Phase Constitution Research Articles

Properties of Al0.5CoCrFeNi2Ti High-Entropy Alloy System: From Gas-Atomized Powders to Atmospheric Plasma-Sprayed Coatings

AbstractThe performance of the Al0.5CoCrFeNi2Ti HEA atmospheric plasma-sprayed coating was extended from characterizing the properties of its powder prepared via the gas atomization method. It was observed that the gas-atomized HEA powders possessed a solid solution BCC phase, while a major phase transformation to a FCC-L21 intermetallic phase occurred during the annealing process. The formation of the intermetallic phase resulted in an increase in average hardness from 6.28 to 7.64 GPa after annealing at 900 °C for 1 h. Afterward, HEA powders were applied in the atmospheric plasma spray technology. The phase constitution of Al0.5CoCrFeNi2Ti HEA coatings was investigated by varying powder size and applied current. It was observed that the smaller powder sizes prone to oxidation, whereas higher applied current facilitated the phase transformation from BCC to FCC phase. The nanoindentation test indicated distinct average microhardness values for the interlamellar oxide region, BCC unmelted particle and FCC phase lamellar region, which was measured at 12.35, 8.68 and 5.97 GPa, respectively. As a result, the adjustability of coating hardness was achieved by manipulating the relative phase ratio.

Preparation and characterization of core-shell structured CaCO3-SiO2 and hollow silica nanoparticles and evaluation of their effects on cement mortar properties

CaCO3-SiO2 particles having a core-shell nanostructure were produced by a modified Stöber process using CTAB as a surfactant. Then, a porous structure composed of a silica shell was formed after the removal of the CaCO3 cores as templates from the nanocomposite. To evaluate phase constitutions and microstructures of prepared nanoparticles, XRD, TEM, and FESEM–EDX techniques were utilized. The main aim of this work was to examine the usability of prepared CaCO3-SiO2 and SiO2 hollow shell nanoparticles instead of OPC in structural applications. In this way, the mixtures of cement mortar were made by partial replacement of 1% of cement mass with prepared nanoparticles. The amounts of calcium hydroxide (CH), bound water, and calcium carbonate for the prepared mortars have been calculated after 7 and 28 days of hydration through thermal analysis of TG/DTG. The results indicated that the CH content decreased by adding prepared nanoparticles as a cement replacement. As CaCO3-SiO2 and hollow SiO2 nanoparticles were used, the compressive strengths of mortars were enhanced by 34 and 59%, respectively, after 28 days, which were higher than the increasing influences on flexural strengths (29 and 55%). The increasing intensity of the XRD peaks related to the C-S-H phases and the decline of the orientation index of CH in a mortar containing silica shell suggest that hydration was further completed, leading to a strength improvement. The SEM micrographs indicated that the addition of prepared nanostructures improved the interface properties inside mortar and caused the microstructure to be denser.

In-situ synchrotron high energy X-ray diffraction study on the compressive creep behavior of an extruded Ti-45Al-8Nb-0.2C alloy

Wrought high Nb containing (high Nb-TiAl) alloys are potential materials for low pressure turbine blades in aero-engines. The performance and microstructure evolution under high temperature creep condition is of importance to the service stability of these materials. In this study, the internal strain and FWHM evolution of an extruded TNB-based high Nb-TiAl alloy during compressive creep are characterized by in-situ high energy X-ray diffraction (HEXRD) technique for the first time. The compressive creep test was conducted under a constant load of 300 MPa at 900 °C for 10 h in vacuum. The final creep strain is approximately 1.72 %. The microstructure and phase constitution after creep shows little difference from that before creep. Lattice strain analysis shows that γ phase is plastically deformed while the α2 phase deforms elastically due to the low creep strain. The lattice strain of α2 grains is dependent upon the deformation of surrounding γ grains. Creep induces dynamic recovery, exerting a softening effect. A high number of dislocations are visible in the γ lamellae while almost no dislocations exist within the α2 lamellae. α2 lamellae are partially decomposed and refined via the α2→γ transformation.

