061-T6/graphene nanocomposites fabricated by friction stir processing (FSP) using three conical tools with the pin cone angles (PCAs) of 2, 2.5, and 3°. In the first step of the study, the process was performed with and without graphene nanoplatelets (GNPs) at different rotations (710, 1120, and 1400 rpm) and advancing speeds (80, 125, and 160 mm/min). The yield strength, tensile strength, and microhardness of all the samples were lower than those of the base metal. In the second step of the study, the heat input was controlled by reducing rotations (112, 180, and 280 rpm) and advancing speeds (31.5, 25, and 20 mm/min). The mechanical properties of processed samples were studied by tensile tests and microhardness measurements. Microstructural evolution in samples was analyzed by means of a field emission scanning electron microscope (FESEM) equipped with an X-ray energy dispersive spectrometer (EDS) and electron back-scattered diffraction (EBSD) detector. The results indicated that the mechanical properties were improved in the second step with the increase in the advance per revolution (APR) and the PCA. This was linked to the microstructure evolution in the processed samples affected by process parameters and regulated heat input. The effect of each input variable on the mechanical properties was evaluated by statistical analysis and was validated by analysis of variance (ANOVA). The optimal processing was attained by utilization of PCA, tool rotation, and advancing speed.

The Influence of Crystal Orientation and Thermal State of a Pure Cu on the Formation of Helium Blisters

The factors that influence the formation of helium blisters in copper were studied, including crystallographic grain orientation and thermomechanical conditions. Helium implantation experiments were conducted at 40 KeV with a dose of 5 × 1017 ions/cm2, and the samples were then subjected to post-implantation heat treatments at 450 °C for different holding times. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to analyze the samples, revealing that the degree of blistering erosion and its evolution with time varied with the crystallographic plane of the free surface in different ways in annealed and cold rolled copper. Out of the investigated states, rolled copper with a (111) free surface had superior helium blistering durability. This is explained by the consideration of the multivariable situation, including the role of dislocations and vacancies. For future plasma-facing component (PFC) candidate material, similar research should be conducted in order to find the optimal combination of material properties for helium blistering durability. In the case of Cu selection as a PFC, the two practical approaches to obtain the preferred (111) orientation are cold rolling and thin layer technologies.

Point-Contact Spectroscopy in Bulk Samples of Electron-Doped Cuprate Superconductors.

Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd2-xCexCuO4-δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with Ce content x = 0.15 showed the absence of spurious phases and randomly oriented grains, most of which had dimensions of approximately 220 µm2. The low-bias spectra in the tunneling regime, i.e., high-transparency interface, exhibited a gap feature at about ±5 meV and no zero-bias conductance, despite the random oriented grains investigated within our bulk samples, consistent with most of the literature data on oriented samples. High-bias conductance was also measured in order to obtain information on the properties of the barrier. A V-shape was observed in some cases, instead of the parabolic behavior expected for tunnel junctions.

Imaging Threading Dislocations and Surface Steps in Nitride Thin Films Using Electron Backscatter Diffraction.

Extended defects, like threading dislocations, are detrimental to the performance of optoelectronic devices. In the scanning electron microscope, dislocations are traditionally imaged using diodes to monitor changes in backscattered electron intensity as the electron beam is scanned over the sample, with the sample positioned so the electron beam is at, or close to the Bragg angle for a crystal plane/planes. Here, we use a pixelated detector instead of single diodes, specifically an electron backscatter diffraction (EBSD) detector. We present postprocessing techniques to extract images of dislocations and surface steps, for a nitride thin film, from measurements of backscattered electron intensities and intensity distributions in unprocessed EBSD patterns. In virtual diode (VD) imaging, the backscattered electron intensity is monitored for a selected segment of the unprocessed EBSD patterns. In center of mass (COM) imaging, the position of the center of the backscattered electron intensity distribution is monitored. Additionally, both methods can be combined (VDCOM). Using both VD and VDCOM, images of only threading dislocations, or dislocations and surface steps can be produced, with VDCOM images exhibiting better signal-to-noise. The applicability of VDCOM imaging is demonstrated across a range of nitride semiconductor thin films, with varying surface step and dislocation densities.

