NiAl Phase Research Articles

Development of a bilayer NiCrAlY/YSZ coating on IN713 LC superalloy by laser cladding

In this study, bilayer laser cladding of Inconel 713LC superalloy was performed by a Nd:YAG laser. Amdry 997 powder was used as the first layer and Metco 204NS ceramic powder as the second layer. The experiments were carried out with different laser parameters to investigate the influence of heat input and laser power density on the microstructure and the hardness of coating. The study revealed that the susceptibility to crack formation in the clad zone increases with the increase in the heat input due to the high cooling rate and intense thermal stress. The formation of shrinkage cavities in the lower half of the clad zone raises with the increase in the heat input owing to reduction in the solidification rate. Microstructural investigations show that a cellular structure is formed at the interface region. The middle area of coating features columnar dendrites, while the upper area of the coating displays very small equiaxed dendrites. The coating mainly comprises γ-Ni, β-NiAl and γ′-Ni3Al phases and the elements of Ni, Co, Cr, Al, Ta, Zr, and Y are homogeneously distributed in the clad zone. As the heat input increases, the microhardness of the samples decreases due to an increase in the dilution ratio. This leads to a decrease of Co, Cr, and Ta elements in the γ′ and the β intermetallic compounds, as well as a reduction of Zr and Y elements in the clad zone.

Microstructure, mechanical properties and multiphase synergistic strengthening mechanisms of a novel laser additive manufactured AlNi6TiZr alloy

In this work, selective laser melting (SLM) process is used to prepare the AlNi6TiZr alloy. By analyzing the printing quality and mechanical properties of the printed specimens with different process parameters, the SLM forming window of AlNi6TiZr is obtained. The relative density of the sample printed with 270 W-1100 mm/s (laser energy density: 82 J/mm3) reaches 99.7%, exhibiting excellent mechanical properties (yield strength (YS): 421.7 MPa; ultimate tensile strength (UTS): 480.4 MPa). After an aging treatment of 325 °C-12 h, the YS and UTS of the sample increased to 494 MPa and 550.7 MPa, respectively. Adding Ni, Ti, and Zr components promoted the generation of multi-phase precipitates in the Al alloy and improved the synergistic strengthening effect of multi-phases. The hard-shell structure (HSS) formed by the Al3Ni phase at the grain boundary significantly strengthened the grain boundary strength. The precipitated Al3(Ti, Zr) phases at the grain boundaries prevent grain growth and dislocation movement. The Al3Ni and Al3(Ti, Zr) phases have good thermal stability that can still maintain excellent enhancement effects at high temperature. AlNi6TiZr alloy has great application prospects in medium and high-temperature environments.

Microstructural evolution and elemental interdiffusion behaviour near the interface of NiAlTa alloy and single crystal superalloy DD5 at 1000 °C, 1050 °C, and 1100 °C

The NiAlTa system has been identified as a possible candidate for a protective coating material for single crystal superalloy blade tips. The microstructural evolution and elemental interdiffusion behaviour of NiAlTa/DD5 diffusion couples at 1000 °C, 1050 °C, and 1100 °C were investigated. Significant elemental interdiffusion occurred between the NiAlTa alloy and DD5 alloy. γ'-Ni3Al, AlNi2Ta, and TCP phases were generated in the NiAlTa/DD5 diffusion couples. Ni had the highest average effective interdiffusion coefficient and the lowest diffusion activation energy, while the opposite was true for Ta. The precipitation of the TCP phase raised the potential for cracking in the substrate.

Ultra-short pulsed laser ablation of decagonal AlCoNi and AlCoCuNi quasicrystals

Al70Co20Ni10 and Al70Co15Cu10Ni5 (at%) decagonal quasicrystals (DQCs) were subjected to femtosecond laser ablation at a laser wavelength of 800 nm, in deionized water (DI). The generated nanoparticles (NPs) confined within the liquid medium were studied for optical and structural properties. The structural analysis revealed the retention of the targets phase in the NPs. In case of Al70Co20Ni10, formation of Al3Ni2 phase was confirmed through the SAED patterns and HRTEM micrographs. Contrary to this, the formation of Al-Ni phase was not observed in Al70Co15Cu10Ni5. This is attributed to the presence of Cu in the latter sample, which restricts the mixing of Ni with Al. The HRTEM micrographs in both cases showed that Al2O3 was present at the edges of the NPs. The optical analysis confirmed the formation of Al2O3 in both cases. However, in the case of Al70Co15Cu10Ni5, a very weak signal corresponding to CuO was detected. This is attributed to the diffusion of Cu along with Al at the edge. The ablated region of the target’s surface was studied for the formation of laser-induced periodic surface structures (LIPSS) also known as ripples, and the type of ripples formed was identified.