Tuning ferroelectric domains and polarization properties of flexible BiFeO3 thin films by phase transition engineering

In the present investigation, thin films of flexible (Bi1-xSmx)(Fe0.95Mn0.05)O3 (denoted as BSFM0, BSFM4, BSFM8, and BSFM12 for x=0 %, 4 %, 8 %, and 12 %, respectively) were synthesized on metallic Ni-Cr substrates via the sol-gel technique. A comprehensive examination was conducted to elucidate the influence of varying concentrations of Sm3+ substitution on the phase constitution, oxygen vacancy concentration, and leakage behavior of the (Bi1-xSmx)(Fe0.95Mn0.05)O3 films. Utilizing X-ray diffraction (XRD) and Raman spectrometry, it was ascertained that all films exhibited a composite structure comprising orthorhombic (Pnma) and rhombohedral (R3c) phases. An augmentation in Sm3+ doping led to a non-monotonic variation in the R3c phase content, initially increasing and subsequently decreasing, while the nonpolar Pnma phase demonstrated a progressive enhancement. The distorted R3c phase was found to promote the flipping of the domain architecture, thereby augmenting the polarization attributes. Notably, at a Sm doping level of 4 %, the maximum polarization (Pmax) attained was 95 μC/cm2, with a remnant polarization (Pr) of 78 μC/cm2. The incorporation of a judicious amount of Sm was observed to curtail film leakage and decelerate the aging phenomenon. The compositional stability of this doping level was evaluated across a frequency spectrum of 0.1–12 kHz and a temperature gradient of 25–200 °C, revealing no propensity for degradation under conditions of polarization, a holding duration of 104 s, or fatigue scenarios involving a curvature of 5 mm and 108 switching cycles subjected to 103 instances of bending. These findings provide innovative insights for the development of next-generation lead-free transducer apparatus and flexible information storage mediums.

Improved mechanical properties of W-Zr-Ti-Nb alloys via adding Ti and Nb

Formation of the W2Zr intermetallic is the key reason for the low relative density and brittleness of W-Zr alloys. In this study, 65 W-Zr-Ti-Nb alloys with different Ti and Nb content were prepared by powder metallurgy. With the increase of Ti and Nb content, the proportion of the W2Zr in the alloy decreases, causing the densification of 65 W-Zr-Ti-Nb alloys. The thermodynamic calculation shows that the addition of both Ti and Nb results in a narrowing stabilized temperature range of W2Zr and an expanding stabilized temperature range of BCC-WTixNby, respectively, ultimately causing the disappearance of the W2Zr and formation of the WTixNby during non-equilibrium cooling. Both high ductility and strength can be achieved in the W-Zr-Ti-Nb alloys by assistance of the disappearance of the brittle W2Zr phase and the formation of the ductility WTixNby. The first principle calculation indicates that the co-doping Ti and Nb results in a larger expansion on the spacing of the {110} close-packed plane and a smaller expansion or even shrinkage on the atomic spacing along the close-packed direction of the WTixNby. Further, integrated crystal orbital Hamilton population (ICOHP) results proved that the bonding strength of W-Ti and W-Nb was weaker than that of W-W in WTixNby. Both increased spacing of {110} plane and decreased interatomic bonding strength aid in reducing Peierls-Nabarro stress, promoting plastic deformation. This study provides a new method for improving mechanical properties by tailoring the phase constitution in W-Zr alloys through co-doping Ti and Nb.

The effects of Nb on the microstructure and performance of laser-cladded Fe50-xMn30Co10Cr10Nbx high entropy alloy coatings

A laser cladding technique was employed to produce a Fe50-XMn30Co10Cr10NbX (X = 2.5, 5, 7.5, 10at%) high entropy alloy coating. This study delved into the influence of Nb concentration on the coating’s phase constitution, microstructural features, hardness, and wear resistance. The high entropy alloy coating exhibited a multifaceted structural composition, encompassing FCC (Face-Centered Cubic), HCP (Hexagonal Close-Packed), and BCC (Body-Centered Cubic) structures, along with the presence of Laves phase. Notably, the incorporation of Nb led to an augmentation in the Laves phase and modifications within the microstructure. The hardness of the cladding layer is higher than that of the substrate. With the increase of Nb content, the hardness of the cladding layer increases first and then decreases; the average hardness of the Fe42.5Mn30Co10Cr10Nb7.5 cladding layer is the highest, the maximum hardness is 429.8Hv, and the average hardness is 382.3Hv. The friction coefficient and weight loss of the cladding layer decreases first and then increases with the increase of Nb content. The friction coefficient and weight loss of the Fe42.5Mn30Co10Cr10Nb7.5 cladding layer are the smallest, which are 0.0132 g and 0.5974, showing the best wear resistance. The wear types of high entropy alloy cladding layer are both adhesive wear and abrasive wear. The addition of Nb into high entropy alloy will form the Laves phase, which can improve the mechanical properties of high entropy alloy.

