Semi-coherent Interface Research Articles

Coherent to semi-coherent transition of precipitates in Van der Merwe epitaxial films

Abstract The interplay of stresses of two coherent systems, specifically a coherent precipitate within an epitaxial film (in Van der Merve growth mode), gives rise to an interesting scenario; wherein the configurational effects and the strain energy landscape are enriched. This leads to an interdependent evolutionary pathway for the coherent to semi-coherent transition. The transition of the film-substrate interface to the semi-coherent state occurs beyond a critical thickness ( t c ) which arises from energy minimization. Using the model example of the precipitation of NbH0.5 precipitate in a Nb/Sapphire epitaxial system, the critical radii ( r film ∗ ) for model geometries have been computed. 3D finite element models have been used to compute the stress state and energetics of precipitates growing in an epitaxial film. The following important observations can be made based on the simulations. (1) The epitaxial stresses can lead to the stabilization of the coherent precipitate. (2) The transition to a semi-coherent film interface, characterized by an array of interfacial misfit dislocations, can energetically favor the semi-coherent state of the precipitate over the coherent state. The magnitude of r film ∗ depends on the spatial coordinates within the film. (3) The presence of Nb–H coherent precipitates can stabilize the coherent state of the film interface.

Laser powder bed fusion in-situ alloying of W-Y alloy: Microstructure, mechanical properties and cracking suppression

The microcracks caused by impurity oxygen are recognized as one of the main challenges in additive manufacturing of tungsten. In this study, yttrium was incorporated into the tungsten matrix to suppress crack formation, and W-Y alloys with minimal cracks were successfully obtained by laser powder bed fusion (LPBF). It is found that during the LPBF process, yttrium combines with impurity oxygen to generate intergranular and intragranular precipitated particles in situ, which effectively suppress cracking behavior due to impurity oxygen. Furthermore, these intracrystalline nanoprecipitate are cubic Y2O3 particles that have formed a semi-coherent interface with the tungsten matrix. These dispersed particles significantly improved the mechanical properties of W-Y alloy. The results offer a corresponding strategy for crack suppression of tungsten alloys in laser additive manufacturing processes, and would provide a benificial additive manufacturing strategy to other refractory alloys.

The many faces of θ'-Al2Cu precipitates: Energetics of pristine and solute segregated Al/θ' semi-coherent interfaces

θ'-Al2Cu precipitates in Al-Cu alloys have various distorted octagon shapes, which can be explained by the competition between {100} and {110} type semi-coherent interfaces with the Al matrix. While most prior studies on the semi-coherent Al/θ' interfaces have focused on the {100} orientation, little is known about the {110} interface. We have investigated the energetics of pristine and solute-segregated {110} semi-coherent Al/θ' interfaces with advanced characterization and first-principles studies. We report interfacial, strain, and solute segregation energetics of the {110} Al/θ' semi-coherent interface for 39 elements and compared them with previously reported values of the {100} interface. We discuss the atomic features and atomic local structures to identify similarities and differences between the two types of Al/θ' semi-coherent interfaces. The isotropy in pristine Al/θ' semi-coherent interfacial energy and the anisotropy resulting from solute segregation provide insight into the formation of different types of θ' precipitate “faces” reported in the literature.

In-situ formed TiCx reinforced Ti composites derived from polyzirconocarbosilane precursor: Synthesis, characterization and mechanical properties

Discontinuously reinforced titanium (Ti) matrix composites (DRTMCs) strengthened by in-situ TiCx particles are synthesized via pyrolysis of polyzirconocarbosilane (PZCS) and pressureless sintering. The Ti matrix reacts with the pyrolysis product of PZCS to form TiCx particles, which effectively refine the α-Ti grains and create a clean, well-bonded semi-coherent interface. A notable orientation relationship is observed between the TiCx and α-Ti phases: (111)TiCx||(101¯1)Ti and [1¯10]TiCx||[12¯10]Ti. The Ti-2PZCS composite demonstrates a significant reduction in average grain size, from 101.5 μm in pure Ti to 39.49 μm, coupled with superior comprehensive mechanical properties: an ultimate tensile strength of 710 MPa, a yield strength of 588 MPa, and an elongation of 9.5 %. The enhanced strength of Ti/PZCS composites is mainly due to grain refinement, solid solution strengthening, and load transfer mechanisms. This study introduces a novel approach for fabricating high-performance Ti composites, highlighting the potential for advanced material applications.