Influences of Cu on microstructure and mechanical properties in Fe–Ni–Al ultra-strong maraging steels

Although the influences of Cu on microstructure and mechanical properties have been extensively studied in low-alloy steels, the aging behavior of high-alloy maraging steels with Cu remains elusive. In this work, we systematically investigated the nanoprecipitation behavior and their effects on mechanical properties in Fe–Ni–Al ultra-strong maraging steels by introducing different amounts of Cu. Structural analyses with atom probe tomography (APT), transmission electron microscopy (TEM) and small angle neutron scattering (SANS) indicate that the addition of Cu promotes the precipitation of nanoscale B2–NiAl phases in the Fe–Ni–Al ultra-strong maraging steels. The primarily precipitated Cu-clusters can serve as the nucleation sites for the precipitation of B2–NiAl at the early stage of aging, and then are dissolved into the B2–NiAl nanoprecipitates, which increases the lattice misfit between the B2–NiAl and the matrix and thereby the growth rate of B2–NiAl. As a result, the addition of 0.6 wt% Cu significantly improves the ductility of the Fe–Ni–Al ultra-strong steel without sacrificing strength. With 0.6 wt% Cu added to the Fe–Ni–Al ultra-strong steel, the elongation increased from 3.2% to 8.7% while the strength remained 2.0 GPa, due to the high-density precipitation of Ni(Al, Cu) nanoparticles. The underlying mechanisms for the precipitation behavior and the precipitation strengthening effect were discussed in terms of lattice misfit, Cu segregation and stress field.

Chemical reactions of Ni/Al multilayers upon ultrahigh compressive load at ambient temperature

Energetic multilayers are peculiarized by their self-propagation reactions when giving them a thermal pulse. This work reports the chemical reactions of Ni/Al energetic multilayers can be triggered upon ultrahigh compressive load (stress >1 GPa) at ambient temperature, which is realized by micro-compressions of Ni/Al micropillars with equal molar ratio. Detailed microscopic characterizations evidence monolayer reactions of Ni20Al30 and Ni110Al140 (NixAly: x and y are average thickness of individual layers in nanometer) are triggered, forming a stoichiometric NiAl phase after micropillar compression. The as-observed reactions must be triggered by ultrahigh compressive loads, which aid for nucleation of NiAl grains at atomic intermixing zones of Ni-Al interfaces. Once occurrence, the grain growth is self-sustained by the released heat during NiAl formation. The grain textures depend strongly on the deformation extent. The self-sustained process is terminated until the whole micropillar is reacted. Analogous chemical reactions are not observed in the thickest Ni450Al620 micropillar where atomic intermixing is absent. The comparison highlights the critical role of ultrahigh compressive load to trigger monolayer reactions of Ni/Al multilayers, and could forward the advance of Ni/Al energetic multilayers for diffusion welding purpose.

The influence of Ni on the contributions of the superplastic deformation mechanisms of the Al–Zn–Mg–Cr alloys

The Ni influence on the superplastic characteristics, the microstructure evolution and the contributions of the superplastic deformation mechanisms for Al-Zn-Mg-Cr-based alloys have been investigated. The alloys contained dispersoids enriched with Cr, Mg and a minor of Zn of a mean size of 140 nm and in addition the Al3Ni phase in the alloy with nickel. Al3Ni phase increased homogeneity and stablity grain structure during elevated annealing temperature and during superplastic deformation at 440°C. The mean grain size decreases from 7.7 to 7.3 µm before the onset of the deformation and from 10 to 8.6 µm after straining of 0.69. The dislocations aggregations near Al3Ni particles were revealed. The microstructure evolution was compared at the testing condition providing a similar value of the strain rate sensitivity coefficient m≈0.6. The grain boundary sliding contribution is twofold larger and the intragranular dislocation slip is three times smaller in the alloy with Al3Ni particles compared to nickel-free alloy. Al3Ni particles leads to more equiaxed finegrain structure and an increase elongation to failure.

Investigation of the ordered and disordered corrosion morphologies on Ni-based alloy in the passive state

We report an order and disorder combined corrosion morphology of dual-phase Ni-based alloy in the passive state. After galvanostatic polarization in the passive region, the surface of the γ(Ni) phase presents amorphous feature while that of the γ′(Ni3Al) phase maintains crystalline. The variations in weight percentages of Ni (50.19% → 3.80%), Co (19.24% → 0.65%), Ta (0.85% → 21.19%), and W (5.73% → 43.79%) of γ surface are evident, whereas the composition of γ′ surface is nearly unchanged. The passive film comprises Wox6+, Taox5+, Crox3+, Coox8/3+, Nihy2+, and Cohy2+, and it shows stronger protection effect on the γ phase.