MT-CVD Ti(C,N,O) coatings controlled by CO: Microstructure evolution and its effect on the hardness

Incorporation of oxygen into Ti(C,N) coating by CO doping during moderate temperature chemical vapor deposition (MT-CVD) process is a promising strategy for enhancing the performance of cutting tools. In this work, Ti(C,N,O) coatings were prepared by MT-CVD in a hot-wall industrial-scale CVD reactor with increased CO volume fraction from 0 % to 8.0 % in the feed gas mixture. Microstructure evolution is revealed by high-resolution scanning electron microscopy, electron backscatter diffraction detector, and high-resolution transmission electron microscopy. Its effect on the hardness is investigated. The results show that as the CO fraction increases, the microstructure changes from columnar and large faceted grains to equilateral and nanoscale grains. An increasing density of plane defects including twins, especially Σ3 twin boundaries and stacking faults are identified in Ti(C,N,O) coatings with increasing CO fraction. The hardness of Ti(C,N,O) coatings increase from 26 GPa at 0 % CO to 34 GPa at 8.0 % CO, due to the grain refinement, solution strengthening, increased stacking faults, twins and {111} texture. A considerably lower rate of hardness increase is observed at CO fractions above 4.0 %, which is hypothesized to be related to grain boundary sliding, residual chlorine and excessive density stacking faults.

Hot Working of an Fe-25Al-1.5Ta Alloy Produced by Laser Powder Bed Fusion

In the present work, hot working was used as a post-processing method for Fe-25Al-1.5Ta (at.%) alloy built using laser powder bed fusion (LPBF) to refine the undesirable columnar microstructure with heterogeneous grain sizes and strong textures in the build direction. The hot deformation behavior and workability were investigated using constitutive modeling and the concept of processing maps. Uniaxial compression tests were conducted up to a true strain of 0.8 at 900 °C, 1000 °C, and 1100 °C with strain rates of 0.0013 s−1, 0.01 s−1, and 0.1 s−1. The constitutive equations were derived to describe the flow stress–strain behavior in relation to the Zener–Hollomon parameter. Processing maps based on a dynamic materials model were plotted to evaluate the hot workability and to determine the optimal processing window as well as the active deformation mechanisms. The microstructure of the deformed specimens was characterized by scanning electron microscopy equipped with an electron backscatter diffraction detector. The results indicated a high degree of hot workability of the LPBF builds without flow instabilities over the entire deformation range tested. The epitaxially elongated grains of the as-built alloys were significantly refined after deformation through dynamic softening processes, and the porosity was reduced due to compressive deformation. The current study revealed a well-suited parameter range of 1000–1080 °C/0.004–0.012 s−1 for the safe and efficient deformation of the LPBF-fabricated Fe-25Al-1.5Ta alloys. The effectiveness of the process combination of LPBF with subsequent hot forming could be verified with regard to microstructure refinement and porosity reduction.

An EBSD camera as a tool to characterise in-plane magnetisation vectors on Fe-Si (001) surface

Previous studies have shown that type-II magnetic-domain contrasts are caused by differences in the backscattering yields of magnetic domains of opposite magnetisation. Imaging the magnetic domains when the magnetisation vectors in the opposite-magnetisation domains are perpendicular to the tilt axis of the specimen has been considered difficult, because of the lack of change in the backscattering yields between the domains. An alternative way to obtain the type-II magnetic-domain contrasts is to utilise the difference in the exit angular distribution of the backscattered electrons from different magnetic domains. In this study, it is found that an electron backscatter diffraction (EBSD) camera can be used to obtain the type-II magnetic-domain contrasts caused by the above two mechanisms simultaneously. We verify this by distinguishing all four possible in-plane magnetisation vectors on a Fe–Si (001) surface without a sample rotation, using an EBSD detector as an array of electron detectors. The change in contrast between the magnetic domains, with respect to the location of a virtual electron detector, can provide information on the directions of the magnetisation vectors. A method to suppress the topographic contrast superimposed on the magnetic-domain contrast is also demonstrated.

Morphology and Structure of Brass–Invar Weld Interface after Explosive Welding

This paper presents the results of a study of the morphology and structure at the weld interface in a brass-Invar bimetal, which belongs to the class of so-called thermostatic bimetals, or thermobimetals. The structure of the brass-Invar weld interface was analyzed using optical microscopy and scanning electron microscopy (SEM), with the use of energy-dispersive X-ray (EDX) spectrometry and back-scattered electron diffraction (BSE) to identify the phases. The distribution of the crystallographic orientation of the grains at the weld interface was obtained using an e-Flash HR electron back-scatter diffraction (EBSD) detector and a forward-scatter detector (FSD). The results of the study indicated that the weld interface had the wavy structure typical of explosive welding. The wave crests and troughs showed the presence of melted zones consisting of a disordered Cu-Zn-Fe-Ni solid solution and undissolved Invar particles. The pattern quality map showed that the structure of brass and Invar after explosive welding consisted of grains that were strongly elongated towards the area of the highest intensive plastic flow. In addition, numerous deformation twins, dislocation accumulations and shear bands were observed. Thus, based on the results of this study, the mechanism of Cu-Zn-Fe-Ni structure formation can be proposed.

