Electron Backscatter Diffractometry Research Articles

Surface Integrity of Inconel 738LC Parts Manufactured by Selective Laser Melting Followed by High-speed Milling

This study is concerned with the surface integrity of Inconel 738LC parts manufactured by selective laser melting (SLM) followed by high-speed milling (HSM). In the investigation process of surface integrity, the study employs ultra-depth three-dimensional microscopy, laser scanning confocal microscopy, scanning electron microscopy, electron backscatter diffractometry, and energy dispersive spectroscopy to characterize the evolution of material microstructure, work hardening, residual stress coupling, and anisotropic effect of the building direction on surface integrity of the samples. The results show that SLM/HSM hybrid manufacturing can be an effective method to obtain better surface quality with a thinner machining metamorphic layer. High-speed machining is adopted to reduce cutting force and suppress machining heat, which is an effective way to produce better surface mechanical properties during the SLM/HSM hybrid manufacturing process. In general, high-speed milling of the SLM-built Inconel 738LC samples offers better surface integrity, compared to simplex additive manufacturing or casting.

Microstructure, Flexural Strength, and Fracture Toughness Comparison between CAD/CAM Milled and 3D-Printed Zirconia Ceramics

The present study comprehensively compared the microstructure, flexural strength, and fracture toughness of zirconia ceramics prepared via two different methods, subtractive milling (SM) and stereolithography (SLA). Disc- or rectangular-shaped zirconia specimens (Prettau (SM) and 3DMix Zirconia (SLA)) were prepared following each manufacturer’s instructions and polished. The microstructures of the two different zirconia specimens were studied by scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, and electron backscattered diffractometry. The flexural strength and fracture toughness based on the indentation fracture method were measured for the two different zirconia ceramics. A greater number of small pores and smaller grains were found in the SLA specimen than in the SM specimen. The crystal structure and microstructure analysis revealed that both ceramics had a similar phase composition to each other. No significant differences in flexural strength (p = 0.242) or fracture toughness (p = 0.101) were detected between the two ceramics. The mean flexural strength of the SLA-fabricated zirconia as well as the SM zirconia satisfied the class 5 criteria (>800 MPa) in the ISO 6872 standard.

Effects of trace Ag on precipitation behavior and mechanical properties of extruded Mg−Gd−Y−Zr alloys

The effects of trace Ag element on the precipitation behaviors and mechanical properties of the Mg−7.5Gd− 1.5Y−0.4Zr (wt.%) alloy by means of tensile test, X-ray diffractometry, scanning electron microscopy, electron backscattered diffractometry, and scanning transmission electron microscopy. There is an unusual texture (〈0001〉//extrusion direction) in the extruded Mg−Gd−Y−Zr alloys containing 0.5 wt.% Ag. During the aging periods at 225 °C, the addition of the trace Ag does not form new precipitates, just accelerates aging kinetics, and refines β′ precipitates, thereby increasing the number density of the β′ precipitates by Ag-clusters. Moreover, the Mg−Gd−Y−Zr alloy containing 0.5 wt.% Ag shows the most excellent synergy of strength and plasticity (408 MPa of ultimate tensile strength, 265 MPa of yield strength, and 12.9% of elongation to failure) after peak-aging.

Hornera currieae n. sp. (Cyclostomatida: Horneridae): a new bathyal cyclostome bryozoan with reproductively induced skeletal plasticity

Here we describe a new hornerid, Hornera currieae n. sp. (Bryozoa: Cyclostomatida) from bathyal depths across the New Zealand region. Colonies are irregular, finely branched fans attaining ~40 mm or more in height. Key characters include: (1) thick, semi-hyaline porcellanous skeleton; (2) loss or reduction of nervi (longitudinal striae) away from growing tips; (3) sparse, threadlike cancelli; and (4) small (6187 m), widely spaced autozooidal apertures. Diagnostic hornerid traits possessed by H. currieae n. sp. include vertical ancestrular tube, periancestrular budding of daughter zooids, and skeletal ultrastructure dominated by hexagonal semi-nacre grading to pseudofoliated fabric. The abfrontal incubation chamber develops from a cryptic tube arising from the frontally positioned aperture of the fertile zooid. We used SEM, micro-CT and electron backscatter diffractometry (EBSD) to investigate the ultrastructure and internal architecture of H. currieae n. sp. EBSD reveals that crystalline c-axes of laminated crystallites are perpendicular to skeletal walls. Threadlike cancelli, which traverse secondary calcification, connect autozooidal chambers to the colony-wide hypostegal cavity. Micro-CT reveals that abfrontal cancelli usually bend proximally towards the base, but turn distally towards reproductively active regions of the colony in synchrony with gonozooid development. The zone of affected cancelli extends for 47 branch internodes below the gonozooid. We assessed whether skeletal ultrastructure was similarly affected, but neither cancellus direction, nor gonozooid proximity, were predictive of the crystallite imbrication direction. We hypothesise that (1) hornerid cancelli are active conduits for colonial metabolite transport and (2) that changes in gradients of metabolites and/or reproductive morphogens within the hypostegal cavity affect cancellus morphogenesis. Potentially, H. currieae n. sp. skeletons may preserve a record of intra-colony metabolite translocation dynamics over time.