Diffusion bonding of FGH98 superalloy and DD5 single crystal using pure Ni interlayer

In this study, the FGH98 superalloy and DD5 single crystal were diffusion bonded using pure Ni interlayer under the pressure of 4 MPa. The elemental interdiffusion of Ni interlayer and base materials induced Ni3Al phases (γ’) reinforced Ni-based solid solution (γ) bonding seam (Ni layer zone), achieving the reliable joining of FGH98 and DD5. With the increase of diffusion bonding temperature, the elemental interdiffusion was promoted significantly, which was beneficial to the formation of γ’ phase in the joint. Due to the formation and enlargement of γ’ phase, the hardness of the Ni layer zone and the joint shear strength raised. The high diffusion bonding temperature (1160 ℃) resulted in γ’ phase bulk in the Ni layer zone, and the maximum joint strength of 630 MPa was achieved. However, the fracture of the joint obtained at 1160 ℃ was located in the Ni layer zone.

Effect of Al content in the pyrotechnic mixture on the properties of the BaAl2O4-based composite coating deposited on steel by a novel explosive spray technique

A low explosive material such as pyrotechnic mixture made of Al and Ba(NO3)2 powders, commonly known as the flash powder, is used to deposit BaAl2O4-based composite coatings on a flat mild steel surface by using a novel explosive coating setup developed in the laboratory. To achieve the high tribo-mechanical properties of the deposited coating, a suitable mixing ratio of Al to Ba(NO3)2 is to be found. In this work, the Al content of the flash powder is varied from 1 to 2.5 gm for 2 gm of Ba(NO3)2 to study the effect of Al content on the properties of the deposited BaAl2O4-based coatings. The fabricated coatings are characterized in terms of thickness, crystalline phase, microstructure, surface roughness, hardness, and wear resistance by using an optical microscope, X-ray diffractometer (XRD), Field emission scanning electron microscope (FESEM), stylus profilometer, Vickers micro-hardness tester, and linear reciprocating wear tester respectively. Up to 2 gm of Al addition, the hardness of the coatings is found to be enhanced remarkably. However, with further addition of Al, it is found to be decreased significantly. With 2 g of Al content, the major portion of Al powder is utilized well in the chemical reaction to produce mainly hard BaAl2O4 and AlN phases. The highest amount of energy is released from such a composition of feedstock. The presence of pure Ba and Al in the coatings from 1 g to 1.5 g of Al, respectively, have helped to enhance the wear resistance of those by reducing the coefficient of friction values. However, the high wear resistance obtained for the coating obtained from 2 g of Al content is due to the major presence of hard phases and low porosity in it. On the other hand, the high porosity and the major presence of partially melted pure Al particles make the coating from 2.5 g of Al less wear resistant. From a 1:1 mixing ratio of Ba(NO3)2 to Al powders in the flash powder, a hard and monolithic BaAl2O4-based composite coating with minimum defects can be obtained.

Fe-14Ni-14Cr-2.5Al steel showing excellent corrosion-resistance in flowing LBE at 550 °C and high temperature strength

We investigated the corrosion behavior, microstructural evolutions, and mechanical properties in an alumina forming austenitic (AFA) Fe-14Ni-14Cr-2.5Al steel after exposure in the flowing lead-bismuth eutectic (LBE) at 550 °C for 4008 h and aging in air for 5000 h. The results showed that the AFA steel exhibited not only excellent corrosion-resistance in the flowing LBE but also a strong stability of austenite and high yield strength (589 MPa) at 550 °C. The excellent corrosion-resistance was ascribed to the rapid formation of a thin Al2O3 scale. For the first time, the precipitation of γ'-Ni3Al phase was observed in the AFA steel after long-term aging at 550 °C.

Peridynamics study on crack propagation and failure behavior in Ni/Ni3Al bi-material structure

In this paper, the crack propagation and failure behavior of Ni/Ni3Al bi-material structure are investigated under the framework of peridynamics (PD). The effects of the location of the pre-crack, the loading rate, and the interface setting of the bi-material structure on the crack propagation path and propagation rate are discussed. The numerical results show that PD method can effectively simulate the whole process of crack propagation and failure characteristics in Ni/Ni3Al bi-material with an interface, and the accuracy of the results is verified by the finite element method. The crack propagation path and failure characteristics strongly depend on the initial location of the pre-crack. Three different crack propagation paths and failure characteristics are found when pre-crack in the Ni phase, Ni3Al phase, and the Ni/Ni3Al interface, respectively. The numerical results also find the interface setting has a significant impact on the crack propagation, when the interface setting with harmonic mean is more capable of hindering crack propagation and reducing crack propagation rate. The present work provides an important reference for the crack propagation and failure of Ni/Ni3Al idealized superalloy and other composites containing complex interfaces.

