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High entropy alloys (HEAs) are being attracted recently by several researchers, scientists, and academicians to achieve extraordinary and outstanding properties that cannot be obtained from conventional alloys. HEAs are multicomponent alloys in which a minimum of five metallic elements are mixed in an equal molar or non-equal molar ratio. The rapid...
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... atomization is the one technique in which the molten metallic materials are directly converted into solid powder particles by gas or liquid stream. Figure 4 shows the schematic of the powder atomization process. Atomization device is usually consisting of two-stage: the first one is the furnace chamber in which the metallic powders called the charge are melt in a vacuum atmosphere to the required temperature, then the second one is the molten melt liquid drain through a nozzle which is located at the bottom of the tundish into atomizing chamber. ...
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... one is the molten melt liquid drain through a nozzle which is located at the bottom of the tundish into atomizing chamber. As the molten melt continuously flows inside the tundish by gravity, the atomizing nozzle has disintegrated the liquid stream of melt into tiny droplets by high-pressure gas or water jet; which then solidified immediately (Fig. 4) led to form sold powder particles. The metal powders particle size is affected by the coolant distance, coolant pressure, coolant velocity, coolant mass flow rate, liquid stream velocity, and liquid mass flow rate, angle of impingement, superheat, metal surface tension and metal meting range [32]. Table 1 shows the range of those ...
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... procedure steps when compared to the conventional sintering techniques. Further, a homogeneous bulk single SS alloy can be retained after processing with improved microstructural features and mechanical properties. The principle idea of SPS is that the pressure ram which is work as electrode attached to direct current (DC) source as shown in Fig. 14. The DC is infiltrated (750-1500 A) through the powders by the graphite punch simultaneously the powder particles are being compressed (25-150 MPa). Using SPS, very high dense products with nanostructures and limited grain growth can be achieved based on desired sintering parameters. Eißmann et al. [56] have consolidated CoCrFeMnNi HEA ...
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... Fu et al. [52] investigated non-equiatomic FCC Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEAs processed by PM route (MA and SPS) and casting route. The results explained that around 1.8 GPa YS and 4.6 GPa VHS were obtained in HEA via PM route which was 835% high in YS and 252% more in hardness when compared to cast one. These improved results were due to Fig. 14 Schematic of the working principle of spark plasma sintering (SPS) process Fig. 15 a SEM image of spark plasma sintered CoCrFeMnNi HEA; b corresponding XRD patterns for as-milled powder and after SPS [56] grain boundary strengthening and dislocation strengthening mechanisms (see ...
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... and then the HEA was processed through the DS process. Here, first, the HEA was melted, hold it for 60 min inside an 8 mm diameter with a length of 150 mm Al 2 O 3 ceramic tube, and then the velocity of melt was varied into Ga-In-Sn coolant. After solidification in a single direction, the HEA produced a stable and homogeneous columnar grain (Fig. 24). The obtained results explained that the UTS started to increases with the function of downward velocity whereas the columnar grain size started to decreases. The fabricated CoCrFeNi HEA with 50 μm/s sample produced UTS of 0.6 GPa which was 1.39 times more compared to the same HEA processed with a velocity of 5 μm/s ...
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... parameters of each element. The presence of high configurational entropy decreases the amount of free energy in HEAs according to Gibbs free energy equation (see "Appendix of ESM") due to which stabilized solid solutions phase can be obtained even at high temperatures. Among the discussed manufacturing methods, gas atomized HEAs powders ( Fig. 4) followed additive manufacturing technology (Fig. 32), MA powders ( Fig. 7 followed SPS (Fig. 14), vacuum induction melting (Fig. 22), directional solidification (Fig. 23), magnetron sputtering (Fig. 28), and laser deposition ( Fig. 29) techniques can produce single phase-stable HEAs by which extensive mechanical properties could be ...