Annealing hardening and deformation behavior of layered gradient Zr–Ti composite

To investigate potential strengthening approaches, multi-layered zirconium–titanium (Zr–Ti) composites were fabricated by hot-rolling bonding and annealing. The microstructures of these composites were characterized using scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS) and electron backscatter diffractometry (EBSD). Their mechanical properties were evaluated by uniaxial tension and compression measurements. It was found that the fabricated Zr–Ti composites are composed of alternating Zr/diffusion/Ti layers, and chemical compositions of Zr and Ti showed a gradient distribution in the diffusion layer. Compared with as-rolled samples, annealing can strengthen the layered gradient Zr–Ti composite, and this is mainly caused by solid-solution strengthening and microstructure refinement-induced strengthening. Compared with the raw materials, a synergistic improvement of strength and ductility is achieved in the Zr–Ti composite as a result of the layered gradient microstructure. Tension–compression asymmetry is observed in the Zr–Ti composites, which may be attributed to twinning and microvoids induced by unbalanced diffusion.

Microstructural characterizations and wear and corrosion behaviors of laser-nitrided NAK80 mold steel

Abstract The effects of laser nitriding on the microstructural evolution and wear and corrosion behaviors of the NAK80 mold steel (AISI P21) were investigated. A high-power diode laser with a laser energy density of 1125 J/mm2 was employed for laser nitriding of NAK80. To examine the microstructure of laser-nitrided NAK80, diverse characterization methods such as scanning electron microscopy with electron backscatter diffractometry, high-resolution transmission electron microscopy with electron energy loss spectrometry, and atom probe tomography were utilized. These analyses revealed that the laser-nitrided region consisted of rod-like aluminum nitride (AlN) precipitates with various nitrides and carbides in the martensite matrix, resulting in the surface hardening of NAK80 from 409 to 536 HV. As a result, the laser-nitrided NAK80 exhibited an enhancement in the wear resistance in comparison to that of the base metal in the fretting test. The wear loss of laser-nitrided NAK80 was reduced by 33.4% compared to that of the base metal after 40,000 fretting cycles. However, a deterioration in the corrosion resistance was observed for the laser-nitrided NAK80 compared to the base metal. It may be associated with the elemental segregation in the vicinity of the AlN precipitates, which was observed in the atom-probe tomography.

The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods.

This work reports the effects of Microstructural changes due to the secondary phases, in particular sigma (σ), on the mechanical properties and electrochemical behavior of thermally aged duplex stainless steel (DSS). Structural, morphological, mechanical, and electrochemical characterizations were performed. Sigma phase content increased with increasing aging treatment time. It had a net-like shape, as observed by electron backscatter diffractometry (EBSD). Its presence directly damaged mechanical properties. The corrosion assessment included electrochemical impedance spectroscopy (EIS) in 1 M NaCl solution at temperatures of 25, 40, and 65 °C. EIS results demonstrate that an increase in the σ phase content decreased the corrosion resistance (21.1–0.8, 3.5–0.3, and 3.1–0.2 kΩ cm2 at 25, 40, and 60 °C, respectively).