Microstructural Characteristics and Hardness Enhancement of Super Duplex Stainless Steel by Friction Stir Processing

In the present study, microstructural evolution and hardness of the friction stir processed (FSPed) SAF 2507 super duplex stainless steel fabricated at a rotational speed of 650 rpm and a traverse speed of 60 mm/min were investigated. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to study the microstructure of the stir zone. The grain sizes of austenite and ferrite in the FSPed 2507 were found to be smaller (0.75 and 0.96 μm) than those of the substrate (6.6 and 5.6 μm) attributed to the occurrence of continuous dynamic recrystallization (CDRX) in both phases. Higher degree of grain refinement and DRX were obtained at the advancing side of the FSPed specimens due to higher strain and temperature. A non-uniform hardness distribution was observed along the longitudinal direction of the SZ. The maximum hardness was obtained at the bottom (407 HV1).

Hot Deformation Behavior of Alloy AA7003 with Different Zn/Mg Ratios

The hot-deformation behavior of three medium-strength Al-Zn-Mg alloys with different Zn/Mg ratios was studied using isothermal-deformation compression tests; the true strain and true stress were recorded for constructing series-processing maps. A few constitutive equations describe the relationship between flow stress and hot-working parameters. The microstructures were characterized using an electron backscatter diffraction (EBSD) detector and transmission electron microscope (TEM). The results show that the optimized deformation parameters for ternary alloy AA7003 are within a temperature range of 653 K to 813 K and with strain rates lower than 0.3 S−1. The microstructures show that materials with a lower Zn/Mg ratio of 6.3 could lead to a problematic hot-deformation capability. Alloys with a higher Zn/Mg ratio of 10.8 exhibited better workability than lower Zn/Mg ratios. The Al3Zr dispersoids are effective in inhibiting the recrystallization for alloy AA7003, and the Zn/Mg ratios could potentially affect the drag force of the dispersoids.

Influence of laser powder bed fusion process parameters on the microstructure of solution heat-treated nickel-based superalloy Alloy 247LC

In this study, Alloy 247LC samples were built with different laser powder bed fusion (L-PBF) process parameters. The samples were then subjected to solution heat treatment at 1260 °C for 2 h. The grain size of all the samples increased significantly after the heat treatment. The relationship between the process parameters and grain size of the samples was investigated by performing a design of experiment analysis. The results indicated that the laser power was the most significant process parameter that influenced the grain height and aspect ratio. The laser power also significantly influenced the grain width. The as-built and as-built + heat-treated samples with high, medium, and low energy densities were characterized using a field emission gun scanning electron microscope equipped with an electron backscatter diffraction detector. The micrographs revealed that the cells present in the as-built samples disappeared after the heat treatment. Isolated cases of twinning were observed in the grains of the as-built + heat-treated samples. The disappearance of cells, increase in the grain size, and appearance of twins suggested that recrystallization occurred in the alloy after the heat treatment. The occurrence of recrystallization was confirmed by analyzing the grain orientation spread of the alloy, which was lower and more predominantly <1° in the as-built + heat-treated conditions than in the as-built conditions. The microhardness of the as-built + heat-treated samples were high which was plausible because γ’ precipitates were observed in the samples. However, the L-PBF process parameters had a very low correlation with the microhardness of the as-built + heat-treated samples.

A study on the creep behavior of alloy 709 using in-situ scanning electron microscopy

In this research, an experimental evaluation of creep properties of Alloy 709 in the temperature range of 750–850 °C was undertaken. Alloy 709 is a novel austenitic stainless steel with 20% Cr and 25% Ni by wt% that was developed for application in structural components of nuclear power plants. Creep rupture tests were conducted in an in-situ heating-loading and Scanning Electron Microscope (SEM) unit equipped with Electron Backscatter Diffraction (EBSD) detector and Energy Dispersive Spectroscopy (EDS). “Real-time” creep damage mechanisms of Alloy 709 at various stresses and temperatures using a flat, un-notched sample with continuously reducing cross-section is studied so that the failure and maximum creep damage occurred at the center of the sample where the in-situ SEM imaging could be focused. Accelerated creep tests at temperatures and stresses above service conditions were performed by employing multiple blocks of constant loads where the loads were increased once the sample attained constant creep rate, indicating a secondary creep regime. This technique ensures multiple data points can be obtained from the same test, saves the time required for an otherwise long-term creep test and usage of SEM. Coincident Site Lattice (CSL) boundary maps were collected as control maps before testing, and the grain boundaries were observed during the creep test to understand the effect of grain boundary character on the creep damage mechanism. Void growth, grain boundary separation, and sliding were found to be the main creep mechanisms whose rate is dependent on stress and temperature. Failure mechanisms studied on the fracture surface using SEM fractography were correlated to the sample surface observations to create complementary information to better understand the underline creep mechanism of Alloy 709.

