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 Acta Metallurgica Sinica (English Letters)Journal Prestige (SJR): 0.576 Citation Impact (citeScore): 2Number of Followers: 10      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1006-7191 - ISSN (Online) 2194-1289 Published by Springer-Verlag  [2658 journals]
• Nature of CoCrFeMnNi/Fe and CoCrFeMnNi/Al Solid/Solid Interface

Abstract: To shed light into the application potential of high-entropy alloys as “interlayer” materials for Al-steel solid-state joining, we investigated the nature of the CoCrFeMnNi/Fe and CoCrFeMnNi/Al solid/solid interfaces, focusing on the bonding behavior and phase components. Good metallurgical bonding without the formation of hard and brittle IMC can be achieved for CoCrFeMnNi/Fe solid/solid interface. In contrast to the formation of Al5Fe2 phase at the Fe/Al interface, Al13Fe4-type IMC, in which the Fe site is co-occupied equally by Co, Cr, Fe, Mn and Ni, dominates the CoCrFeMnNi/Al interface. Although the formation of IMC at the CoCrFeMnNi/Al interface is not avoidable, the thickness and hardness of the Al13(CoCrFeMnNi)4 phase formed at the CoCrFeMnNi/Al interface are significantly lower than the Al5Fe2 phase formed at the Fe/Al interface. The activation energies for the interdiffusion of Fe/Al and CoCrFeMnNi/Al static diffusion couple are 341.6 kJ/mol and 329.5 kJ/mol, respectively. Despite this similarity, under identical static annealing condition, the interdiffusion coefficient of the CoCrFeMnNi/Al diffusion couple is significantly lower than that of the Fe/Al diffusion couple. This is thus mainly a result of the reduced atomic mobility/diffusivity caused by the compositional complexity in CoCrFeMnNi high-entropy alloy.
PubDate: 2021-10-10

• Application of Synchrotron X-Ray Imaging and Diffraction in Additive
Manufacturing: A Review

Abstract: Additive manufacturing (AM) is a rapid prototyping technology based on the idea of discrete accumulation which offers an advantage of economically fabricating a component with complex geometries in a rapid design-to-manufacture cycle. However, various internal defects, such as balling, cracks, residual stress and porosity, are inevitably occurred during AM due to the complexity of laser/electron beam-powder interaction, rapid melting and solidification process, and microstructure evolution. The existence of porosity defects can potentially deteriorate the mechanical properties of selective laser melting (SLM) components, such as material stiffness, hardness, tensile strength, and fatigue resistance performance. Synchrotron X-ray imaging and diffraction are important non-destructive means to elaborately characterize the internal defect characteristics and mechanical properties of AM parts. This paper presents a review on the application of synchrotron X-ray in identifying and verifying the quality and requirement of AM parts. Defects, microstructures and mechanical properties of printed components characterized by synchrotron X-ray imaging and diffraction are summarized in this review. Subsequently, this paper also elaborates on the online characterization of the evolution of the microstructure during AM using synchrotron X-ray imaging, and introduces the method for measuring AM stress by X-ray diffraction (XRD). Finally, the future application of synchrotron X-ray characterization in the AM is prospected.
PubDate: 2021-10-09

• Unveiling the Growth Mechanism of Faceted Primary Al2Cu with Complex
Morphologies During Solidification

Abstract: The growth characteristic of primary faceted Al2Cu intermetallic compounds (IMCs) during solidification was observed directly by synchrotron radiography. The formation and transition mechanisms of Al2Cu IMCs with diverse morphologies were elucidated by first-principle calculations combined with electron backscatter diffraction analysis. The Al2Cu crystals preferred to grow along the [001] direction and were bounded by {110} planes with the lowest surface energy. The faceted Al2Cu rod-like clusters consisted of multiple crystals with complete rod, hollowness and partial sides, which was attributed to the increase in strain energy and solute redistribution during solidification. The faceted Al2Cu with branches was characteristic with the perpendicular relationship between the main branches and side steps and partial coalescence at the junction, which was ascribed to the continuous propagation and growth of newly formed crystals along the diagonal direction.
PubDate: 2021-10-08