Microstructural and mechanical properties of Ti-Mo alloys designed by the cluster plus glue atom model for biomedical application

β-type titanium alloys are acquiring research interest in orthopaedic applications because of their exceptional properties such as moderate strength, good biocompatibility and corrosion resistance, high ductility and low elastic modulus. The study aims at designing a series of binary Ti-Mo alloys (Ti-8.71 Mo, Ti-10.02 Mo, Ti-11.78 Mo and Ti-15.05 Mo (wt%)) using the cluster plus glue atom model to design the compositions. The prediction methods such as the molybdenum equivalence, the average electron ratio and the d-electron methods were used to predict the stability of the β phase. Microstructural evolution and phases of the designed alloys were characterized using the optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffractometry (EBSD) and X-ray diffractometry (XRD), while the microhardness and tensile properties were measured using the Vickers hardness tester and tensile testing machine. The microstructure of the cast Ti-Mo alloys comprised primarily the β phase and secondary orthorhombic martensitic α″ and athermal omega (ω) phases. Their elastic moduli (96.8–70.5 GPa) decreased with the amount of Ti in the glue side and were found to be lower than the commercially available 316 L stainless steel, Co-Cr and Ti6Al4V alloys. The microhardness values of the as-cast Ti-Mo alloys decreased as the amount of Ti in the glue side decreased in the cluster formula. The tensile strength of the as-cast alloys ranges from 796.76 to 593.48 MPa with Ti-8.71 wt% Mo alloy showing the highest tensile strength owing to the amount of Ti in the glue side. The yield strength of all the designed alloys decreased as the amount of Ti atoms placed in the glue side decreased. The elongation at fracture ranged between 0.28 and 0.71%, indicating that all the designed alloys fractured in a brittle manner. The elastic admissible strain of the designed alloys (Ti-15.05 wt% Mo) was significantly higher than the conventional orthopaedic implant materials (CP-Ti, Ti6Al4V) indicating that this study is promising for the development of excellent biomedical materials.

Investigation of the microstructure evolution of alpha uranium after in pile transient

This work describes the microstructural evolution of textured alpha uranium (α-U) specimens under different reactor transients achieving very low burn-up. The understanding of the behavior of this single phase will provide important information to further the material knowledge of metallic fuels (e.g. U-Pu-Zr, U-10Zr). Such alloys are of interest for their application in advanced reactor concepts. In metallic fuels α-U is, indeed, a relevant phase. Moreover, data on fuel behavior during early-stage irradiation are generally lacking and are important to validate and develop modelling and simulation tools. Characterization of grain boundaries, texture evolution, and phase transformation were obtained through scanning electron microscopy coupled with electron backscattered diffractometry and transmission electron microscopy .The data obtained indicates that phase transformation and microstructural change (e.g. recrystallization/grain growth) can occur during rapid transient even at low burn up. It is likely that the residual strain in the as-fabricated α-U specimens and the thermal strain introduced by reactor transients played an important role in the recrystallization of the α-U phase, as well as retaining the β-U phase at room temperature.

Evolution of microstructure and texture for an Al-0.4 Er alloy during accumulative roll bonding

Accumulative roll bonding (ARB) (comprising repetitive cycles of rolling) is highly attractive for the production of metal sheets with an ultrafine grained microstructure. The evolution of the microstructure and texture was investigated using optical microscopy, transmission electron microscopy and electron backscattered diffractometry during four cycles of ARB applied to an Al-0.4 Er alloy. Dynamicly recrystallized grains and deformed grains coexisted after the initial ARB cycle. The Er restricted abnormal grain growth, and facilitated the formation of a finer microstructure. Increasing number of ARB cycles caused a smaller grain size and a greater fraction of high angle grain boundaries. The mechanism was: (i) ARB caused a more uniform distribution of shear strain and a more remarkable texture evolution, and (ii) Er inhibited the texture intensity, and improved the random texture component.

Flow stress and dynamic recrystallization behavior of Al-9Mg-1.1Li-0.5Mn alloy during hot compression process

Abstract The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500 machine over deformation temperature range of 300-450 °C and strain rate of 0.01-10 s−1. The microstructural evolution of the alloy during the hot compression process was characterized by transmission electron microscopy (TEM) and electron back scatter diffractometry (EBSD). The results show that the flow stress behavior and microstructural evolution are sensitive to deformation parameters. The peak stress level, steady flow stress, dislocation density and amount of substructures of the alloy increase with decreasing deformation temperature and increasing strain rate. Conversely, the high angle grain boundary area increases, the grain boundary is in serrated shape and the dynamic recrystallization in the alloy occurs. The microstructure of the alloy is fibrous-like and the main softening mechanism is dynamic recovery during steady deformation state. The flow stress behavior can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of 184.2538 kJ/mol. The constitutive equation and the hot processing map were established. The hot processing map exhibits that the optimum processing conditions for Al-9Mg-1.1Li-0.5Mn alloy are in deformation temperature range from 380 to 450 °C and strain rate range from 0.01 to 0.1 s−1.

