Eutectic Phase Research Articles

Nano-microcrystals revealed on Tang dynasty gilded bronze using advanced TEM-SEM and synchrotron methods.

Over the years, numerous gold and silver artifacts have been excavated from the tombs of the Tang dynasty, which give evidence of the sophisticated metalworking techniques at that time. Few of the artifacts were thoroughly studied and their manufacturing processes were barely known. The present investigation concerns a metal headgear from a newly excavated tomb of a female in Xi'an of the Tang dynasty (618-907 A.D.), using advanced techniques in a complementary way, especially performing a detailed analysis of the corrosion products and alloying processes. The combined state-of-the-art methods and instrumentation used for the corrosion study included spectroscopy, diffraction, electron microscopy, synchrotron and their versions for specific measurements and sample preparation. The investigated headgear metal consists of a copper-based core, which is gilded by a thin gold layer, consisting of an Au-Hg alloy with a thin layer of about 400 nm. The technique used for shaping and hammered embellishments led to the creation of nanosized grains on the side that would eventually be the interior of the headgear. It was gilded using the mercury-amalgamation process, and the liquid diffusion caused the development of intermetallic compounds. This is the first recorded instance of these nano-scale and eutectic phases being observed on objects from an archaeological context. The crystallographic analysis offered valuable insights into the formation of needle-like malachite crystals growing on a layer of cuprite found on the surface of the corroded piece. The results highlight that the artisans utilized advanced methods in the creation of funerary items during the Tang dynasty.

Energizing eutectic salt hydrate phase change material using 2D carbon based graphene nanoparticle

Energy being the strongly depended source for development and industrialization, their storage in any form tends to bridge the gap between demand and supply. Renewable energy technology systems now include energy storage as a crucial component. Thermal energy storage is a technique that stores thermal energy by heating or cooling a storage medium. This allows the energy to be used for heating and cooling purposes later on. The present study develops ternary inorganic salt hydrate eutectic phase change material (EPCM) that is intended for cooling buildings. Melting temperature, melting enthalpy and eutectic composition proportion of inorganic salt hydrate of sodium carbonate decahydrate (SCD), sodium phosphate dibasic dodecahydrate (SPDD), and sodium sulphate decahydrate (SSD) are determined using the eutectic melting point theory. Ternary EPCM is synthesised experimentally in accordance with the percentage of salt hydrates. Graphene nanoplatelets are distributed at different weight concentrations of 0.3%, 0.6%, and 0.9% in order to further improve the thermal performance; at higher concentration above 0.9% the graphene nanoplatelets tends to agglomerate. In order to assess the chemical stability and thermal properties of prepared nanoparticle dispersed PCMs, are experimentally assessed. Findings confirm the ternary EPCM's chemical stability and raise its latent heat with graphene nanoplatelets.

The protocatechuic acid-based deep eutectic solvent-mediated green synthesis of 1,2,4,5-tetrasubstituted imidazoles.

A novel protocatechuic acid-based deep eutectic solvent (ETPPBr/PCA-DES) was prepared by mixing ethyltriphenylphosphonium bromide (ETPPBr) and protocatechuic acid (PCA = 3,4-dihydroxybenzoic acid), and its structure was fully investigated by using the FT-IR, TGA/DTA, densitometer, eutectic point and 1H NMR techniques. Different molar ratios of ETPPBr to PCA were examined and the eutectic point phase diagram showed that the best ratio for the synthesis of the new DES is the one-to-one ratio of the two starting materials (ETPPBr and PCA). Then, the novel DES was used as a new and capable catalyst for the green synthesis of diverse 1,2,4,5-tetrasubstituted imidazoles a1-a12 from the four-component condensation reaction of phenanthrene-9,10-dione, aromatic amine, aromatic aldehyde, and ammonium acetate with high yields and very short reaction times. High yields and very short reaction times are two advantages of our proposed method compared with the previous reported methods.