• Correction to: Effects of Homogenization Treatment on the Microsegregation
of a Ni–Co Based Superalloy Produced by Directional Solidification

Abstract: In the original publication of the article, the Chinese title and author names appeared inadvertently in the Ref. [24].
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01271-9

Dimension Tolerance of AZ31 Magnesium Alloy Assisted by Stationary
Shoulder: Process and Mechanical Properties

Abstract: Radial additive friction stir repairing (R-AFSR) assisted by stationary shoulder was put forward in the present study, which can be employed to repair the mechanical hole out of dimension tolerance of AZ31 magnesium alloy sheet. The results show that the stationary shoulder has sealed-barrier, heat-sink and extra-forging effects. The heat-sink effect improves the microstructure uniformity along the stir zone (SZ) thickness and the surface appearance of repaired hole, and the sealed-barrier and extra-forging effects eliminate the super-fine grain band in the SZ. Therefore, these three effects improve the formation quality of repaired region, thereby enhancing the mechanical properties of repaired mechanical hole compared with conventional R-AFSR. The tensile and compressive shear strengths of the repaired hole by stationary shoulder R-AFSR both increase first and then decrease when the rotating speed changes from 1200 to 1800 rpm, and these maximum values, respectively, reach 190 ± 3 MPa and 64.5 ± 2 MPa at 1400 rpm. The addition of stationary shoulder during R-AFSR can obtain a higher-quality repaired hole and broaden the repairing process window.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01223-3

• Effect of Particle Size on Mechanical Properties and Fracture Behaviors of
Age-Hardening SiC/Al–Zn–Mg–Cu Composites

Abstract: 15 vol.% SiC/Al-6.5Zn-2.8 Mg-1.7Cu (wt%) composites with varying particle sizes (3.5, 7.0, 14 and 20 μm), i.e., C-3.5, C-7.0, C-14, and C-20, respectively, were fabricated by powder metallurgy (PM) method and subjected to microstructural examination. The effect of particle size on mechanical properties and fracture behaviors of the T6-treated composites was revealed and analyzed in detail. Element distribution and precipitates variations in the composites with varying particle sizes were emphatically considered. Results indicated that both tensile strength and plasticity of the T6-treated composites increased first and then decreased with particle size decreasing. The C-7.0 composite simultaneously exhibited the highest ultimate tensile strength (UTS) of 686 MPa and best elongation (El.) of 3.1%. The smaller-sized SiC particle would introduce more oxide impurities, which would react with the alloying element in the matrix to cause Mg segregation and depletion. According to strengthening mechanism analysis, the weakening of precipitation strengthening in the T6-treated C-3.5 composite was the main cause of the lower tensile strength. Additionally, the larger SiC particle, the more likely to fracture, especially in the composites with high yield strength. For the T6-treated C-20 composites, more than 75% SiC particles were broken up, resulting in the lowest plasticity. As decreasing particle size, the fracture behaviors of the T6-treated composites would change from particle fracture to matrix alloy fracture gradually.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01254-w

• Numerical Prediction of Intermetallic Compounds Thickness in Friction Stir
Welding of Dissimilar Aluminum/Magnesium Alloys

Abstract: An atomic diffusion model is developed to predict the thickness of intermetallic compounds (IMCs) at the interface of aluminum/magnesium alloys in dissimilar friction stir welding. Both the temperature and the strain rate associated with dislocation density at the checking point are used to determine the diffusion coefficients. The variations of the diffusion coefficients and the thickness of IMCs are quantitatively analyzed at selected characteristic time instants during welding process. It is found that the dislocation density can increase the diffusion coefficient and plays a dominant role in the IMCs formation during the plastic deformation stage. Especially in magnesium alloy and Al12Mg17, the diffusion coefficient is increased by two orders of magnitude or even nearly three orders of magnitude by considering the dislocation density. The temperature is the main influencing factor after the end of plastic deformation. The model is validated by comparing the predicted thickness of IMCs with the experimentally measured results.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01238-w