Microstructure and textural evolution during cold rolling and annealing of commercially pure titanium sheet

Abstract The effects of cold rolling and annealing on the microstructure and textural evolution of a commercially pure titanium (CP-Ti) sheet were investigated. Electron backscatter diffractometry demonstrates that the deformation during rolling is accommodated by twinning and slip. Additionally, twinning is the dominant deformation mechanism when the cold rolling reduction is less than 40%. During rolling, { 11 2 ¯ 2 } 〈 11 2 ¯ 3 ¯ 〉 contraction twinning (CT) and { 10 1 ¯ 2 } 〈 10 1 ¯ 1 〉 extension twinning (ET) are activated. And, the intensity of the (0002) pole along the ND gradually increases with increasing deformation. During annealing, the fraction of low angle grain boundaries (LAGBs) and the intensity of the (0002) pole along the ND gradually decrease slightly with increasing annealing time, while twinning lamellae disappear rapidly. When the annealing time reaches 60 min, 20% cold-rolled sheet recrystallizes almost completely.

Microstructure evolution and recrystallization behavior of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy during annealing

Abstract The effects of cold-rolling reduction, annealing temperature, and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test, scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffractometry (EBSD). The results show that the rate of the recrystallization increased with increasing annealing temperature and rolling reduction. Recrystallized grains nucleated preferentially at sites with high density dislocation and deformation stored energy and then grew into integral grains. Recrystallization texture changed from 〈 10 1 ¯ 0 〉 //RD to 〈 11 2 ¯ 0 〉 //RD. The grain orientation changed from random orientation to the orientation with the maximum misorientation around 30°. Recrystallization kinetics and maps were constructed based on the Johnson–Mehl– Avrami–Kolmogorov (JMAK) equation to derive parameters sensitive to the microstructure. The activation energies for recrystallization of 30%, 50% and 70% cold-rolling reductions were determined to be 240, 249 and 180 kJ/mol, respectively.

Friction stir modification of GTA 7075-T6 Al alloy weld joints: EBSD study and microstructural evolutions

As known, mechanical properties of gas tungsten arc welded 7075 Al alloys are not desirable and some techniques should be utilized in order to refine the microstructure and hence to improve the mechanical properties of weld joints. In this research work, the microstructure of gas tungsten arc welded 7075 Al alloy was modified by friction stir processing. Evaluation of the tensile strength of the welded joints showed that the tensile strength of the welded joint (228MPa) increases up to 320MPa after friction stir processing. In addition, electron backscattered diffractometry (EBSD) was used in order to study the microstructure and grain boundary character evolutions during arc welding and friction stir processing. It was revealed that as-cast dendritic microstructure of gas tungsten arc welded joint completely disappears during friction stir processing and very fine equiaxed grains are formed in welded joints. Analysis of EBSD data showed that friction stir processing of gas tungsten arc welded joints leads to increase of specific boundaries from 0.7% up to 7.8%. In addition, fraction of high angle boundaries increases after friction stir processing which is resulted from dynamic recrystallization occurring during friction stir processing.

Morphological Characteristics of Retained Austenite in 0.362C–1.38Si–1.24Mn Steel Processed by One-Step Quenching and Partitioning

The microstructure and morphology of retained austenite are effective parameters in the mechanism of plasticity enhancement in quenching and partitioning steels. This study focused on the identification of morphological features of retained austenite through scanning electron microscopy, field emission-scanning electron microscopy, electron backscatter diffractometry, and transmission electron microscopy in a onestep quenched and partitioned C–Mn–Si steel. Retained austenite of different sizes and shapes (island-like and film-like) and martensite with lath-type morphology were observed at all partitioning times. Cementitecarbide (Fe3C) precipitates with a dominant spherical shape and average submicron size were also characterized in samples that had been partitioned for longer times.

Challenges and strategies of surface modification of electrogalvanized coatings for electron microscopy analysis

Despite wide usage of electrogalvanized coatings in various applications, characterization studies on their micro/crystal structure, and the understanding of how they correspondingly affect the properties, such as corrosion, are rather limited. This is mainly attributed to some difficulties in preparing and examining the zinc coating layers, owing to their intrinsically low corrosion resistance and refined nano-scaled crystallite size. This study aims to examine such challenges systematically and propose some mitigation strategies. Particularly, sample preparation processes, including surface finishing for metallography and sample thinning processes are explored. Furthermore, a range of electron microscopy techniques, including scanning electron microscopy (SEM), electron back scattered diffractometry (EBSD), and transmission electron microscopy (TEM) are investigated in relation to the achievable clarity of microstructural details of electrogalvanized coatings.