Effects of Y substituting Gd on the microstructure evolution, mechanical properties and dissolution behaviors in the Mg-Gd-Ni alloys used as fracturing plugging tools

In this work, the effects of substituting 3 wt% Gd with 3 wt% Y on the microstructure, mechanical properties, and corrosion behaviors in the Mg-Gd-Ni alloys were investigated. By substituting Gd with Y, the area fraction of bulk-shaped long-period stacking ordered phases (LPSO) increases, while one of eutectic Mg2Ni phase decreases slightly. Moreover, it also promotes the precipitations of lamellar LPSO phase and nanoscale stacking faults (SFs). The tensile tests showed that the addition of Y increased the yield strength by about 40 MPa, mainly due to the strengthening of the kink deformation of the bulk shaped LPSO phase, the hindering effect of the lamellar LPSO and SF on dislocation movement, and the strengthening caused by grain refinement. As a result, the Mg-5Gd-3Y–5Ni (MGYN) alloy exhibits excellent mechanical properties with tensile yield strength (TYS) of 288 MPa, ultimate tensile strength (UTS) of 364 MPa, and elongation (EL) of 8.3 %. Moreover, although the fraction of Mg2Ni phase with high electrochemical potential is decreased, the reduction in dissolution rate is not significant because the discontinuous distribution of lamellar LPSO in the grains intensifies the galvanic corrosion by increasing the proportion of cathode phase. As a result, the coexistence of Mg2Ni and LPSO phases can observably improve the dissolution rate. Finally, the highest dissolution rate (234.56 mg cm−2 h−1 in 3 wt% KCl solution at 93 °C) reported so far for the dissoluble magnesium alloys can be attained for MGYN alloy in this study. This work provides an economical material selection with high dissolution rate and sufficient strength for the fabrication of the fracturing plugging tools.

Experimental investigation on nucleating agent for low temperature binary eutectic salt hydrate phase change material

The melting enthalpy and melting temperature have a significant impact on the latent heat that results from phase change materials (PCMs) used for thermal energy storage. Among the PCMs that are currently on the market, inorganic salt hydrates have greater thermal conductivity and latent heat than organic PCMs. However, the problem of salt hydrates' degree of supercooling limits their use in energy storage devices. Using sodium carbonate decahydrate (SCD) and sodium phosphate dibasic dodecahydrate (SPDD), a low temperature inorganic-inorganic eutectic salt hydrate PCM with a higher melting enthalpy and intended phase transition temperature is developed in this research study. The eutectic SCD/SPDD salt hydrate PCM eutectic point and the eutectic composition of salt hydrate PCMs to operate at low temperature range is numerically determined using Schrader equation. By numerical methods we obtain the 68 wt% of SCD with 32 wt% of SPDD to exhibit eutectic SCD/SPDD composite with eutectic melting temperature of 26.2 °C and melting enthalpy of 210.6 J/g. The synthesised eutectic PCM are characterised to explore their chemical stability, latent heat, melting point and their shortcoming due to degree of supercooling. A good way to get around the problem of the supercooling degree is to disperse the nucleating agents. In order to assess the type and degree of supercooling, the produced eutectic PCM composition is experimentally evaluated at 1–10% utilising borax, alumina, and sodium sulphate dodecahydrate as nucleating agents. However, for building cooling applications PCM with minimal degree of supercooling, with the ability to release low enthalpy during discharging is an advantage.

Preparation and thermal properties of eutectic phase change materials (EPCMs) with nanographite addition for cold thermal energy storage

The main research objective of this paper is to develop a low-temperature Eutectic Phase Change Material (EPCM) for use in the Cold Storage Thermal Storage (CETS), with the aim of improving energy efficiency during the cold storage process and addressing energy crises and environmental concerns. In this study, capric acid, n-octanoic acid, and n-tetradecane are prepared as low-temperature EPCMs by melt blending, with the addition of nanographite to enhance their thermal conductivity. The thermal performance parameters, chemical stability, and thermal stability of the EPCMs under phase change cycles are tested and evaluated by using macroscopic experimental methods, DSC, FTIR, and infrared thermal imaging. The research results indicate that the G-2 low-temperature EPCM, prepared by mixing capric acid, n-octanoic acid, n-tetradecane, and nanographite with a mass ratio of 0.231:0.469:0.3:0.06, has optimal thermal properties, specifically including a melting point of 0.32 °C, a melting latent heat of 163.3 J/g, a thermal conductivity of 0.83 W/m·K, and an undercooling of 0.47 °C. These properties make it suitable for cold storage operations. Nanographite can effectively improve the thermal conductivity of EPCM, and a 6 % addition proportion can lead to a 417.45 % increase in thermal conductivity and a 64.39 % decrease in undercooling. However, once the content of nanographite exceeds 6 %, the stability of the EPCM will undergo a significant decline. Furthermore, the results of DSC, FTIR, and infrared thermal imaging confirm that capric acid, n-octanoic acid, n-tetradecane, and nanographite can be effectively co-melted with each other, the heat transfer framework function of nanographite improves the efficiency of latent heat utilization in EPCM, and the G-2 sample maintains acceptable chemical and thermal stability even after undergoing 200 phase change cycles.