• Effect of Rotation Rate on Microstructure and Mechanical Properties of
Friction Stir Processed Ni–Fe-Based Superalloy

Abstract: In this work, friction stir processing (FSP) was applied to the high-strength and high-melting-point Ni–Fe-based superalloy (HT700) for the first time with negligible wear of the stir tool. Different rotation rates were chosen to investigate the effect of heat input on microstructure and tensile properties at different temperatures of friction stir processed Ni–Fe-based superalloy. The results showed that with increasing rotation rate, the percentage of high-angle grain boundaries and twin boundaries gradually decreased whereas the grain size initially increased and then remained almost constant; the difference in tensile properties of FSP samples with rotation rates of 500–700 rpm was small attributing to their similar grain size, but the maximum strength was achieved in the FSP sample with a rotation rate of 400 rpm and traverse speed of 50 mm/min due to its finest grain size. More importantly, we found that the yield strength of all FSP samples tensioned at 700 °C was enhanced clearly resulting from the reprecipitation of γ′ phase. In addition, the grain refinement mechanism of HT700 alloy during FSP was proved to be continuous dynamic recrystallization and the specific refinement process was given.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01240-2

• Heterogeneous Microstructure-Induced Mechanical Responses in Various
Sub-Zones of EH420 Shipbuilding Steel Welded Joint Under High Heat Input
Electro-Gas Welding

Abstract: Heterogeneous microstructure-induced mechanical responses in EH420 shipbuilding steel welded joint by electro-gas welding processed have been systematically studied by scanning electron microscopy, electron backscatter diffraction and mechanical testing. Comparing with the coarse-grained heat-affected zone (CGHAZ), the weld metal presents higher toughness (129.3 J vs. 37.3 J) as it contains a large number of acicular ferrites with high-angle grain boundaries (frequency 79.2%) and special grain boundary ∑3 (frequency 55.3%). Moreover, coarse austenite grains in CGHAZ and slender martensite–austenite constituents between bainite laths may likely facilitate crack propagation. Polygonal ferrites and tempered pearlites formed at the junction of the fine-grained heat-affected zone and the intercritical heat-affected zone induced a softened zone with an average hardness of 185 HV0.5, which is the main reason for the occurrence of tensile fracture.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01245-x

• Effects of Gd Addition on the Microstructure and Tensile Properties of
Mg–4Al–5RE Alloy Produced by Three Different Casting Methods

Abstract: This work deals with the effect of 0.67 wt% Gd addition on the microstructure and tensile properties of Mg–4Al–5RE (where RE represents La–Ce mischmetal) alloy produced by sand casting (SC), permanent mold casting (PMC), and high-pressure die casting (HPDC). The results show that Gd addition could refine the grains, but its efficiency decreases by increasing the cooling rate due to the shifting from SC to PMC and finally to the HPDC method. Meanwhile, the acicular Al11RE3 phase is modified into the short-rod or granular-like shape under the three casting conditions. Such refined and modified microstructures are due to the Al2(Gd, RE) phases, which act as the nucleation sites in both the α-Mg matrix and Al11RE3 phase. Also, the weakening grain refinement effect in the increased cooling rates can be attributed to the narrow constitutional undercooling zone. After Gd addition, the 0.2% proof strength of the SC and PMC alloys increases by about 16.9% and 12.7%, respectively, while in the HPDC alloy, it decreases by about 5.9%. The main factor in the strength increment of the SC and PMC alloys is the grain boundary strengthening due to grain refinement which is proved by modeling the related mechanisms, whereas weak secondary phases and grain boundary strengthening mechanisms in the HPDC alloy lead to strength reduction. After Gd addition, the elongation to failure of the SC, PMC, and HPDC alloys is significantly enhanced by about 34.8%, 20.2%, and 12.3%, respectively, due to the crack resistance nature of the modified short-rod/granular Al11(RE, Gd)3 phase compared to the acicular one.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01276-4