Particle Stimulated Nucleation Effect for Al-Mg-Zr-Sc Alloys with Ni Addition during Multidirectional Forging

The study aims to investigate the influence of fraction of coarse undeformed particles on the microstructure evolution and mechanical properties of alloys processed by isothermal multidirectional forging (MDF). For this purpose, Al-Mg-Ni-Sc-Zr-based alloys with different Ni concentrations and a fraction of Al3Ni particles of solidification origin phase were subjected to MDF at 350 °C. Precipitates of the L12-structured Al3(Sc,Zr) phase retained their structure, morphology, and size after MDF and were coherent with the aluminum matrix. The Al3Ni phase particles stimulated the nucleation of recrystallized grains and contributed significantly to the formation of an ultrafine-grained structure. The uniformity of the grain structure increased, and the average grain size decreased with an increase in the fraction of Al3Ni particles. A fine-grained structure with a mean grain size of 2.4–3.4 µm was observed after MDF with a cumulative strain of 12. The results demonstrate that a bimodal particles size distribution with a volume fraction of nanoscale f~0.1% and microscale f~8% particles provided for the formation of a homogenous fine-grained structure after MDF and improved the mechanical properties.

A novel ODS high-entropy composite with improved strength and ductility

Body-centered cubic (BCC) structured high-entropy alloys (HEAs) usually exhibit excellent strength, thermal stability, irradiation tolerance and corrosion resistance but low ductility. In this study, a novel oxide dispersion strengthened (ODS) AlCrFeNi high entropy composite (with BCC-structure reinforced by face-centered cubic (FCC) ODS-CoCrFeNiMn HEA reinforcement was designed and prepared by mechanical alloying and spark plasma sintering. The effects of sintering temperatures (950 °C, 1000 °C, 1050 °C and 1100 °C) and reinforcement amount (5%, 10%,15% and 20%) on microstructure and mechanical properties were investigated. The results showed that the optimal sintering temperature of the ODS AlCrFeNi composites is 1100 °C. The hardness decreases with the increase of the reinforcement content (from 5% to 20%). Compared to the reference alloy (RA) without the addition of reinforcement, the compressive strain of the composite with 15% reinforcement (B–15%F) increases significantly from 8% (RA) to 18%, while the compressive strength increases from 2823 MPa (RA) to 3078 MPa. The B–15%F is composed of matrix, reinforcement and intermediate transition regions. The thickness of transition regions increases with increasing sintering temperature. The matrix consists of fine BCC FeCr phase and B2 NiAl phase, due to spinodal decomposition, together with high-density nanoscale oxides Y4Zr3O12 and a small amount of Y–Al–O. Surprisingly, the crystal structure of reinforcement transforms from FCC into the BCC during SPS. Meanwhile, the mutual diffusion of Al elements in the matrix and Co and Mn elements in the reinforcement also results in similar spinodal decomposition in the reinforcement. The domain size of spinodal decomposition in the reinforcement is coarser than that in the matrix. The reinforcement is mainly distributed on the prior particle boundaries (PPBs), which can effectively reduce/suppress the formation and propagation of micro-cracks along the PPBs, and thus improve both the strength and ductility of the composite.

Characteristic and tribological behavior of amorphous carbon–containing CrAlCN coating by cathodic arc ion plating

Amorphous carbon–containing CrAlCN coating was deposited on Cr12MoV steel by cathodic arc ion plating. The effect of amorphous carbon on the tribological performance of obtained coating under the different normal loads was investigated using a ball–on–disc tester, and the lubrication and wear mechanisms of amorphous carbon were discussed in detail. The results show that the CrAlCN coating is composed of AlN, CrN and CrC phases with the amorphous carbon. The average coefficient of friction of CrAlCN coatings under the normal loads of 2, 4 and 6 N are 0.458, 0.586, and 0.666, respectively, where the amorphous carbon plays a self–lubrication role in the friction process. The wear degree is deteriorated with the increase of normal load, and the wear mechanism is changed from abrasive wear to adhesive wear.