Microstructure and mechanical properties of a first-generation single crystal superalloy CMSX-6

CMSX-6 alloy is a first generation of single crystal high temperature alloy and has been widely applied for the aeroengine and gas turbine blades. In the present study, the microstructure, tensile properties, stress rupture properties and fracture properties of the as-cast and heat-treated CMSX-6 alloy were investigated. The experimental results show that under the heat-treated condition the γ′ phase was about 0.5 μm, the volume fraction was about 66%, and the residual eutectic phase volume was 2%~5%. The tensile and stress rupture properties was similar that of the first generation of single crystal alloys, DD3 and DD407 developed by Beijing Institute of Aeronautical Materials and General Institute of Iron and Steel Research, China. And the results also indicate that CMSX-6 alloy has good fracture properties, oxidation resistance properties and corrosion resistance properties, and therefore CMSX-6 alloy has very good application prospect for the aeroengine and gas turbine blades materials.

Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in dilute α-magnesium

Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca, Mg-Sr and Mg-Ba systems. This investigation incorporated the difference in the ‘Work Function’ (ΔWF) measured via Kelvin Probe Force Microscopy (KPFM), as a property directly affected by interatomic bond types, i.e. the electronic structure, nanoindentation measurements, and Stacking Fault Energy values reported in the literature. It was shown that the nano-hardness of the solid-solution α-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba. Thus, it was shown, by also considering the nano-hardness levels, that SFE of a solid-solution is closely correlated with its ‘Work Function’ level. Nano-hardness measurements on the eutectics and ΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys. Correlation with ΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree, relatively simple atomic models and a number of assumptions. As asserted by this investigation, if the results of measurement techniques can be qualitatively correlated with those of the computational methods, it can be possible to evaluate the electronic structures in alloys, starting from binary systems, going to ternary and then multi-elemental systems. Our investigation has shown that such a qualitative correlation is possible. After all, the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level, that is, free electron density distributions. Our study indicated that the principles of ‘electronic metallurgy’ in developing multi-elemental alloy systems can be followed via practical experimental methods, i.e. ΔWF measurements using KPFM and nanoindentation.

Strengthening behavior and thermal conductivity of Cu/Al composite with penetration architecture

To improve the strength of Al alloys without severely deteriorating the thermal conductivity, the Cu/Al bimetallic composite comprising penetration architecture was artificially designed and fabricated via the additive manufacturing combined with the squeeze casting. The composite exhibited a good balance of the strength (∼340 MPa) and thermal conductivity (200 W/(m·K)), outperforming the traditional Al alloys. High thermal conduction is attributed to the geometrical Cu scaffold, which provides a rapid pathway for the electron conduction. Simultaneously, the good metallurgical bonding is attained by the formation of the Al2Cu eutectic phase along the interfaces, which effectively enhances the strength of the Cu/Al composite.

Investigation on indirect laser welding of copper to aluminum

Laser beam welding of aluminum (Al) to copper (Cu) is challenging due to the formation of intermetallic compounds that are brittle and have high resistivities. However, the Cu/Al phase diagram shows a region were solubility of Cu in Al is present and, on the other hand, a region with the formation of a eutectic phase between α-Al and Al2Cu is present as well. Targeting this area turned to be advantageous for solid state welding, as shown for probeless Friction-Stir-Spot-Welding realizing ductile joints between Al and Cu.In this paper an approach based on indirect laser welding of Cu with Al will be presented and discussed. A green laser was used in order to join Cu to Al in lap joint configuration. The laser beam irradiates the Cu surface, whereby the formation of a common melt pool between Cu and Al is avoided. The heat input and the temperature gradient are assumed to support diffusion at the interface between Cu and Al forming a near eutectic layer. Indeed, a melting layer is formed at the interface between Cu and Al supporting joint formation based on a firmly bonding between both materials. The solidified layer presents a copper rich area towards the copper sheet with plate-like structures of Al2Cu, a region with α-Al crystals on the aluminum side and a eutectic layer of lamellar Al2Cu and α-Al in between. The described morphology is very similar to investigations on probeless Friction-Stir-Spot-Welding, whereas a very low pressure is adopted in indirect laser welding and Al-oxide layer seems not to act as a barrier for joint formation.