• Synchronously Improving the Thermal Conductivity and Mechanical Properties
of Al–Si–Fe–Mg–Cu–Zn Alloy Die Castings Through
Ultrasonic-Assisted Rheoforming

Abstract: An ultrasonic vibration-assisted air-cooled stirring rod process (ACSR + UV) was used to efficiently prepare a large-volume semisolid slurry with a mass of more than 40 kg. A low-cost Al–Si–Fe–Mg–Cu–Zn die-casted alloy with high thermal conductivity, high plasticity and medium strength was developed. The alloy was used to manufacture large, thin-walled parts for 5G base stations by using the ACSR + UV rheological die-casting (ACSR + UV R-DC) process. Investigations were performed on the microstructure, porosity, mechanical properties, fracture behaviour and thermal conductivity of the ACSR + UV R-DC alloy, which was then compared to traditionally die-casted (T-DC) and ACSR R-DC alloys. The mechanisms for the microstructural refinement and enhancement of the mechanical and thermal conductivity performances of the ACSR + UV R-DC alloy were also analysed. The results showed that the ACSR + UV process increased the nucleation rate of the melt due to the increase in the nucleation area and the generation of cavitation bubbles. A radial- and an axial-forced convection was also generated inside the melt under the combined effects of acoustic flow and mechanical stirring, thereby homogenising the melt composition field and the temperature field. Therefore, the ACSR + UV R-DC process not only refined the primary α-Al (α1-Al), the eutectic silicon and the secondary α-Al (α2-Al), but also greatly improved the morphology and the distribution of the β-Al5FeSi phase. The mechanical properties of the ACSR + UV R-DC alloy were higher than those of the T-DC and the ACSR R-DC alloys. Compared to the T-DC alloy, the ultimate tensile strength, elongation and yield strength of the ACSR + UV R-DC alloy were increased by 34%, 122% and 19%, respectively. This was because the ACSR + UV R-DC technique gave the alloy the characteristics of high density, fine spherical α1-Al grain and a fine and uniform β-phase, which improved the fracture behaviour of the alloy. The thermal conductivity of the ACSR + UV R-DC alloy was 184 W/(m K), which was 10.2% and 3.4% higher than that of T-DC and ACSR R-DC alloys, respectively. This was because the refined eutectic silicon and β phases in the ACSR + UV R-DC alloy facilitated an easier electron flow through the eutectic region, and the decrease in porosity increased the effective area of heat conduction.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01231-3

• Corrosion Behaviors of Nitride Coatings on Titanium Alloy in NaCl-Induced
Hot Corrosion

Abstract: TiN and TiAlN coatings were deposited by arc ion plating on titanium alloys to study their hot corrosion resistance when they were exposed to NaCl at 600 °C. The microstructure and corrosion behaviors of nitride coatings were studied using scanning electron microscope, X-ray diffraction, electro-probe microanalyzer and X-ray photoelectron spectroscopy. The results showed that nitride coatings with the different compositions and the ones with the same composition but different thicknesses presented different hot corrosion resistance. TiN and thin TiAlN coatings showed poor corrosion resistance. Serious internal oxidation attacked the alloy substrate. Their corrosion products were mainly consisted of non-protective TiO2 and sodium salt. By contrast, the thick TiAlN coating presented outstanding corrosion resistance. Besides sodium salt, the corrosion products were composed of protective Al2O3. The increasing thickness of TiAlN significantly enhanced the hot corrosion resistance. The corrosion mechanisms of alloy, TiN and TiAlN coatings were discussed in detail.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01264-8

• Influence of Filler on the Microstructure, Mechanical Properties and
Residual Stresses in TIG Weldments of Dissimilar Titanium Alloys