Microstructure and tensile properties of in-situ TiAl nanoparticles reinforced AZ31 composites

The good interfacial bonding between reinforcements and magnesium (Mg) matrix is the essential requirement for the development of magnesium matrix composites (MMCs) with high performance. Herein, this work tries to improve the interfacial bonding of MMCs. Here, the pre-dispersed Ti nanoparticles were introduced in AZ31 composites to form in-situ TiAl nanoparticles, and the AZ31 composites were synthesized by semisolid stirring assisted ultrasonic vibration method. Microstructural analysis reveals that the TiAl nanoparticles are in-situ formed by the Al atoms in composites diffusing into Ti nanoparticles, and the composites obtain a strong interfacial bonding between the TiAl nanoparticles and matrix owing to the formation of TiAl/Mg semi-coherent interface. The composites achieve simultaneous improvement of strength and plasticity. The composite with 0.2 wt% Ti nanoparticles addition possesses the best comprehensive tensile properties. The corresponding ultimate tensile strength and elongation reach 315 MPa and 21.3 %, respectively. The enhanced strength is owing to dislocation strengthening, grain refinement strengthening, and Orowan strengthening. The good plasticity is the result of the activation of non-basal dislocations, refined grains, weakened texture, and good interfacial bonding.

Investigating interfacial segregation of [formula omitted]/Al in Al–Cu alloys: A comprehensive study using density functional theory and machine learning

Solute segregation at the interface between the aluminum (Al) matrix and the Ω (Al2Cu) phase decreases the interfacial energy, impedes the coarsening of precipitates, and enhances the thermal stability of such precipitates. In this study, we employ density functional theory to systematically calculate solute segregation energies of 42 solute elements at the coherent and semi-coherent interfaces between the two phases, as well as mixing energies of these elements within the Al and Cu sublattices of the Ω phase. Using correlation analysis and machine learning methods, we establish the relationship between the solute segregation energy and 20 selected atomic descriptors. Metalloid and late transition metal elements are predicted as potential candidates for enhancing the thermal stability of Al–Cu alloys. We observe that the solute segregation energy at the interfacial site of the semi-coherent interface correlates with the atomic size of solute atoms and their solubilities within the Ω phase. The developed machine learning models exhibit the potential to predict solute segregation energies at various sites of the coherent and semi-coherent interfaces. Overall, our study provides valuable insights into the stabilizing potential of individual elements at the Ω/Al interface in Al–Cu alloys.

Relationship between the superelasticity and strain field around Ni4Ti3 nano-precipitates in NiTi shape memory alloy via laser powder bed fusion

Although the simulation results had demonstrated that the strain field introduced by Ni4Ti3 nano-precipitates in NiTi shape memory alloys (SMAs) was related with their superelasticity inherently, the corresponding experimental result was rarely documented heretofore, especially in additive manufactured NiTi SMAs. In this work, we tailor the morphologies and resultant strain field of Ni4Ti3 nano-precipitates by heat treatment of a NiTi SMA subjected to laser powder bed fusion (LPBF), and further authenticate relationship between the superelasticity and the strain field in the LPBF NiTi samples. When holding times were 1 h, 3 h, and 5 h at aging temperature of 350 °C after solution treatment, the Ni4Ti3 nano-precipitates in the LPBF NiTi samples exhibit spherical, ellipsoidal, and lenticular morphologies, respectively. Accordingly, the strain field around Ni4Ti3 nano-precipitates in B2 matrix decrease from 0.15 % to 0.13 % and 0.10 %, respectively. The LPBF and aged NiTi samples present large superelasticity, which exceeds 6 % recovery strain together with high recovery rate of ˃99 % during 10-times cyclic compression loading. Interestingly, the LPBF and aged sample with the spherical Ni4Ti3 and highest strain field displays the worst superelasticity stability, while the one with the lenticular Ni4Ti3 and smallest strain field exhibits the relatively stable and biggest superelasticity of 6.36 %. Basically, this is attributed to different mechanisms between the Ni4Ti3 nano-precipitates and dislocations generated during cyclic loading, which is induced by different interfaces between the Ni4Ti3 and B2 matrix in the three types of the NiTi samples. For the sample with the highest strain field, its spherical Ni4Ti3 was cut through by generated dislocations due to coherent interface between the spherical Ni4Ti3 and B2 matrix. In contrast, the one with the smallest strain field, its lenticular Ni4Ti3 can impede effectively generated dislocations because of semi-coherent or non-coherent interface between the lenticular Ni4Ti3 and B2 matrix. Therefore, these results can provide meaningful insights into tailoring the nano-precipitates and thereby obtaining excellent superelasticity of NiTi SMAs by LPBF.