Enhancing strength performance of laser welded 7075 aluminum alloy joints with TiC nanoparticle-mixed filler powder

Precipitation-strengthened 7075 aluminum alloy (AA 7075) is a crucial structural material widely utilized in the aerospace industry. Nevertheless, the achievement of highly strengthened joints of this alloy remains a challenge because of its susceptibility to composition dilution and defect formation during welding. In this study, the method of powder-filled laser welding was employed to weld AA 7075-T6 plates, utilizing both AA 7075 powder and a mixed powder of AA 7075 and 5 wt % TiC nanoparticles as the filler. To investigate the impact of the filler on the mechanical properties of the welded joints, their microstructure, phase constitution and tensile strength were measured and analyzed. Moreover, the transient temperature and the forming process of the joints during laser welding were captured. The results indicate that the joints are heat-treatable when the filler contains the AA 7075 powder. The ultimate tensile strength (UTS) of the joints can reach 500 MPa as a result of the η′ phase precipitated during heat treatment. The incorporation of TiC nanoparticles into the AA 7075 powder led to a refinement of grains, a reduction in porosity within the joints and an increase in the UTS by up to 540 MPa, which is 91.5 % of the base metal. Further theoretical estimation suggests that Orowan strengthening as well as grain size strengthening due to the Hall-Petch effect are the main strengthening mechanisms for the improved tensile performance. The powder-filled laser welding method also provides a flexible approach for designing compositions of filler material.

Modulating Phase Constitution and Copper Microsegregation for FeCoNiCuAl High-Entropy Alloy by Optimized Ultrasonic Solidification

Modulating Phase Constitution and Copper Microsegregation for FeCoNiCuAl High-Entropy Alloy by Optimized Ultrasonic Solidification

Effect of the Laser Cladding Parameters on Microstructure and Elevated Temperature Wear of FeCrNiTiZr Coatings.

In order to prepare coating with good friction and wear resistance at elevated temperature on the surface of hot-working tool steel, by using a CO2 laser, FeCrNiTiZr high-entropy alloy coating with different laser scanning speeds (360, 480 and 600 mm/min, respectively) was successfully fabricated by using laser cladding technology on the surface of H13 steel in this paper. Phase constitutions, microhardness, microstructure, and wear characteristics of FeCrNiTiZr coatings under different laser scanning speeds were analyzed. It was determined that 480 mm/min was the optimal laser scanning speed. The results showed that the coating at the scanning speed of 480 mm/min consists of a BCC phase with significant lattice distortion and high dislocation density; the crystal structure is cellular crystal and dendrite crystal. The coating demonstrates the highest microhardness (842 HV0.2), which is 4.2 times that of the substrate (200 HV0.2). Its average friction coefficients at room temperature and 823 K are approximately one-seventh and one-third of the substrate's, respectively, and its wear volume is reduced by about 98% and 81% under these conditions. Compared to the substrate, the coating underwent slight abrasive wear, adhesive wear, and oxidative wear at both room temperature and 823 K. In contrast, the substrate underwent severe abrasive wear, adhesive wear, oxidative wear, and even fatigue wear.

Effect of chemical inhomogeneity on the structure and properties of the two-layer TiAl-based coating obtained by non-vacuum electron beam cladding: Experimental investigations and density functional theory simulations

Non-vacuum electron beam cladding is a highly effective technology for producing protective coatings on metal workpieces. In this study, the 3.8 mm thick TiAl-based coating with Cr and Nb additions was obtained on the Ti alloy substrate in two passes of the electron beam. To evaluate inhomogeneity of the two-layer coating, energy-dispersive synchrotron X-ray diffraction (EDSXRD) in combination with energy-dispersive X-ray spectroscopy (EDX) was applied. It was found that in the direction from the top of the coating to the substrate, the dilution of the cladding layers with Ti increased. It influenced the phase constitution of the coating and led to a variation in the chemical composition of different phases (α2-Ti3Al, β-phase, and TiN). The properties of the first (lower) and the second (upper) cladding layers were evaluated separately. The upper layer exhibited greater oxidation resistance than the lower one due to the presence of the γ-phase, which has superior high-temperature stability compared to the α2-Ti3Al phase, predominant in the coating. The influence of varying chemical composition on the oxidation resistance was also estimated using density functional theory (DFT) simulations. It was found that decrease in Al content in the α2 phase leads to an increase in oxygen absorption energy. This could potentially result in a decrease in oxidation resistance. Wear resistance of the first and the second cladding layers was at the same level mainly due to the low contribution of minor phases. Additionally, DFT simulations show that the variations in chemical composition of the major phase (Ti3Al) are not likely to impact the coating wear resistance.