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... decreases the amount of free energy in HEAs according to Gibbs free energy equation (see "Appendix of ESM") due to which stabilized solid solutions phase can be obtained even at high temperatures. Among the discussed manufacturing methods, gas atomized HEAs powders ( Fig. 4) followed additive manufacturing technology (Fig. 32), MA powders ( Fig. 7 followed SPS (Fig. 14), vacuum induction melting (Fig. 22), directional solidification (Fig. 23), magnetron sputtering (Fig. 28), and laser deposition ( Fig. 29) techniques can produce single phase-stable HEAs by which extensive mechanical properties could be obtained. This meant, the formation of second phase particles/precipitates, and or IMCs can almost ...
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... considerably. For instance, AlCoCrFeNi HEA in as-cast and heat-treated behavior is illustrated that an improvement in ductility with plastic strains as the aged temperature increases [93]. Rao et al. [94] investigated the aging behavior of Fe 0.4 Cr 0.4 NiMnCu HEA which was aged at two different temperatures (900 °C and 1000 °C for 24 h (Fig. 34). From Fig. 34a, b, it was ensured a homogenized FCC phase and a small amount of dendrite phase in the form of needle-like shapes after aging. The HEA aged at 900 °C was exhibited interdendritic phase whereas HEA aged at 1000 °C was exhibited uniform dispersion of needle-like phase which corresponds to the BCC phase. The XRD pattern of ...
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... et al. [94] investigated the aging behavior of Fe 0.4 Cr 0.4 NiMnCu HEA which was aged at two different temperatures (900 °C and 1000 °C for 24 h (Fig. 34). From Fig. 34a, b, it was ensured a homogenized FCC phase and a small amount of dendrite phase in the form of needle-like shapes after aging. The HEA aged at 900 °C was exhibited interdendritic phase whereas HEA aged at 1000 °C was exhibited uniform dispersion of needle-like phase which corresponds to the BCC phase. ...
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... h (Fig. 34). From Fig. 34a, b, it was ensured a homogenized FCC phase and a small amount of dendrite phase in the form of needle-like shapes after aging. The HEA aged at 900 °C was exhibited interdendritic phase whereas HEA aged at 1000 °C was exhibited uniform dispersion of needle-like phase which corresponds to the BCC phase. The XRD pattern of Fig. 34c for HEA aged at 1000 °C was clearly shown the formation of the BCC phase which was conformed as per Fig. 34b. The true stress-true strain curves of as-cast and homogenized Fe 0.4 Cr 0.4 NiMnCu HEA is also shown in Fig. 34d. The result was explained that homogenized HEA exhibited more strength when compared to as-cast one. However, a ...
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... the form of needle-like shapes after aging. The HEA aged at 900 °C was exhibited interdendritic phase whereas HEA aged at 1000 °C was exhibited uniform dispersion of needle-like phase which corresponds to the BCC phase. The XRD pattern of Fig. 34c for HEA aged at 1000 °C was clearly shown the formation of the BCC phase which was conformed as per Fig. 34b. The true stress-true strain curves of as-cast and homogenized Fe 0.4 Cr 0.4 NiMnCu HEA is also shown in Fig. 34d. The result was explained that homogenized HEA exhibited more strength when compared to as-cast one. However, a homogenized HEA sample produces decreased ductility due to dendrite BCC phase precipitates. Therefore, it is ...
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... aged at 1000 °C was exhibited uniform dispersion of needle-like phase which corresponds to the BCC phase. The XRD pattern of Fig. 34c for HEA aged at 1000 °C was clearly shown the formation of the BCC phase which was conformed as per Fig. 34b. The true stress-true strain curves of as-cast and homogenized Fe 0.4 Cr 0.4 NiMnCu HEA is also shown in Fig. 34d. The result was explained that homogenized HEA exhibited more strength when compared to as-cast one. However, a homogenized HEA sample produces decreased ductility due to dendrite BCC phase precipitates. Therefore, it is clear that the properties of HEAs are highly influenced by the phase formation, various processing methods, and ...
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... 0.141 to 5.8 GPa was achieved in CoCrFeNiTa 0.4 HEA [102]. Further, some studies have investigated the corrosion behavior of HEAs [70,71,93,103]. It was also observed from Table 3 that the tensile strength and hardness were decreased slightly as the temperature started to increase in all the HEAs. The mechanical behavior of some HEAs is shown Fig. 34. The variation of the atomic fraction of some element(s) in HEAs influences much on mechanical behavior. For instance, The UTS of CoCrFeNiTa 0.4 HEA exhibited more value compared to CoCrFeNiTa 0.75 HEA [102] likewise, Al 0.3 CoCrFeNiMn 0.3 has UST of 371MPA more than Al 0.3 CoCrFeNiMn 0.1 which has exhibited UST of 336 MPa [99]. The ...