Study on the SCC behavior induced by creep cavities on scratched surface of Alloy 690TT in high temperature water

SCC behavior induced by creep of Alloy 690TT in high temperature water was investigated in this study using scanning electron microscopy (SEM) with energy dispersive X-ray (EDS) detector and electron back-scattered diffraction (EBSD) detector. The results showed that the creep cavities could be formed in the stress concentration zones on the interface between the intergranular carbides and matrix. The distribution density of creep cavities was related to the strain level. The cavities mainly distributed on the grain boundaries close to the applied load direction in the high strain zones underneath the scratches. The creep cavities tended to form near the intergranular carbides distributed in a semi-continuous line along the grain boundaries, which was beneficial to the SCC propagation. On the contrary, the local cellular carbides might not be conducive to the formation of creep cavities and inhibited the growth of SCC cracks. In the high strain zone underneath the scratch, the SCC cracks mainly propagated along or close to the direction of applied load.

Comparing the effect of continuous and pulsed current in the GTAW process of AISI 316L stainless steel welded joint: microstructural evolution, phase equilibrium, mechanical properties and fracture mode

In this paper, the effect of continuous and pulsed current in the gas tungsten arc welding (GTAW) on the various properties of an AISI 316L stainless steel joints was investigated. 316L austenitic stainless steel sheets with a thickness of 10 mm were used together with ER309L filler. The sheets were welded together by the GTAW technique in two modes of continuous and pulsed currents. Microstructural characterization and phase equilibria were done using optical microscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) equipped with electron backscatter diffraction (EBSD) detector, techniques. Charpy impact, uniaxial tensile, and microhardness tests were used to investigate the effect of the type of the welding current on mechanical properties of the joints. The fracture surfaces were evaluated by FE-SEM after tensile and Charpy impact tests. Results showed that the weld metal (WM) microstructure is austenitic-ferritic (AF). It was also consisted of columnar and coaxial structures, in a way that varying the welding current from continuous to the pulsed mode changed the morphology of the grains from elongated columnar to a fine coaxial morphology. In addition, such a change in the welding current reduced the size of the grains in the WM, and the width of the unmixed zone (UMZ) as well. XRD analysis showed that the predominant phase and the preferred crystal plane of the WM are austenite, and (111), respectively. Both joints were broken from the base metal (BM) during the tensile test. Also, the above change of the welding current mode increased hardness and fracture toughness of the WM. Finally, fractography of the joints indicated that both joints experienced a completely ductile fracture.

Effect of a trace amount addition of CuO on aluminum sheet processed by accumulative roll bonding with the common roots and rapid annealing

In this paper, the Al–CuO nanocomposite is prepared by the addition of 0.5 vol.% CuO and up to six accumulative roll bonding (ARB) process cycles. Furthermore, the pure aluminum sheets were processed by the ARB. A scanning electron microscope, equipped with an electron backscattered diffraction detector, was used to assess the microstructure. Also, to investigate the effect of rapid annealing on the ARB-ed sheets, aluminum, and Al–CuO composite were subjected to ARB with rapid annealing between ARB cycles. Tensile testing and microhardness testing, together with fracture surface analyses, were employed to evaluate the ARB processed specimens. The texture analysis from the ARB processed specimens demonstrated that the texture components close to S{123} <634>, Cube {001} <100>, and Brass {011} <211> were developed. Microstructure characterization results demonstrated that the mean grain size of less than 500 nm is obtainable after the 6-cycle of the ARB. As well as, the ultimate tensile strength and microhardness substantially increased by 2.5 and two times, respectively. Al–CuO composite showed higher resistance to rapid annealing. The higher resistance of the composite to rapid annealing between ARB cycles was proven in tensile strength, mean grain size, and microhardness.