The strain accommodation in Ti–28Nb–12Ta–5Zr alloy during warm deformation

The warm deformation behavior of a β-type Ti alloys, composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt, (so called TNTZ alloy), has been investigated in the present work in a warm deformation temperature. A variety of deformation features are characterized in the material microstructure after applied warm deformation scheme. The XRD analysis confirms an enhancement in martensite volume fraction. The electron back scatter diffractometry (EBSD) elucidates that the martensite has been mainly formed by laterally at the vicinity of different types of deformation bands. Both the well-known twining systems in TNTZ series have been occurred during deformation. The micro-shear bands, which are defined as highly concentrated plastic strain regions, are characterized in the deformed microstructure. The micro-shear bands are severely formed in the regions, which accommodate the most amount of applied strain.

Statistical Analysis on Static Recrystallization Texture Evolution in Cold-Rolled AZ31 Magnesium Alloy Sheet

Cast AZ31B-H24 magnesium alloy, comprising Mg with 3.27 wt% Al and 0.96 wt% Zn, was cold rolled and subsequently annealed. Global texture evolutions in the specimens were observed by X-ray diffractometry after the thermomechanical processing. Image-based microstructure and texture for the deformed, recrystallized, and grown grains were observed by electron backscattered diffractometry. Recrystallized grains could be distinguished from deformed ones by analyzing grain orientation spread. Split basal texture of ca. ±10-15° in the rolling direction was observed in the cold-rolled sample. Recrystallized grains had widely spread basal poles at nucleation stage; strong {0001} basal texture developed with grain growth during annealing.

The effects of Si on the mechanical twinning and strain hardening of Fe–18Mn–0.6C twinning-induced plasticity steel

The stacking-fault energy (SFE), dislocation slip, mechanical twinning, strain hardening, and yield and tensile strengths were systemically investigated in Fe–18Mn–0.6C–1.5Si twinning-induced plasticity (TWIP) steel. The results were also compared with those for Fe–18Mn–0.6C and Fe–18Mn–0.6C–1.5Al TWIP steels. The SFE decreased by 4mJm−2 per 1wt.% Si. The addition of Si increased both the yield strength, due mainly to solid solution hardening, and the tensile strength, owing to the high strain hardening that occurred while maintaining a large elongation of over 60%. To examine this high strain hardening, especially at low strains, the volume fractions of the primary and secondary mechanical twins were quantitatively evaluated by combining the merits of electron backscattered diffractometry and transmission electron microscopy. The volume fractions of both the primary and secondary twins were the highest in the Fe–18Mn–0.6C–1.5Si TWIP steel, which had the lowest SFE of the three TWIP steels. In particular, the volume fraction of the secondary mechanical twins increased rapidly with the addition of Si. The contributions of dislocation storage, mechanical twinning and dynamic strain aging (DSA) to the strain hardening were also quantitatively evaluated in the three TWIP steels. The Si-added TWIP steel had the highest strain hardening, due mainly to the active primary and secondary twinning, and experienced negligible DSA. In contrast, the Al-added TWIP steel exhibited the lowest strain hardening due to the reductions in both the mechanical twinning and DSA.

Texture evolution and its simulation of cold drawing copper wires produced by continuous casting

The texture evolution of cold drawing copper wires produced by continuous casting was measured by X-ray diffractometry and electron back-scatter diffractometry, and was simulated using Taylor model. The results show that in the drawn poly-crystal copper wires produced by traditional continuous casting, 〈111〉 and 〈100〉 duplex fiber texture forms, and with increasing strain, the intensities of 〈111〉 and 〈100〉 increase. In the drawn single-crystal copper wires produced by Ohno continuous casting, 〈100〉 rotates to 〈111〉, and there is inhomogeneous distribution of fiber texture along radial direction of the wires, which is caused by the distribution of shear deformation. Compared with 〈100〉, 〈111〉 fiber texture is more stable in the drawn copper wires. Comparison of the experimental results with the simulated results shows that the simulation by Taylor model can analyze the texture evolution of drawn copper wires.