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... For instance, the compressive strain of around 27% was obtained in TiNbMoTaW REHEA whereas TiVNbTaMoW HEA produced the compressive strain of only 4% [106]. Some other research articles demonstrate the mechanical properties change by varying any one element in HEA. Incorporation of Ti x in Ti x NbMoTaW HEA increases the UTS with an increment Fig. 34 a and b Backscattered electron SEM images of homogenized Fe 0.4 Cr 0.4 NiMnCu HEA at two different temperatures after 24 h, c corresponding XRD pattern of 1000 °C homogenized sample, and d true stress-true strain curves of as-cast and homogenized at 1000 °C ...
Citations
... Induction melting, additive manufacturing, powder metallurgy, additive manufacturing, vacuum arc melting, plasma sintering of powders, and other metallurgical methods can be used to create HEAs [4,9,10]. Due to the high level of protection of the melts, the production process in the vacuum arc melting plant provides outstanding uniformity characteristics for metal matrices while also providing enhanced purity [5,11]. Varalakshmi et al. [12] discovered that mechanical alloyed HEAs shows high compositional homogeneity. ...
The AlCrFeCuNi-(Vx) High Entropy Alloy (HEA) was created via arc-melting and casting processes. The influence of vanadium (V) on the Nano mechanical behaviour, microstructural development, as well as the wear performance of the produced HEAs was examined. Notable improvements to the Nano hardness of the HEAs were evident with an increase in V content from 1at% to 5at%. The addition of V altered the frictional behaviour of the HEA with an increased coefficient of friction as V is increased. The addition of V also greatly affected the microstructural orientation of the HEA, exhibiting signs of homogenization as V content increased.
... However, the introduction of secondary elements may result in the formation of several undesired phases, such as intermetallic compounds, which may render the alloys brittle. 12 With the emergence of new technologies in aerospace, electronics, communication, and aviation sectors, there is a growing demand for alloy properties that surpass the capabilities of CAs. 13−16 Owing to their superior intrinsic properties, ongoing research has focused on the development of HEAs with optimized strength. ...
Previously, refractory high-entropy alloys (HEAs) with high crystallinity were synthesized using a configurable target without heat treatment. This study builds upon prior investigations to develop nonrefractory elemental HEAs with low crystallinity using a novel target system. Different targets with various elemental compositions, i.e., Co20Cr20Ni20Mn20Mo20 (target 1), Co30Cr15Ni25Mn15Mo15 (target 2), and Co15Cr25Cu20Mn20Ni20 (target 3), are designed to modify the phase structure. The elemental composition is varied to ensure face-centered cubic (FCC) or body-centered cubic (BCC) phase stabilization. In target 1, the FCC and BCC phases coexist, whereas targets 2 and 3 are characterized by a single FCC phase. Thin films based on targets 1 and 2 exhibit crystalline phases followed by annealing, as indicated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. In contrast, target 3 yields crystalline thin films without any heat treatment. The thin-film coatings are classified based on the atomic size difference (δ). The δ value for the target with the elemental composition CoCrMoMnNi is 9.7, i.e., ≥6.6, corresponding to an HEA with an amorphous phase. However, the annealed thin film is considered a multiprincipal elemental alloy. In contrast, δ for the CoCrCuMnNi HEA is 5, i.e., ≤6.6, upon the substitution of Mo with Cu, and a solid solution phase is formed without any heat treatment. Thus, the degree of crystallinity can be controlled through heat treatment and the manipulation of δ in the absence of heat treatment. The XRD results clarify the crystallinity and phase structure, indicating the presence of FCC or a combination of FCC and BCC phases. The outcomes are consistent with those obtained through the analysis of the valence electron concentration based on X-ray photoelectron spectroscopy. Furthermore, a selected area electron diffraction analysis confirms the presence of both amorphous and crystalline structures in the HEA thin films. Additionally, phase evolution and segregation are observed at 500 °C.