Role of crystallographic textures on the growth of CuO nanowires via thermal oxidation

To investigate the influence of crystallographic textures on the growth of CuO nanowires, nanocrystalline coppers with distinct textures were fabricated using an electrodeposition. Thermogravimetric analysis, x-ray diffraction analysis, and scanning electron microscopy equipped with an electron backscattered diffraction detector were employed to investigate the growth of CuO nanowires at 200 °C and 300 °C. While a high number-density of nanowires was clearly observed in the (100) and (101)-textured coppers, it was not the case for the copper with strong (111) texture, indicating that the growth of CuO nanowires via a low-temperature thermal oxidation can be achieved by tailoring the texture. Data availabilityThe raw and processed data required to reproduce these findings are available to download from [https://data.mendeley.com/datasets/6zjnhgk7vc/draft?a=8057336c-389a-451d-95e0–756b5e93cb99].

High Strain Rate Properties of Various Forms of Ti6Al4V(ELI) Produced by Direct Metal Laser Sintering

For analysis of engineering structural materials to withstand harsh environmental conditions, accurate knowledge of properties such as flow stress and failure over conditions of high strain rate and temperature plays an essential role. Such properties of additively manufactured Ti6Al4V(ELI) are not adequately studied. This paper documents an investigation of the high strain rate and temperature properties of different forms of heat-treated Ti6Al4V(ELI) samples produced by the direct metal laser sintering (DMLS). The microstructure and texture of the heat-treated samples were analysed using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction detector for electron backscatter diffraction (EBSD) analysis. The split Hopkinson pressure bar (SHPB) equipment was used to carry out tests at strain rates of 750, 1500 and 2450 s−1, and temperatures of 25, 200 and 500 °C. The heat-treated samples of DMLS Ti6Al4V(ELI) alloys tested here were found to be sensitive to strain rate and temperature. At most strain rates and temperatures, the samples with finer microstructure exhibited higher dynamic strength and lower strain, while the dynamic strength and strain were lower and higher, respectively, for samples with coarse microstructure. The cut surfaces of the samples tested were characterised by a network of well-formed adiabatic shear bands (ASBs) with cracks propagating along them. The thickness of these ASBs varied with the strain rate, temperature, and various alloy forms.

Enhanced Degradability of Mg-2Gd Alloy by Alloying Cu

To obtain alloys with both high degradability and plasticity used in the petroleum industry, 0.25, 0.5, 0.75 and 1.0 wt.% Cu were added into Mg-2Gd alloy. With Cu addition, finer grain size, precipitation of Mg2Cu, and variations of crystal orientation were observed. Regardless of the good mechanical properties gained by alloying Cu, the degradation rate was obviously increased in this study. The corrosion rate and I corr of Mg-2Gd were 13.0 ± 0.1 mm·y−1 and 1.04 × 10−4 A·cm−2, respectively, while those value of Mg-2Gd-1Cu increased to 226.4 ± 6.1 mm·y−1 and 3.42 × 10−4 A·cm−2, respectively. We confirmed by scanning Kelvin probe force microscopy and scanning electron microscope with electron backscatter diffraction detector that profuse second phases (mainly Mg2Cu), refinement of grain size, and weakened rare earth texture contributed to the lower corrosion resistance.

Effects of oxygen content on Charpy impact properties and crack resistance of α titanium alloys

Charpy impact properties and crack resistance of commercial pure (CP) Ti and Ti–6Al alloy with different oxygen contents were systematically investigated by using the instrumented Charpy impact testing machine. The scanning electron microscope (SEM) equipped with electron backscatter diffraction (EBSD) detector and transmission electron microscope were employed to detect the deformation mechanisms. The experimental results showed that decreasing the oxygen content significantly improved the impact toughness of CP Ti and Ti–6Al alloy. Furthermore, decreasing the oxygen content simultaneously strengthened the resistance to crack initiation and propagation of CP Ti while only improved the resistance to crack propagation of Ti–6Al alloy. EBSD analysis demonstrated the significant effects of oxygen content on dislocation activities and deformation twinning behaviors in CP Ti and Ti–6Al. Decreasing the oxygen content significantly increased the dislocation activities and deformation twinning behaviors in CP Ti and Ti–6Al alloy which were mainly responsible for the improved impact properties and the strong crack resistance of CP Ti and Ti–6Al alloy. A mathematical model was introduced for the first time to uncover the interactions between oxygen atoms and dislocation as well as the deformation twinning on the view of valence electron by employing the Yu Rui-huang electron theory. By conducting the systematically experimental and theoretical investigations, we are aiming to provide deep insights into the relationships between interstitial oxygen and impact toughness as well as the crack resistance of titanium alloys and promote the production of titanium alloys with excellent impact properties.