Abstract: The influence of titanium alloy (Ti–5Al–2.5Sn) and commercially pure titanium (cpTi) as fillers on dissimilar pulsed tungsten inert gas weldments of Ti–5Al–2.5Sn/cpTi was investigated in terms of microstructure, mechanical/nano-mechanical properties, and residual stresses. A partial martensitic transformation was observed in the weldments for all the welding conditions due to high heat input. The microstructure evolved in the FZ/cpTi interfacial region was observed to be the most sensitive to the proportion of α stabilizer in the filler alloy. Furthermore, the addition of filler alloy improved the tensile properties and nano-mechanical response of the weld joint owing to the increased volume of metal in the weld joint. As compared to the Ti–5Al–2.5Sn wire, the use of cpTi filler wire proved to be better in terms of energy absorbed during tensile and impact tests, tensile strength and ductility of the dissimilar welds. An asymmetrical residual stresses profile was observed close to the weld centerline, with high compressive stresses on the Ti–5Al–2.5Sn side for both the weldments obtained with and without filler wires. This was attributed to mainly the low thermal conductivity of Ti–5Al–2.5Sn. The presence of residual stresses also influenced the nano-hardness profile across the weldments.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01236-y

• Tribological Behavior of In Situ TiC/Graphene/Graphite/Ti6Al4V Matrix

Abstract: The TiC/graphene/graphite/Ti6Al4V composite coating was prepared by laser cladding. The microstructure and tribological behavior of the coating were studied. The in situ reaction between graphene and Ti occurred, and feathery TiC was formed. The feathery TiC was homogeneously distributed between α' acicular martensites which was refined with the addition of graphene. Some graphene was transformed into allotrope graphite under the laser irradiation. The TiC hard particles and the self-lubrication of graphene/graphite improved the wear resistance of composite coating. The wear rate and friction coefficient of TiC/graphene/graphite/Ti6Al4V composite coating decreased with the increase in sliding speed, a mechanical mixing layer (MML) was formed on the wear surface of the composite coating under the frictional heat, which protected the substrate and reduced the contact. Because of the self-lubricating properties of graphene/graphite, interlayer sliding occurred easily, which also effectively reduced friction. The wear rate of TiC/graphene/graphite/Ti6Al4V composite coating increased with the increase in load, but the friction coefficient decreased. The plastic deformation of subsurface layer was more serious under high load, and a stable self-lubricating MML with a protective effect was formed between the wear interfaces, which reduced the friction coefficient. With the increase in load, the wear mechanism changed from abrasive and oxidation wear to delamination, fatigue and oxidation wear.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01215-3

• Effect of Argon-Induced Porosity on Mechanical Properties of Powder
Metallurgy Titanium Alloy Components using Hot Isostatic Pressing

Abstract: This work reported the Ar-induced porosity in powder metallurgy Ti-5Al-2.5Sn alloy prepared by hot isostatic pressing (HIPing). The obtained microstructures of powder compacts were studied through optical and scanning electron microscopes, X-ray tomography, and the mechanical properties evaluated through tensile and impact tests. The results showed that the Ar-induced porosity is related to the hollow powder with gas bubble and the Ar leakage of sealed container during the powder densification. The hollow powder with gas bubble shows no obvious effects on mechanical properties of as-HIPed powder compacts. The Ar content decreases with the increasing shrinkage of encapsulated powder. 0.7% Ar-induced porosity degrades the impact toughness, but no reductions of tensile properties were obtained. Ar content test is an effective method to detect the powder compacts with Ar concentration.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01243-z

• Phase-Field Modeling of Hydrogen Diffusion and Trapping in Steels

Abstract: Hydrogen embrittlement of steels is directly linked to hydrogen diffusion and trapping in the microstructure, which can hardly be precisely measured by modern experimental techniques. A phase-field model, in which a chemical potential well of hydrogen in the grain boundaries is introduced, is proposed to simulate hydrogen diffusion and trapping in the polycrystalline iron. It was interestingly found that grain boundaries, as connected trap sites, have a complex influence on the effective diffusivity of hydrogen, which are strongly linked to grain boundary diffusivity and binding energy.
PubDate: 2021-10-01
DOI: 10.1007/s40195-021-01241-1

• Effect of Carbon Migration on Interface Fatigue Crack Growth Behavior in
9Cr/CrMoV Dissimilar Welded Joint