Phase analysis of near equiatomic bulk FeRh alloys: X-ray versus neutron diffraction and magnetization measurements

The information obtained by X-ray diffraction (XRD) by impinging the X-ray beam onto the flat surface of bulk Fe–Rh alloys is contrasted with that provided by the thermomagnetic analysis curves measured under a magnetic field of 5 mT and 2 T, and the neutron diffraction (ND) patterns. The experiments were performed on slices cut from bulk Fe50Rh50 and Fe49Rh51 alloys prepared by induction melting followed by 48 h of thermal annealing at 1273 K. Whereas ND patterns and magnetization curves, directly and indirectly point out that the samples are single-phase with a CsCl-type crystal structure undergoing a magnetoelastic transition that changes the magnetic structure from antiferromagnetic to ferromagnetic on heating, multiple phases are identified in the XRD patterns, which modify upon polishing or etching the surface with a mixture of hydrochloric (HCl) and nitric acid (HNO3) at a volume ratio of 90:10 from 30 to 210 min. The limitation of XRD for accurately characterizing the phase constitution within the bulk of Fe–Rh alloys is underlined.

Enhanced piezoelectric properties of KNN-based ceramics by synergistic modulation of phase constitution, grain size and domain configurations

Despite significant advancements in KNN-based piezoelectric ceramics, controlling their grain size remains a challenge, impacting reproducibility of piezoelectric properties. Here, we address this issue by initially investigating the defect chemistry of a ternary system 0.96 K0.48Na0.52Nb0.96Sb0.04O3-0.04Bi0.5Na0.5ZrO3-ABO3 (KNNS-BNZ-ABO3). The ABO3 dopant not only influences the phase constitution, but also induces different charge compensation mechanisms, affecting the grain size and domain configurations of ceramics. Furthermore, the relationship between the grain size and the piezoelectric properties is investigated. The superior piezoelectric charge coefficient (d33) of 435 pC/N, ultra-high planar mode electromechanical coupling factor (kp) of 0.62 and preferable temperature stability are obtained in KNN-based ceramics with large grain size (∼50 μm) and hierarchical domain structures. Finally, we elucidated the intrinsic and extrinsic contribution of the grain size on piezoelectric properties of KNN-based piezoceramics based on Rayleigh analysis. Our work provides an effective paradigm for the development of lead-free piezoelectric ceramics for industrial applications.

Developing advanced CrSi coatings for combatting surface degradation of N-type (Zr,Ti)Ni(Sn,Sb) and P-type (Zr,Ti)Co(Sn,Sb) half Heusler thermoelectric materials

In this study, advanced oxidation-protective CrSi coatings were developed and deposited on N-type (Zr,Ti)Ni(Sn,Sb) and P-type (Zr,Ti)Co(Sn,Sb) thermoelectric (TE) materials using an environmentally friendly closed field unbalanced magnetron sputtering PVD system. The oxidation behaviour of the CrSi-coated and uncoated samples was evaluated through static oxidation tests at 500 °C and 600 °C for 10h and 50 h, respectively. In addition, the samples were exposed to cyclic oxidation tests between 25 °C and 500 °C for 10, 30 and 50 cycles, with each cycle consisting of 1h of oxidation at 500 °C, to examine the coating ability to withstand thermal shock, which is involved in the service of TE devices. The surface morphology, cross-section layer structure, elemental distribution and phase constitution were analysed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD). The mass gain after the oxidation tests was measured and calculated for each sample to study the oxidation kinetics. The uncoated samples exhibited a considerable amount of oxidation, leading to change in the surface morphologies, and the formation of alternated layers including oxide products (Zr(Ti)O2, SnO2) and Ni3Sn4 compound for the N-type and (Zr(Ti)O2, SnO2, Sb2O4) and CoSb compound for the P-type material, after static and cyclic oxidation tests. The experimental work in this study has, for the first time, demonstrated that the CrSi coatings developed with very high thermal stability and oxidation resistance can effectively protect both the N-type and P-type materials from oxidation and sublimation even during cyclic oxidation tests. The strong affinity of Cr and Si to oxygen can trap oxygen, retard its inward diffusion and thus protect the TE material substrate from oxidation. This finding could pave the way towards the further development of long-life high-performance TE generators and devices, thus contributing to the net zero target.