... (d) A schematic of conventional a ball milling device. [14] Reprinted (adopted) with permission from [14] copyright (2019) Springer Nature. (e) An outline of the One-Pot Synthesis of Inorganic nanoparticles using in situ formed metal-oleylamides (X-type ligation). ...
... (d) A schematic of conventional a ball milling device. [14] Reprinted (adopted) with permission from [14] copyright (2019) Springer Nature. (e) An outline of the One-Pot Synthesis of Inorganic nanoparticles using in situ formed metal-oleylamides (X-type ligation). ...
... Ball milling, as shown in Figure 2(d), involves the use of ceramic balls to provide mechanical impact upon milling or grinding to a solvent containing the liquid metal alloy. [14] The special mechanochemistry enables the on-demand transformation of the liquid metal into a low-surface-tension liquid, semi-solid paste, or even solid powder through the use of simple ball milling. [26] Potential contamination of the alloys due to the dissolution of equipment components during the ball milling process could be of concern but ultimately depends on the material composition of the equipment. ...
Significant progress has been made in recent years in the development of liquid metal alloy catalysts. This article provides an overview of the state‐of‐the‐art research pertaining to liquid metal alloy catalysis, including alloy synthesis, reactor design, and theoretical calculations. Different alloy synthesis methods are discussed with a focus on strategies that can achieve colloidal intermetallic structures in liquid metal alloys. Current reactors for liquid metal‐based electrocatalytic and thermochemical processes are summarized. The application of theoretical tools, such as machine learning and computational chemistry to further liquid metal alloy design, is discussed. Finally, an outlook on the technological challenges and our perspective on future research opportunities for liquid metal alloy catalysis are presented.
... There are several methods of synthesizing high-entropy alloys (HEAs), including powder metallurgy, laser cladding, electrodeposition, arc melting, and mechanical alloying [9]. Each of these methods has its advantages and disadvantages, and the choice of method depends on the specific requirements of the application and the properties of the desired alloy [10]. ...
Failure of materials such as steels during engineering applications can result in economic harm; hence, developing new corrosion-resistant materials is critical. In this work, high-grade powders of Al, Cr, Fe, Mn, and Ni were used to synthesize an equimolar AlCrFeNiMn high-entropy alloy (HEA) for potential chemical industry application. The cast alloy's properties were further altered by the addition of 1at%, 3at%, and 5at% tin (Sn) as alloying additives. To assess the impact of Sn on the alloy's resistance to corrosion, potentiodynamic polarization tests were conducted in various acidic and basic environments. Several surface inspection techniques, including scanning electron microscopy (SEM), optical microscopy (OPM), X-ray diffractrometry (XRD), and energy-dispersive X-ray spectroscopy (EDS), were employed to examine the morphological changes and elemental composition of the alloy after it was subjected to corrosive conditions. The nano-indentation machine was used to analyze the materials' nanohardness. TGA analysis was also performed to determine how Sn additions affected the AlCrFeNiMn HEA’s thermal stability. In 0.5 M HCl solution, the Sn-doped alloys demonstrated good corrosion resistance. Their exposure to 0.5 mol/L H 2 SO 4 solution, on the other hand, found to be deleterious to their electrochemical stability. The weight loss of 5 at% Sn-doped samples in 0.5 M H 2 SO 4 solution was found to be substantially reduced. The mass of all the samples stayed constant in 3.5 wt% NaOH solution.
... CoCrFeNi-series HEAs contain no or considerably low concentrations of crack-sensitive elements (such as C and Si), which enables excellent forming ability during AM [7][8][9]. In addition, CoCrFeNi HEAs are suitable for a wide range of applications because their high-temperature resistance, corrosion resistance, and mechanical properties can be effectively tuned by modifying the alloy composition [10][11][12]. For example, Li et al. showed that Fe 50 Mn 30 Co 10 Cr 10 HEAs with a dual-phase microstructure exhibited an outstanding trade-off between strength and ductility when their grain size was refined to 4.5 µm [13]. ...