Enhancement effect of Li addition on nitriding reaction and combustion of Al-Li alloy in N2

For aluminum-based alloy particles, the addition of alloying element lithium (Li) with the properties of a high chemical activity and a low melting/boiling point can significantly improve the thermo-reactive properties of aluminum (Al) particles. To further reveal the combustion mechanism, this paper presents the nitriding reaction and combustion characteristics of Al-Li alloy in nitrogen (N2) through thermogravimetric analysis and differential scanning calorimetry (TG-DSC) analysis at a low heating rate and laser-induced ignition experiments at a high heating rate, considering the influences of two kinds of Li contents (1.0 wt% @ Al-1.0Li and 2.5 wt% @ Al-2.5Li) on these characteristics and making a comparison to the counterpart Al. Al-Li alloy powders as-prepared by gas atomization method showed the texture of the Li-rich eutectic phase compounds on the surface by scanning electron microscope (SEM) characterization. The TG-DSC results demonstrated that the thermal nitriding reaction of Al-Li alloy in N2 was significantly faster than that of pure Al. The nitriding reaction temperature decreased from 853 °C for pure Al to 245 °C for Al-2.5Li alloy with a reduction of 71 %. The final weight gain of Al-2.5Li alloy was almost three times higher than that of pure Al in N2. The SEM photograph of intermediate nitriding products revealed that the cracks and loose “island” structures in the Li-rich zone on the Al-Li surface were the key to preventing the formation of a “passivation effect” into Al and promoting N2 uptake during melting. In addition, Li also acts as a catalytic carrier and “oxygen absorber” to enhance the Al-N reaction. The combustion of single Al-Li alloy microparticles induced by laser showed two stages: preheating and rapid nitriding. Al-Li alloy particles were ignited more rapidly and showed typical gas-phase / surface combustion modes different from pure Al. According to these findings, the combustion mechanism was proposed to help guide the development of Al-based solid propellants containing Li and the synthesis of AlN/Al composites in nitrogen-rich environments.

Castable eutectic Ni–Ce high temperature alloys strengthened by γ/γʹ microstructure

Ni-based superalloys are the premier material for high-temperature applications but are often difficult to manufacture via solidification-based processing. Eutectic alloys typically possess good castability due to narrow solidification ranges. The Ni–Ce system possesses a eutectic reaction but has never been examined as a potential high-temperature material. This work investigates the microstructure and mechanical properties of near-eutectic alloys Ni–17Ce and Ni–17Ce–5Al (wt.%). Both alloys show outstanding high-temperature microstructure and mechanical property stability at 900 °C. The formation of Ni3Al (γʹ) precipitates is observed in the primary FCC-Ni phase of the ternary Ni–Ce–Al alloy. The precipitation hardened ternary alloy exhibits superior hardness to Inconel 718 at elevated temperatures, retaining its strength to 750 °C, or about 50 °C higher than Inconel 718. The novel hierarchical microstructure consisting of thermally stable eutectic regions combined with γʹ-strengthened primary FCC-Ni and eutectic phases show great promise as a castable material solution for high-temperature applications.

Microstructure and property optimization of Al–8Ce alloys: Electromagnetic stirring and Sc–Zr microalloying

To further improve the strength of an Al–Ce alloy, the effects of electromagnetic stirring treatment, Sc–Zr microalloying, and their compound action on the microstructure and properties of the Al–8Ce alloy were investigated for the first time in this study. The results show that the primary α-Al becomes coarse, the eutectic Al11Ce3 phase is refined and the lamellar spacing increases significantly due to the combined effect of forced convection of electromagnetic field and dendrite fragmentation and nucleation in Al–8Ce alloy after electromagnetic stirring treatment. After the Sc–Zr microalloying treatment of the Al–8Ce alloy, the α-Al changes from a dendritic to fine round morphology, and the eutectic Al11Ce3 phase changes from lamellar to fibrous, which is due to the heterogeneous nucleation of Al3(Sc, Zr) phase and the adsorption refinement caused by the enrichment of Sc and Zr. The optimization effect of Sc–Zr microalloying on the mechanical properties of the Al–8Ce alloy was better than that of electromagnetic stirring and their synergistic treatment. The tensile strength and yield strength of Al–8Ce alloy with Sc–Zr additions were increased from 157 MPa to 85 MPa–192 MPa and 115 MPa, respectively, by 22.3 % and 35.3 %. After aging treatment, the tensile strength (from 192 to 272 MPa) and yield strength (from 115 to 221 MPa) significantly improved owing to the secondary precipitation of Al3(Sc, Zr) particles. The precipitation strengthening of the Al3(Sc, Zr) phase was the main contributor to the high yield strength of the alloy.