(Invited) Operando Nanoimaging of Phase Transformations in Energy Storage Materials

We applied operando Bragg Coherent Diffractive Imaging (BCDI) to study the discontinuous phase transformation in LixNi0.5Mn1.5O4 embedded in a fully operational battery. During Li-intercalation, we observed nucleation and growth of the Li-rich phase in a 500 nm particle embedded in the multicomponent positive electrode. The data captures the evolution from a curved coherent to planar semi-coherent interface, driven by dislocation dynamics. These dislocations travel with the interface and are expelled upon the completion of the phase transformation, resulting in a crystal devoid of defects. We hypothesize that these defects move via glissile motion without diffusion of host ions. Our data indicate the absence of significant kinetic limitations affecting the transformation kinetics, even under rapid discharge within 2 hours. This study underscores the capability of BCDI as a powerful tool for operando analysis of nanoscale phase transformations, offering guidance for the design and optimization of electrochemical materials.

Investigating coherent and semi-coherent interfacial structures and energetics in [formula omitted] interfaces: Theoretical insights into aluminum matrix composites bonding

Understanding the intricate interfacial structures and energetics between ceramics and aluminum is crucial for elucidating the mechanical properties of aluminum matrix composites (AMCs). However, previous theoretical simulations primarily focused on coherent interfaces, neglecting lattice constant variations on heterogeneous interfaces, which has led to discrepancies with experimentally observed semi-coherent interfaces. Here, using recently synthesized Al/Al3BC AMCs as a case study to systematically construct six semi-coherent interfacial models containing 383 to 588 atoms. These models are used to investigate the Al(11¯1)/Al3BC(0001) and Al(3¯11¯)/Al3BC(0001) structures and their associated energetics. Additionally, we examine 39 coherent interfaces for comparison. Work of adhesion and interfacial energy results reveal that the stable termination for semi-coherent interfaces is Al(B), which contrasts with AlC termination observed in coherent interfaces. Both Al(11¯1)/Al3BC(0001) and Al(3¯11¯)/Al3BC(0001) semi-coherent interfaces demonstrate higher stability but lower bonding strength compared to coherent interfaces. Bonding strength and stability of Al(B)-terminated semi-coherent interface in Al(3¯11¯)/Al3BC(0001) are lower than those in Al(11¯1)/Al3BC(0001). Electronic structure analysis indicates that AlC-terminated coherent interface exhibits greater charge transfer and stronger covalent metal bonds, while the Al(B)-terminated semi-coherent interface shows less charge transfer and more pronounced metallic bond characteristics. These computational insights provide valuable theoretical understanding of interfacial bonding mechanisms inherent in ceramic-reinforced AMCs.

Enhanced Thermoelectric Performance of N-Type PbSe Through Semi-Coherent Nanostructure by AgCuTe Alloying.

N-type PbSe thermoelectric materials encounter challenges in improving the power factor due to the single-band structure near the Fermi level, which obstructs typical band convergence. The primary strategy for enhancing the thermoelectric figureof merit (ZT) for n-type PbSe involves reducing lattice thermal conductivity (κlat) by introducing various defect structures. However, lattice mismatches resulting from internal defects within the matrix can diminish carrier mobility, thereby affecting electrical transport properties. In this study, n-type AgCuTe-alloyed PbSe systems achieve a peak ZT value of ≈1.5 at 773 K. Transmission electron microscopy reveals nanoprecipitates of Ag2Te, the room temperature second phase of AgCuTe, within the PbSe matrix. Meanwhile, a unique semi-coherent phase boundary is observed between the PbSe matrix and the Ag2Te nanoprecipitates. This semi-coherent phase interface effectively scatters low-frequency phonons while minimizing damage to carrier mobility. Additionally, the dynamic doping effect of Cu atoms from the decomposition of AgCuTe within the matrix further optimize the high-temperature thermoelectric performance. Overall, these factors significantly enhance the ZT across the whole temperature range. The ZT value of ≈1.5 indicates high competitiveness compared to the latest reported n-type PbSe materials, suggesting that these findings hold promise for advancing the development of efficient thermoelectricsystems.