Effects of rare earth on nitriding microstructure and properties of a La-Ce micro-alloyed Q235RE steel

Accelerating nitriding is an interesting topic in chemical heat treatment of ferrous parts. In order to have a deeper understanding of the catalysis principles of rare earth in nitriding, a Q235 carbon steel and a Q235RE steel micro-alloyed with rare earth elements La and Ce were nitrided respectively by plasma nitriding and gas nitriding. The microstructure, phase constitution, and composition of the nitrided specimens were analyzed. The hardness profile of nitriding layer and the brittleness of surface compound layer were measured. The results demonstrate that the Q235RE specimens obtained a higher hardness and deeper effective hardening layer than the Q235 specimens without rare earth microalloying. The rare earth catalysis effects were presented as the acceleration of nitrogen diffusion and the inhibition of nitride precipitation in the diffusion layer of the Q235RE specimens. In addition, the surface compound layer of the Q235RE specimens showed higher toughness and better adhesion to the matrix than that of the Q235 specimens, which is considered to be strongly related to the rare earth elements diffused into the compound and the enhanced residual compressive stress in the layer.

Oxidization on phase transformations in Ti-Nb high temperature shape memory alloys

Properties of metastable β-Ti alloys can be optimized by tuning the rich phase transformations. Oxygen (O) introduction, inevitable during melting and processing, affects greatly on phase transformations and the associated properties in β-Ti. We investigated the effects of oxidation on phase transformations in Ti-Nb alloys. Based on microscopic characterizations, the as-quenched microstructure of oxidized Ti-20 Nb is revealed to contain 3 distinct layers with respect to the phase constitutions and subsequent transformations, i.e. oxide, oxygen influenced (OI), and center (C) layers. On subsequent heating, β→ωiso occurs in OI layer, and in C layer undergo successive two step α”→β and β→ωiso transformations. In C layer of low O-content, both the starting temperatures of α”→β (AsC) and β→ωiso (ωsC) transitions increase slightly with O-content. In OI layer of high O-content, since the β→α” transition is suppressed upon quenched to 273 K, the retained β starts to precipitate ωiso far below ωsC upon subsequent heating. In summary, with the increase of O-content, the As and ωs slightly increase at low O-content and then undergo a drastic decrease. The underlying mechanisms are further discussed. Our work may shed lights on the high temperature thermomechanical processing and designing high performance metastable β-Ti alloys.

Simultaneously enhancing mechanical and tribological performance in undercooled Co-18.5 at. % B alloys

The wear behavior and its mechanism greatly depend on the microstructure of alloys. Herein, the Co-18.5 at. % B eutectic alloys with three different morphologies and phase constitutions were obtained by undercooling solidification under different magnetic field intensity (0T, 10T, 20T), and the relative mechanical properties and tribological performance were investigated systematically. Results show that the grain size of Co–B alloy decreases first and then increases with the increase of magnetic field strength, the average grain size of samples under 0 T and 20 T was about 3–5 μm, while the grain size of sample with 10 T refined to 20–40 nm. The sample treated under 10 T exhibits the lowest wear rate (1.53 × 10−5 mm3N−1m−1) and highest micro-hardness (868.27 HV). The fine grain strengthening effect is the main reason for the increase in strength and hardness of Co–B alloy. The fine crystalline nano-heterostructures (20–40 nm) and the precipitation enhancement of secondary precipitated Co nanoparticles also has a beneficial effect on mechanical properties. The oxide friction layer consisting mainly of layered H3BO3 lubricant, detected on the worn surface of Co–B alloy (10T) has anti-wear properties. By contrast, Co–B alloys with coarse Co3B grains (0T) and inhomogeneous FCC-Co/Co2B lamellar structure (20T) present higher wear rates and lower hardness. This work can provide guidance for the initial control of mechanical properties from the design of the microstructure.

Microstructures and properties of Cu/50 vol% MoS2 composites prepared with Cu-coated MoS2 powders and sintered at different temperatures

Constitution and distribution of phases and interphase reactions are crucial for properties of composites. So far, the problem of MoS2 agglomeration remains unsolved in Cu/MoS2 composites, and interfacial structures and reaction products between MoS2 and Cu have not been fully considered. Herein, Cu-coated MoS2 powders prepared via electroless plating were sintered at different temperatures into Cu/MoS2 composites. Cu does not react with MoS2 in the composites sintered at 600 ℃ and 650 ℃, leading to their desirable tribological properties under dry sliding. Reactions between Cu and MoS2 occur in the composites sintered at 700 ℃ and 800 ℃, and the resultant products include Cu2S, Cu1.8Mo6S8 and Cu1.83Mo3S4 phases, resulting in a better wear resistance under oil lubrication and mechanical properties.