The Effect of Cycling Process Between −196 and 120 °C on Microstructure and Properties of Additively Manufactured 7050 Al Alloy

Wire arc additively manufactured (WAAM) aluminum alloys have been applied in the aerospace field. However, there was a lack of research on the stability of additive components under high‐ and low‐temperature cycling conditions in space. This study focuses on the evolution of microstructure, defects, and mechanical properties of WAAM 7050 aluminum alloy during high‐ and low‐temperature cycling from −196 to 120 °C. The number of cycles is 1, 2, 5, and 10, and one cycle time is 100 min. The results show that the number of η nanophases increase significantly after 5 cycles, and the η′ phases precipitate after 10 cycles. In defects, the porosity increases to 4 times of the as‐deposited state after 10 cycles, and the mean equivalent diameter of micropores is stabilized at 0.77 μm. In mechanical properties, the ultimate tensile strength decreases gradually with the increase of cycle times, and the hardness reaches the maximum of 143.2 HV after 5 cycles. The number of micropores increases after 10 cycles, and micropores have a weak effect on the failure mechanism. Cracks tend to sprout and expand along the eutectic phases and pores in the equiaxial grain zones, and equiaxial grain zones are the weak areas when they break.

Design and characterization of LaB6/NbNiTaTi refractory high-entropy alloy coatings: Effect of in-situ TaB phase on strengthening mechanism

The excellent strength and hardness obtained from the customized phase compositions provide vast spaces for surface protection application of refractory high entropy alloy (RHEA) coatings in titanium alloys. However, the introduction of high-strength brittle phase in RHEA coatings commonly increases the cracking tendency and affects their service life. In this work, we propose a design strategy to enhance the mechanical properties of RHEA coatings by introducing an extremely stable high strength boride combined with a ductile phase. Experimentally, LaB6/NbNiTaTi RHEA coatings mainly consist of BCC phase, in-situ TaB phase and NiTi/IM eutectic phase. TaB phase with high-density (110) nanotwins inside presents needle-like morphology with the long side axis parallel to the [001] direction. Excessive needle-like TaB phase is fully fused and fractured due to its preferential growth along a specific direction. The fracture surface analysis shows that BCC phase bears the main deformation, NiTi phase can relieve stress concentration at the boundary while bearing a small amount of deformation. By contrast, the low-density dislocation distribution and the low energy extended dislocation structure in TaB phase exhibit the phase stability. In addition, the amorphous islands are formed near the high-deformation regions when the defect concentration reaches the critical value.

Critical Role of In-Situ-Generated Eutectic Carbonates in Superstructured Solid Fuel Cells.

As a distinct type of fuel cell, a carbonate-superstructured solid fuel cell (CSSFC), which possesses excellent performance and easy fabrication as well as low cost, was recently invented by our group. Herein, we demonstrated the critical role of the in-situ-generated eutectic carbonate phase in CSSFC. Namely, the in-situ generation of eutectic Li2CO3/Na2CO3 system increased the oxygen ionic conductivity of Ce0.8Sm0.2O1.9 solid electrolyte by 20 times (from 3.5 × 10-3 to 7.3 × 10-2 S cm-1), leading to 6 times enhancement of CSSFC peak powder density (up to 206 mW cm-2) with methane fuel at 550 °C. This finding is extremely important for designing efficient CSSFCs.

The Effect of Fe Content on the Microstructure and Tensile Properties of Friction-Stir-Welded Joints in Recycled Cast Aluminum Alloy.