Wear and corrosion resistance of TiAlSi-Nix (x = 0, 5, 11, 17, 23 at%) multi-principal component alloy coating prepared by ∞ oscillating laser cladding

To improve the wear and corrosion resistance of key components and ensure the safe operation of offshore equipment, we applied an ∞ oscillating laser to prepare a TiAlSi-Ni composite coating. The effects of Ni addition on the composition, microstructure, corrosion resistance and mechanical properties of the coating were experimentally investigated. The results showed that the coating mainly presented an interdendritic - dendritic structure, and the S4 coating with 17 at% Ni had the best wear and corrosion resistance. In the reciprocating sliding friction and wear test at 10 N and 30 N, the wear rates were 0.83 and 1.66 × 10−7 mm2·N−1, respectively, which is 1/5 and 1/3 of TC4 under this load. The S4 also had the largest passivation interval and passivation film stability. The internal and external double-layer film structure ensures that it is not corroded by corrosive medium. The Ti3Al/TiNi semi-coherent interface and lattice distortion gave the Ti3Al-Ti2Ni and TiAl-TiNi eutectic interfaces a high bonding strength. Moreover, the “labyrinth effect” produced by the lamellar eutectic structure further improved the corrosion resistance. This work provides a new method for obtaining coatings with high adhesion and wear and corrosion resistance for offshore platforms.

A new insight into largely defocused HAADF-STEM imaging and visualization of strain field

A crystalline bilayer specimen with a semi-coherent interface can generate moiré fringes in the high-angle annular-dark field scanning transmission electron microscopy (HAADF-STEM) imaging. Moreover, when the probe is significantly defocused, this specimen can produce largely defocused probe (LDP)-STEM patterns. Although the electron channeling effect serves as the fundamental principles for HAADF-STEM imaging, its connection to the emergence of LDP-STEM patterns remains unclear. The missing link lies in identifying the location of the imaged region. To address this issue, we examined the strain field in three-dimensional space and its interaction with the convergent electron beam, taking the PbZrO3/SrTiO3 (PZO/STO) heterostructure as an example. We discovered a new intensity relationship for LDP-STEM patterns in the PZO/STO heterostructure, which can be well explained by our theory. We also found that, generated by imaging the strain zone, these patterns revealed information that might be obscured in traditional high resolution STEM images, showing a unique advantage in characterizing the strain field. Furthermore, we provided discussions on visualizing the strain field, including the misfit dislocation network and array. Our research offers a novel perspective on the LDP-STEM imaging and clarifies the approach to characterizing the strain field.

The Effects on Stability and Electronic Structure of Si-Segregated θ′/Al Interface Systems in Al-Cu Alloys

This study systematically investigates the energy and electronic properties of Si-segregated θ′(Al2Cu)/Al semi-coherent and coherent interface systems in Al-Cu alloys using ab initio calculations. By evaluating the bonding strength at the interface, it has been revealed that Si segregated at the A1 site (Al slab) of the semi-coherent interface systems exhibits the most negative segregation energy, resulting in a noticeable decrease in total energy and an increase in interface adhesion. The electronic structure analysis indicates the presence of Al-Cu and Al-Al bonds, with Si occupying the A1 site. The strong bond formation between Al-Cu and Al-Al is essential for improving interface bonding strength. The results of the calculating analyses are consistent with the results of the previous experiments, and Si can be used as a synergistic element to reduce the θ′/Al interface energy and further reduce the coarsening drive of the θ′ precipitated phase, which can provide new perspectives and computational ideas for the compositional design of heat-resistant Al-Cu alloys.

Strength-ductility synergy of a laser welded 7085Al matrix nanocomposite joint: Interaction between ZrB2, Al3(Er, Zr) nanoparticles and MgZn2 precipitates

The dissolution and coarsening of precipitates during welding thermal cycle weakened mechanical properties of 7xxx Al alloy joints. In this work, ZrB2 ceramic nanoparticles and core-shell structured Al3(Er, Zr) (L12) with high thermal stability were introduced to synergistically enhance the mechanical property of laser welded 7085Al nanocomposite joint, and the interaction between ZrB2, Al3(Er, Zr) nanoparticles and MgZn2 precipitates was analyzed. The results showed that grain boundaries were covered by fine precipitates with discrete distribution under the action of ZrB2 and Al3(Er, Zr). The interface coherency of ZrB2/Al and Al3(Er, Zr)/Al was improved by introducing highly coherent MgZn2 precipitates to form coherent multi-interfaces of ZrB2/MgZn2/Al and Al3(Er, Zr)/MgZn2/Al. The ultimate tensile strength and uniform elongation of ZrB2/7085Al-Er nanocomposite joint were 678.9 MPa and 18.5 %, with a 36.6 % and 55.5 % increase as compared to 7085Al counterpart. The reinforced grain boundary can prevent strain localization here and allow the activation of high density of dislocations within grains. The higher interface coherency could effectively promote the dislocation multiplication and dislocation annihilation, relieving stress concentration at semi-coherent interface caused by dislocation pile-up. Finally, the strength-ductility synergy was achieved in ZrB2/7085Al-Er nanocomposite joint by strengthening grain boundary and tailoring interface structure.