Abstract: Fatigue crack growth (FCG) behavior of 9Cr/CrMoV dissimilar welded joint at elevated temperature and different stress ratios was investigated. Attention was paid to the region near the fusion line of 9Cr where carbon-enriched zone (CEZ) and carbon-depleted zone (CDZ) formed due to carbon migration during the welding process. Hard and brittle tempered martensite dominated the stress ratio-insensitive FCG behavior in the coarse grain zone (CGZ) of 9Cr-HAZ. For crack near the CGZ–CEZ interface, crack deflection through the CEZ and into the CDZ was observed, accompanied by an accelerating FCG rate. Compared with the severe plastic deformation near the secondary crack in 9Cr-CGZ, the electron back-scattered diffraction analysis showed less deformation and lower resistance in the direction toward the brittle CEZ, which resulted in the transverse deflection. In spite of the plastic feature in CDZ revealed by fracture morphology, the less carbides due to carbon migration led to lower strength and weaker FCG resistance property in this region. In conclusion, the plasticity deterioration in CEZ and strength loss in CDZ accounted for the FCG path deflection and FCG rate acceleration, respectively, which aggravated the worst FCG resistance property of 9Cr-HAZ in the dissimilar welded joint.
PubDate: 2021-09-29

• Synchrotron Characterisation of Ultra-Fine Grain TiB2/Al-Cu Composite
Fabricated by Laser Powder Bed Fusion

Abstract: Isotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.
PubDate: 2021-09-29

• Revealing the Diversity of Dendritic Morphology Evolution During
Solidification of Magnesium Alloys using Synchrotron X-ray Imaging: A
Review

Abstract: In this paper, the diversity of complicated dendrite microstructure and its evolution behavior during solidification in different magnesium alloys under various processing conditions were illustrated using synchrotron X-ray imaging technique. A variety of dendritic morphologies and branching structures were revealed, i.e., sixfold plate-like symmetric structure in Mg–Al-based structure, 12-branch structure in Mg–Zn-based alloys and 18-branch structure in Mg–Sn- and Mg–Ca-based alloys as well as seaweed like hyper-branched structure in Mg-38wt%Zn alloy. In addition, a dendrite morphology and orientation transition with increasing addition of Zn content were also observed in Mg–Zn alloy, with dendrite growth pattern transform from anisotropy (low Zn addition) with sixfold symmetric snow-flake structure to relative isotropy (intermediate Zn addition) where seaweed morphology presented and then back to anisotropy (high Zn addition) when only 12 branches with preferred < 11 $$\overline{2}$$ 1 > orientations were observed. The phase-field model representing the typical dendritic morphologies and branching structures under various conditions was also depicted and discussed. Further, the two-dimensional (2D) real-time dendrite growth dynamics in different Mg-based alloys captured using synchrotron X-ray radiography for unveiling the originate of the α-Mg dendrite was reviewed. Following this, the four-dimensional (3D + time) synchrotron X-ray tomographic in situ observation of dendritic morphology evolution indicating the formation mechanism of the diverse dendritic morphology during Mg–Sn- and Mg–Zn-based alloys was also summarized. Finally, the future study on exploring the complicated dendritic morphologies and their origination during solidification of Mg-based alloys is prospected.
PubDate: 2021-09-28

• Additive Manufacturing of Nickel-Based Superalloy Single Crystals with
IN-738 Alloy

Abstract: The production of non-weldable nickel-based superalloys, especially single-crystal superalloys, is important for additive manufacturing. Single-crystal specimens of non-weldable nickel-based superalloys were produced by electron beam selective melting using an IN-738 alloy. In this study, single-crystal nickel-based superalloy specimens of different sizes were prepared by a multiple preheating process and tight control of the melting parameters without the need for a grain selector or single-crystal seed for the first time. Electron backscattered diffraction measurements were performed to confirm the presence of a single crystal. The transition boundaries between the polycrystalline and single-crystal regions at the edges and bottom of the samples were characterized to analyze the formation of single crystals.
PubDate: 2021-09-27

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