The microstructural evolution, pitting performance, and passive-film properties of AlxCoCrFeNi high-entropy alloys (HEAs) fabricated via laser melting deposition (LMD) were investigated using material characterization techniques and electrochemical measurements. The substrates of the LMD HEAs transform from a face-centred cubic (FCC) to a body-centred cubic (BCC) structure with increasing Al addition. The BCC-structured B2 and A2 phases precipitate in the HEA substrate when the Al content reaches 10 mol.%. Ternary-phase HEA with Al addition of 10 mol.% exhibits the best corrosion resistance, which is attributed to favourable modifications in the Cr2O3 content and passive-film thickness.
... 4 However, it is still important to consider the results of various manufacturing processes because the properties of HEAs are highly dependent on the processing route. 7 Most of these techniques require high temperatures, material usage, cost, and processing time and cause inhomogeneity. 7 However, thin film synthesis through RF magnetron sputtering can be considered a feasible method for realizing coating on various substrates and applications in extremely harsh environments such as radiations, the aerospace industry, and cutting instruments. ...
... 7 Most of these techniques require high temperatures, material usage, cost, and processing time and cause inhomogeneity. 7 However, thin film synthesis through RF magnetron sputtering can be considered a feasible method for realizing coating on various substrates and applications in extremely harsh environments such as radiations, the aerospace industry, and cutting instruments. 4 Researchers from the materials science community have struggled to develop bioengineered alloys that can bridge the gap of the limitations caused by some of the prominent bioimplants, which cause severe allergic and adverse effects, causing ultimate failure and inflammations. ...
This study presents a novel synthesis route for high-entropy alloys (HEAs) and high-entropy metallic glass (HEMG) using radio frequency (RF) magnetron sputtering and controlling the HEA phase selection according to atomic size difference (δ) and film thickness. The preparation of HEAs using sputtering requires either multitargets or the preparation of a target containing at least five distinct elements. In developing HEA-preparation techniques, the emergence of a novel sputtering target system is promising to prepare a wide range of HEAs. A new HEA-preparation technique is developed to avoid multitargets and configure the target elements with the required components in a single target system. Because of a customizable target facility, initially, a TiZrNbMoTaCr target emerged with an amorphous phase owing to a high δ value of 7.6, which was followed by a solid solution (SS) by lowering the δ value to 5 (≤6.6). Thus, this system was tested for the first time to prepare TiZrNbMoTa HEA and TiZrNbMoTa HEMG via RF magnetron sputtering. Both films were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy cross-sectional thickness, and atomic force microscopy (AFM). Furthermore, HEMG showed higher hardness 10.3 (±0.17) GPa, modulus 186 (±7) GPa, elastic deformation (0.055) and plastic deformation (0.032 GPa), smooth surface, lower corrosion current density (Icorr), and robust cell viability compared to CP-Ti and HEA. XRD analysis of the film showed SS with a body-centered cubic (BCC) structure with (110) as the preferred orientation. The valence electron concentration [VEC = 4.8 (<6.87)] also confirmed the BCC structure. Furthermore, the morphology of the thin film was analyzed through AFM, revealing a smooth surface for HEMG. Inclusively, the concept of configurational entropy (ΔSmix) is applied and the crystalline phase is achieved at room temperature, optimizing the processing by avoiding further furnace usage.
... Since the fabrication route plays a crucial role in the microstructure, mechanical alloying (MA) is a promising route to produce HEAs with better control of the microstructure and uniform dispersion of reinforcement NPs compared to conventional methods. Further consolidation by SPS is a potential route to attain high-density HEAs via controlled sintering temperatures and pressures in short intervals of time [16][17][18][19]. For example, Rogal et al. [20] developed CoCrFeMnNi/SiC composites by MA and hot isostatic pressing (HIP), resulting in a significant improvement of the compressive yield strength from 1180 to 1480 MPa. ...