The presence of the impurity element Fe significantly influences the overall performance of recycled aluminum alloy. This study aims to elucidate the impact of Fe content on the microstructure and tensile properties of friction-stir-welded (FSW) joints in recycled cast A356 aluminum alloy. Three samples with varying Fe content were prepared for FSW joints. The quality of the weld zone was meticulously assessed through macrostructure and microstructure analyses. The tensile strengths of the joints were carefully evaluated and correlated with the microhardness and microstructure of the weld zone. The research findings reveal that, among the three fabricated joints, the one with an Fe content of 0.3 wt.% demonstrates the most favorable tensile performance. This particular joint exhibits the highest tensile strength of 153 MPa, commendable yield strength of 90 MPa, and a favorable elongation of 5.7%. The mechanisms responsible for grain refinement in the weld nugget zone involve plastic deformation and dynamic recrystallization. Significantly, the disruptive effects of friction-stir action on eutectic silicon phases and rich iron phases emerge as crucial factors contributing to the enhanced performance of the weld nugget zone in the welded joint.

Crevice Corrosion Initiation and Growth of Die-Cast ADC12 Aluminum Alloy

Die-cast ADC12 (Al-3Cu-10Si) aluminum alloy is widely used because of mechanical properties and castability. In atmospheric environments, crevice corrosion sometimes occurs on ADC12; therefore, improvement of corrosion resistance and elucidation of corrosion mechanisms are needed.As-cast specimens of ADC12 were used in this study. Pure Al sheets were used for comparison. The microstructure of ADC12 was composed of α-Al and Al-Si eutectic phases. Intermetallic particles (IMPs) containing Cu existed. IMPs containing Fe also existed. The size of IMPs was around 1 μm.Crevice was made between a polycarbonate nut and bolt, and immersion test was performed in 0.1 M NaCl. After immersion, the dissolution of α-Al was observed inside the crevice. To ascertain the effect of pH on α-Al phase dissolution, immersion test was carried out in 0.1 M HCl and 0.1 M NaCl (pH 10.0) In 0.1 M HCl, α-Al dissolved, and the corrosion morphology was similar to that inside the crevice.

Metallurgical Analysis in the Outer Tube Fault Area

In the automotive manufacturing industry, product failures are still found. In this study, one of the automotive components, namely the outer tube of the motorcycle front fork, was cracked. The outer tube is part of the shock absorber component which is also connected to the motorcycle steering system. Failure analysis aims to obtain some data or facts that can indicate the root cause of the failure or failure. Sample preparation which includes the process of selecting the cut area, cleaning and cutting for the fractography process. As for metallography, sample preparation is continued with the process of mounting, sanding, polishing and etching. Fractographic test showed that the fracture occurred in a brittle fracture mode, with no traces of plastic deformation. The morphology of the fracture surface also shows the presence of gas trapped in large quantities. In the metallographic test, the overall microstructure shows an eutectic phase with a uniform dendrite structure pattern, this indicates that metal solidification occurs quite quickly and can cause a lot of gas to be trapped in the metal characterized by the presence of multiple porosities. This can provide an indication of the relationship between the microstructure and the fracture surface morphology. Cracking and brittle fracture can be caused by the stress that occurs in the metal that exceeds the yield and plastic limits due to the large pressure of gas trapped in the metal.

Significantly enhanced fatigue resistance and mechanisms of hypoeutectic Al-Si composite calibrated using trace in-situ nanocrystals

Fatigue resistance under extreme stress conditions is an important indicator to evaluate industrial application potential of Al-Si-Mg alloys, but their fatigue resistance is inherently weakened by large grain size, long-needle Si phases and coarse precipitates. This work reports significantly optimized microstructure configuration and fatigue resistance of hypoeutectic Al-Si composite optimized by the nanocrystallization products of a NiNbTi metallic glass. It was proved the in-situ NiTi (B2) nanocrystals can serve as the heterogeneous nucleation sites of α-Al and β-Mg2Si and the growth retarder of eutectic Si. Particularly, the optimized composite exhibited nearly 5 times and 6 times longer fatigue life than the unoptimized alloy at 120 MPa (60 Hz) and 240 MPa (20 Hz), respectively. The fatigue strength (N = 107) was increased by 21.7 % and 25.9 % at 60 Hz and 20 Hz, respectively. The α-Al refinement enhanced the resistance to fatigue crack initiation. The refinement and spheroidization of eutectic Si phases reduced stress concentration. Also, the austenite-martensite phase transformation of NiTi afforded more energy for precipitation. Refined β-Mg2Si and β'' phases were facilitated to interact with dislocations, improving the resistance to dislocation slip during cyclic strain through the dislocation shearing effect. This work provides a theoretical basis for the future development of Al-Si alloys and composites with excellent fatigue resistance for expanding their industrial application scope.