Rational design of a setaria-like NiTe2/MoS2 semi-coherent heterogeneous interface for enhancing diffusion kinetics in potassium-ion batteries

Constructing unique heterostructures is a highly effective approach for enhancing the K+ storage capability of transition metal selenides. Such structures generate internal electric fields that significantly reduce the charge transfer activation energy. However, achieving a flawless interfacial region that maintains the optimal energy level gradient and degree of lattice matching remains a considerable challenge. In this study, we synthesised Setaria-like NiTe2/MoS2@C heterogeneous interfaces at which three-dimensional MoS2 nanosheets are evenly embedded in NiTe2 nanorods to form stabilised heterojunctions. The NiTe2/MoS2 heterojunctions display distinctive electronic configurations and several active sites owing to their low lattice misfits (δ = 13 %), strong electric fields, and uniform carbon shells. A NiTe2/MoS2@C anode in a potassium-ion battery (KIB) exhibited an impressive reversible capacity of 125.8 mAh/g after 1000 cycles at a rate of 500 mA g−1 and a stable reversible capacity of 111.7 mAh/g even after 3000 cycles at 1000 mA g−1. Even the NiTe2/MoS2@C//perylene tetracarboxylic dianhydride full battery configuration maintained a significant reversible capacity of 92.4 mAh/g after 100 cycles at 200 mA g−1, highlighting its considerable potential for application in KIBs. Calculations further revealed that the well-designed NiTe2/MoS2 heterojunction significantly promotes K+ ion diffusion.

Nickel-Induced charge transfer in semicoherent Co-Ni/Co6Mo6C Heterostructures for reversible oxygen electrocatalysis

To achieve high-performance Zn-air batteries (ZABs), the development of bifunctional air electrodes capable of efficiently mediating both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is imperative. In this study, we present an N-doped carbon hollow nanorod encapsulating a semi-coherent Co-Ni/Co6Mo6C heterojunction, tailored for reversible oxygen catalysis. This nanohybrid demonstrated an ORR half-wave potential of 0.907 V alongside an OER overpotential of η10 = 352 mV. When incorporated into ZABs, this catalyst exhibited extraordinary performance metrics, including a high-power density of 343.7 mW/cm2, a specific capacity of 681 mAh/gZn, and enhanced durability. The distinctive electric field within the heterojunction facilitated electron transfer across the semi-coherent interface during reversible oxygen electrocatalysis, enhancing the adsorption and release of active intermediates. Thus, this heightened ORR-OER catalytic efficiency culminated in superior ZABs performance. Our findings afford a pivotal design paradigm for the advancement of productive bifunctional catalysts within the field of energy conversion technologies.

Multiple semi-coherent particles strengthened ultra-fine-grained Al composites for neutron shielding materials

Neutron shielding materials face imbalanced behaviors among shielding, strength, and ductility properties. Based on the requirement of the high property shielding particles, a superior semi-coherent τ(Al4MgGd) phase was designed and predicted by cluster expansion (CE) method using density functional theory calculations. To realize its shielding property, the Powder Metallurgy-based routines (i.e., powder fabrication, spark plasma sintering, and hot extrusion techniques) are used to fabricate 6TiB2/Al-6Mg-5Gd (wt.%) composite with dispersed refined τ phases and homogenized TiB2 distribution. The atomic structure of ternary phase τ is examined by aberration-corrected high-angle annual dark-field (HAADF) scanning transmission electron microscope (STEM) and energy dispersive X-ray spectroscopy (EDXS) STEM experiments, which is well complied with the calculated compound (Al4MgGd). In detail, the τ(Al4MgGd) phase has a semi-coherent interface both with α-Al and TiB2, which is consistent with the prediction of interface relationships. With the optimized interfaces, the TiB2 and τ phases can effectively promote recrystallization and suppress grain growth, leading to the formation of ultra-fine grain structure. Then, the composite exhibits advanced shielding properties (Macroscopic transmission cross section ∼24.1 /cm, higher than 30 %B4C/Al) and optimized synergic mechanical properties (Ultimate tensile strength ∼506 MPa, elongation ∼12.9 %), which are far higher than available Al-based neutron shielding materials. Finally, the underlying strength-ductility mechanisms are discussed. Critically, the design and optimization of shielding particle interfaces are reliable strategies for developing novel structural-functional integrated materials.