In this study, TiC-reinforced CoCrFeMnNi high-entropy alloy (HEA) composites were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The phase composition, microstructure, mechanical and thermal expansion behaviour of composite HEAs were investigated. The results reveal that the addition of TiC has no effect on the crystal structure, however, the microstructure and mechanical properties show a strong dependency on the TiC content. Compared to the original HEA, the composite HEA shows decreased grain size, resulting in TiC nanoparticles (NPs) retarding grain growth by pinning the grain boundaries. With increasing TiC content from 0 to 4 wt-%, significant increases in the hardness from 410 to 480 HV and compressive yield strength from 680 to 1100 MPa, which is mainly due to the grain boundary and dispersion strengthening effects. Moreover, the thermal expansion curves show linear increments up to 800°C and decrease with increasing TiC content.
... The most prevalent consolidation processes for HEA powders are vacuum hot pressing sintering and spark plasma sintering. Figure 6 depicted the different sintering stages such as,(a) bonding points at particles linked to each other (b) Necks produced bonding points (c) holes between grain boundaries shrink, and (d) boundaries expand between particles [1]. Because of alterations in the microstructural phases, LPS is not encouraged in HEAs [15].The sintering process is categorized into three stages: heating, holding, and cooling. ...
... HEA solid-state processing approaches [Powder atomization process[1,8] ...
... (a) Jar for Grinding (b) High Energy Ball Milling Schematic[1] ...
... The surface area of the solid material can be increased appreciatively using ball milling, even the desired size of grain can be obtained using this method. 49,50 The advantages of the ball milling technology include the ability to produce extremely small particle sizes and operate continuously. However, there are significant drawbacks including high machine noise levels, the potential for contamination brought on by the system's used balls wearing out over time, and occasionally lengthy grinding times. ...
With the advancement and up-gradation of wireless technology, people worldwide are surrounded by microwaves, however, with the brighter side comes the darker side too. These microwave/electromagnetic wireless signals interfere with the environment/mankind and are referred to as electromagnetic interference (EMI)/electromagnetic or microwave pollution. Microwave/electromagnetic absorbers are used to mitigate this EMI or electromagnetic pollution. Researchers have been working on microwave absorbents of different kinds to save humans, their gadgets, electronically printed cards, etc. to create a healthy and radiation-free environment. Recently, there is an advancement in different forms of ferrite absorbers. This review presents a description of what are ferrite-based microwave absorbers, the preparation method of absorbers, the working principle, and detailed insights involving necessary models and mechanisms regarding microwave absorption. It also encapsulates the description of how the ferrite composition, morphology, doping, reflection loss peaks, and matrix account for optimizing the performance of the absorbers. The history, origin, and ancestral use of microwave absorbers are mentioned, and how technological needs lead to advancement in ferrite microwave absorbers has also been discussed. A picture is portrayed of what are microwaves, their potential hazards, and how these hazards should be taken care of with the help of ferrite microwave absorbers.
... Most of the research on the Al-Cu alloy system is centered around Al-4Cu wt%, as this composition represents a typical age-hardening system. Because of their high strength-to-weight ratio, these aluminium alloys are frequently employed in industrial applications [7,8]. Increasing the copper content enhances strength in both as-cast and heat-treated conditions. ...
Laser-based powder-bed fusion (LPBF) / Selective laser melting (SLM) was used to fabricate a eutectic composition of Al-33Cu alloys in-situ. Different scan strategies (1×1, 2×2, 3×3, 4×4, and 60°) were adopted to understand its effect on porosity, phase formation, microstructural and texture evolution, and mechanical properties. The 1×1 specimen showed the highest porosity among the hatch variation, and the 60° scan strategy showed the least. X-ray diffraction from the specimens prepared using different scan strategies showed a mixture of Al (face-centered cubic) and Al2Cu (body-centered tetragonal) phases. The microstructure of all the specimens revealed eutectic lamellar-type morphology; however, the interlamellar spacing was observed to be different at the melt and laser track-overlapped regions. The nano-lamellar eutectic microstructure exhibited a compressive strength exceeding 1 GPa. Nano-indentation in two distinct regions indicated an Al-rich softer zone and an Al2Cu rich harder zone. Bulk texture analysis was also done for both phases for all the hatch-varied specimens, and it shows a particular texture component intensifies from weak fiber as the scan strategy is altered.