XPS and dielectric studies of phase pure AlN-BN composite ceramics using powder bed

In this study, AlN-BN composite ceramics have been sintered with a powder bed in the conventional sintering method at 1700 °C for 20 h in the presence of nitrogen. The XPS studies reveal the pure phase formation of the AlN-BN composite, and the presence of oxygen is only at the sample's surface. The obtained composites exhibit pure wurtzite AlN phase without any oxide phases as secondary phases. The temperature dependent Raman spectra show six vibrational modes of wurtzite structure at every temperature. The best dielectric properties (εr = 6.50–7.48) with (tanδ = 0.2 × 10−3–9.8 × 10−3) are achieved for AlN-15BN composite ceramics by varying temperatures from 30 to 500 °C, with frequency variation from 1 kHz to 1 MHz. Impedance spectra of AlN-BN composite ceramics are appropriately fitted with the equivalent circuit consisting of RCRCRC for all the sintered samples. The best microwave dielectric properties as εr = 7.381 and tanδ = 2.603 × 10−3 achieved are appropriate for RF-window and electronic applications.

Vacuum diffusion bonding between Ni3Al-based superalloy and S31042 steel by surface self-nanocrystallization treatment

Vacuum diffusion bonding at a relatively low temperature is a recognized method for restraining intermetallics and optimizing joint microstructure. The surface self-nanocrystallization (SSN) treatment by shot peening technology is applied on the surface before bonding a couple of Ni3Al-based superalloy and S31042 steel, which lowers the bonding temperature for achieving a sound joint by 100 °C. Moreover, the joint strength of samples bonding at 1000 °C after SSN treatment is 178 MPa higher than that of the bonded samples at 1100 °C without SSN treatment. SEM, XRD and TEM analyses indicate SSN treatment improves bonding efficiency by increasing surface micro-deformation and introducing nanocrystalline and deformed layer. The formation of disordered Ni-solution on the surface makes γ’ strengthening phase re-precipitates in the joint and hard-brittle phase of AlN is restrained by diffusion bonding at 1000 °C. The good metallurgical bonding, re-precipitated γ’ phase and the formation of refining grains zone near the bonding interface contribute to the good performance of 1000 °C-bonded samples after SSN treatment.

Effect of sub-solvus treatment on discontinuous precipitation behavior and mechanical properties of AlCrFeNiV multi-principal element alloy

The discontinuous precipitation (DP) behavior of AlCrFeNiV multi-principal element alloys (MPEAs) based on initial face-centered-cubic (FCC) single-phase structure is investigated in this work. The investigation focuses on the impact of a novel sub-solvus (SS) treatment, which accelerates the DP transformation kinetics by refining the microstructure, as compared to the conventional total-solution (TS) treatment. This acceleration is attributed to an increase in nucleation sites or localized changes in chemical composition. The presence of NiAl phases with a B2 structure, which precipitate along prior grain boundaries, is believed to play a dominant role in grain refinement. Additionally, highly dispersed L12 nano-precipitates are observed within the FCC matrix in both TS- and SS-treated samples. Building upon the strengthening effect of L12 nanoprecipitates, further optimization strategies are explored through variations in isothermal aging treatments. This leads to the preparation of DP structures with various degrees and morphologies, consisting of BCC phases and a coherent FCC/L12 microstructure. The additional HDI hardening stemming from the resulting DP/non-DP heterogeneous structure and the spheroidization of the ultrafine DP lamellar structure allowed the alloy to exhibit excellent mechanical properties, the latter of which yielded an interesting combination of strength (1907 MPa tensile strength, 1694 MPa yield strength) and ductility (10.1% elongation). These findings highlight the effect of the prior grain refinement on the DP transition kinetics, BCC lamellae stability, and the overall mechanical performance of AlCrFeNiV multi-principal element alloys (MPEAs).

Ni-catalyzed carbon–carbon bonds cleavage of mixed polyolefin plastics waste

The inert carbon–carbon (C–C) bonds cleavage is a main bottleneck in the chemical upcycling of recalcitrant polyolefin plastics waste. Here we develop an efficient strategy to catalyze the complete cleavage of C–C bonds in mixed polyolefin plastics over non-noble metal catalysts under mild conditions. The nickel-based catalyst involving Ni2Al3 phase enables the direct transformation of mixed polyolefin plastics into natural gas, and the gas carbon yield reaches up to 89.6%. Reaction pathway investigation reveals that natural gas comes from the stepwise catalytic cleavage of C–C bonds in polypropylene, and the catalyst prefers catalytic cleavage of terminal C–C bond in the side-chain with the low energy barrier. Additionally, our developed approach is evaluated by the technical economic analysis for an economically competitive production process.

Mathematical modeling of hydrogen production performance in thermocatalytic reactor based on the intermetallic phase of Ni3Al

Mathematical modeling of hydrogen production performance in thermocatalytic reactor based on the intermetallic phase of Ni3Al