Phase stability and transition of CrTaVW high-entropy alloy

Refractory high-entropy alloys (RHEAs) are susceptible to phase transition at elevated temperatures, inducing deviation in the phase constitution from the intended design hence affecting the performance significantly. Accurate prediction of phase constitution and modulation of phase stability over a broad temperature range is crucial to develop RHEAs with superior properties. In this study, thermodynamic and first-principles calculations were integrated to investigate the temperature-dependent phase constitution in the CrTaVW alloy system. The effect of V and W atoms occupation sites on the stability of TaCr2 Laves phase was evaluated. Both V or W atoms tend to occupy Cr sites in TaCr2, and V exhibits stronger alloying ability than W due to the reduced electronic density at the Fermi level. Moreover, with increasing the doping content, the V and W exhibit opposite influencing trends on the formation and structural stability of TaCr2 Laves phase. The Gibbs free energies of the Laves phase and solid solutions with variable compositions were obtained, enabling predictions for the critical temperatures of the phase transitions. The predicted behaviors of phase transitions were validated by experiments. This study provides guidance for modulating phase constitution and achieving desirable phase stability in RHEAs.

Harnessing Cu incorporation for achieving stable superior microwave dielectric properties in low permittivity MgSiO3-based ceramics through effective phase transition suppression

MgSiO3 ceramics with a low dielectric constant are highly promising for application in 5G communication due to their excellent performance and cost-effectiveness. However, the application remains constrained by phase transitions. This study aims to unlock their full potential by introducing Cu ions to mitigate phase transitions, thereby achieving stable and superior performance. Mg1-xCuxSiO3 (0 ≤ x ≤ 0.25) ceramics were synthesized by solid-state method, and the effects of Cu introduction on the crystal structure, phase constitution, microstructure and microwave dielectric properties were systematically investigated. Through XRD patterns and Rietveld refinement, it was found that when x = 0, both protoenstatite (PEN) and low-temperature clinoenstatite (CEN) phases coexist due to a phase transition from PEN to CEN. As x increases, the PEN phase dominance rises while the CEN phase diminishes, indicating that the addition of Cu ions inhibits the occurrence of phase transition. At x ≥ 0.2, only the orthoenstatite (OEN) phase was observed. SEM and EDS analyses revealed the beneficial impact of Cu introduction on sintering, yet excessive amounts can lead to abnormal grain growth, local segregation, and uneven distribution of Cu elements, thereby deteriorating microwave dielectric properties. The optimal microwave dielectric performance was achieved at x = 0.05: εr = 6.2, Qf = 93,600 GHz, τf = −33.7 ppm/°C. A one-year long-term comparative study revealed the stabilizing effect of Cu incorporation for obtaining stable excellent performance. These findings underscore the potential of introducing an appropriate amount of Cu to achieve stable and superior microwave dielectric properties in MgSiO3 ceramics, paving the way for practical applications in 5G communication.

Acoustic cavitation-induced microstructure evolution in ultrasonically brazed Al/Cu joints using Zn-Al alloy fillers

Tailoring the phase constitutions of the interfacial reaction layers under the assistance of ultrasonic vibration is a convenient method to fabricate high-strength Al/Cu brazing joints. In this study, 1060-Al and T2-Cu dissimilar metals were ultrasonically brazed with Zn-3Al (wt. %) filler metals. Effects of ultrasonic brazing time on the microstructure and mechanical properties of joints were investigated. Results showed that the CuZn5 intermetallic compound (IMC) layer and Cu-based diffusion layer were created on the Cu substrate surface in the joint ultrasonically brazed at 400 ℃ for 2 s. However, the CuZn5 IMC layer was gradually transformed into a thin Al4.2Cu3.2Zn0.7 IMC layer by increasing the ultrasonic vibration time to 15 s. A well-matched coherent interface was formed between the Al4.2Cu3.2Zn0.7 ternary phase and the Cu-based diffusion layer. The phase transition of the Cu-side interfacial layer correlated closely with the acoustic cavitations induced super-saturation regions near the Cu substrate surface. The measured tensile strength of the Al/Zn-3Al/Cu joint ultrasonically brazed for 15 s was 89.3 MPa, which was approximately 2.5 times higher than that brazed for 2 s, and the tensile failure mainly occurred at the interface between the Al4.2Cu3.2Zn0.7 layer and the Cu-based diffusion layer.