Influence of CrAlN layers on the microstructure, thermal stability, oxidation and corrosion resistance of AlN/CrAlN multilayers

Recently, the development of AlN-based multilayers has raised interest due to the probability of improved performance from both Al-addition and multilayer architecture. Here we prepared AlN/Cr1-xAlxN (x = 0.44 and 0.64) multilayers, with monolithic AlN and Cr1-xAlxN coatings as reference. The dependence of microstructure, mechanical properties, thermal stability, oxidation and corrosion resistance on Al content of CrAlN layers were investigated in detail. The AlN/Cr0.56Al0.44N (low-Al ML) shows a superlattice feature with single-phase face-centered cubic (fcc) structure and its hardness is 29.7 ± 1.0 GPa, which is ∼4.8 GPa higher than the theoretical value from rule of mixture. While the increase of Al content in CrAlN layer leads to a mixed cubic and wurtzite structure of AlN/Cr0.36Al0.64N (high-Al ML) with semi-coherent interface. Accordingly, the high-Al ML only has a hardness of 16.9 ± 0.4 GPa. During annealing, AlN/Cr1-xAlxN multilayers reveal hindered decomposition of CrN bonds, compared with the corresponding Cr1-xAlxN monoliths. The low-Al ML possesses the best thermal stability, reflected by its high hardness maintained up to 1000 °C, which is 100 °C higher than Cr1-xAlxN monoliths. Additionally, AlN/Cr1-xAlxN multilayers show improved oxidation resistance, with high-Al content in CrAlN layers favorable for such resistance. After oxidation at 1100 °C for 15 h, the low-Al ML and high-Al ML generate oxide scales with thicknesses of ∼1.6 and ∼1.4 μm, respectively, compared to the fully oxidized Cr0.56Al0.44N and ∼1.8-μm-thick oxide scale of Cr0.36Al0.64N. In electrochemical experiments, the corrosion current density (Icorr) of multilayer coatings decreases, compared to their corresponding monolithic coatings.

Investigation of coherent interface on relaxation behavior and reliability of Mg-doped BaTiO3 dielectric ceramics: Experiments and first-principle calculations

The addition of Mg generally enhances the high-temperature stability and reliability of BaTiO3-based multilayer ceramic capacitors (MLCCs). Herein, a series of Mg-doped BaTiO3-based ceramics and ultra-thin MLCCs were successfully fabricated, and the coherent and semi-coherent interface has been observed in samples. Based on the density functional theory (DFT) calculations, the improvement in temperature stability is due to changes in the coherent interface and electronic structure that promote the formation of polar nano-regions (PNRs) and induce relaxation behavior. Based on the atomic displacement, it is found that the excess substitution released the coherent stresses in the form of defects and formed semi-coherent interfaces. The reliability degradation of MLCCs is mainly due to the evolution of the semi-coherent interfaces. This work points out an avenue to obtain high-temperature stability and high reliability in BaTiO3-based MLCCs.

Improving mechanical properties of W-Ni3Al alloy through Zr element addition: Solid-solution and oxide particle strengthening

In this study, fine Ni3Al flakes facilitated the W-Ni3Al alloy liquid phase sintering, while the added 0.9 wt% Zr element enhanced its mechanical properties, finally obtaining the 1200 °C sintered W-Ni3Al-Zr alloy (WNZ-1200 alloy) with excellent comprehensive properties. Specifically, the relative density, tungsten grain size, bending strength, and macro hardness of WNZ-1200 alloy were 98.26 ± 0.31 %, 3.06 ± 0.65 µm, 1472.56 ± 61.90 MPa, and 76.10 ± 0.82 HRA, respectively. By analyzing the alloy’s phase and microstructure, its excellent mechanical properties were originated from the formed Ni3(Al, W, Zr) solid solution, unique nano-Al2O3 ‘rivet’, the semi-coherent interface of W/t-ZrO2, oxide dispersion strengthening, and the t-ZrO2 phase transformation strengthening.