High-speed Melt Spinning Research Articles

Strategy of refining the microstructure of Nd-Fe-Co-Ga-B ribbons by high-speed melt-spinning and annealing

• Increasing the melt-spinning speed to 50 m/s refines the grain size. • Changing the crystallization process is the mechanism of grain refinement. • The size of equiaxed grains in the annealed ribbons is reduced to 50–200 nm. • The intense exchange coupling effect contributes to the higher remanence. • The microstructure evolution models are proposed. Given the uneven grain size distribution in the ribbons melt-spun at 25 m/s, the strategy of improving the microstructure and magnetic properties of the ribbons by increasing the melt-spinning speed is discussed. The experimental results show that the grain size of Nd 13.65 Fe 73.55 B 5.6 Co 6.6 Ga 0.6 ribbons annealed at 700 °C is reduced to 50–200 nm by melt-spinning at 50 m/s. The change in the crystallization process is the primary mechanism for grain refinement. At high quenching speed, the amorphous matrix is formed first in the as-spun ribbons, and then uniform crystallization can be achieved through annealing. Compared to the annealed ribbons melt-spun at 25 m/s, the Mr and M 2T increased by ∼8 % due to the intense exchange coupling effect and the refined grains.

Verification of the Influence of Processing History through Comparing High-Speed Melt Spinning Behavior of Virgin and Recycled Polypropylene.

A ‘model’ material of recycled polypropylene (PP) was prepared through the injection molding process, and the effect of processing history on the polymer characteristics was investigated through the high-speed melt spinning of virgin and recycled PP. On-line measurement of the thinning behavior of the spin-line revealed the downstream shift of solidification point for the recycled PP at the take-up velocity of 1.0 km/min, indicating the suppression of flow-induced crystallization. The difference was not clear at higher take-up velocities of up to 5 km/min. For any identical take-up velocity, no clear difference in the stress-strain curves and birefringence of the fibers from virgin and recycled PP could be observed, whereas the detailed investigation on the variation of relative amount of c-axis and a*-axis oriented crystals in the fibers prepared at varied take-up velocities suggested the deterioration of flow-induced crystallization at 1.0 km/min. It was speculated that the processing history induced the lowering of the entanglement density, which affected the melt spinning and crystallization behavior. An undistinguishable difference between the virgin and recycled PP at increased take-up velocities suggested the existence of an optimum elongational strain rate for the detection of the different states of molecular entanglement.

Recyclability of Opaque PET from High Speed Melt Spinning: Determination of the Structures and Properties of Filaments.

Recycling opaque Polyethylene terephthalate (PET), which contains 1 to 10 wt % TiO2 submicron particles, has become of interest in the past few years. However, the bottle-to-fiber recyclability of opaque PET has not been assessed yet. In this work, opaque PET packaging has been characterized, and high-speed melt-spun filaments with different amounts of opaque PET (30–50–100%) blended with standard transparent recycled PET (rPET) have been produced in a pilot system. The opaque PET filaments produced have also been compared to a transparent rPET blend with masterbatch PET/TiO2 at different amounts of filler (1–3–6 wt %), produced with the same parameters. The structure-properties relationship of rPET melt-spun fibers has been investigated with crystallinity measurements, amorphous and crystalline phases orientation, and tenacity. It has been observed that the degree of crystallinity, the crystalline and amorphous phases orientation and the tenacity decreases with opaque PET addition and, to a lesser extent, with TiO2 addition. It has been suggested that TiO2 particles are not entirely responsible for the decrease in mechanical properties of opaque PET filaments since opaque rPET filaments have inferior properties to r-PET/TiO2 filaments at the same filler content.

The influence of silica aerogels on physical, mechanical, and morphological properties of melt-spun POY and DTY polyester yarns

Thanks to over 90 vol% air content, aerogels are the lightest known solid state materials with low thermal conductivity and high surface area. Aerogels are also suitable candidates in fibrous blankets, construction, and thermoset composites, while their fragile characteristic limits their application in thermoplastic composites so far. In this study, silica aerogel-filled polyester nanocomposite filaments were produced through high-speed melt-spinning after twin-screw extrusion of their nanocomposite compounds, containing 0.4, 1, 2 and 4 wt% filler contents. This approach is a solution for overcoming to the dusting problems in aerogel/fiber blankets, aiming in insulation or other application perspectives. The compounding and melt-spinning trials resulted in successful fiber production (except for 4 wt% filler content). Microscopic observations showed a solid cross-section for the fibers (24 μm in diameter) while the aerogels caused a rough surface for the nanocomposite fibers along with hydrophobic characteristic (high contact angle). BET analysis showed 90% porosity for as received aerogels and 63% for the aerogels after processing with polymer. In the same line, densitometry confirmed the partial porosity of the aerogels in masterbatches and nanocomposite fibers. Mechanical characterizations showed that the fibers have acceptable performance after the spinning process. Thermal analysis results confirmed the presence of aerogels within the fibers. These developed nanocomposite fibers are suggested for future evaluations to be considered in different applications.

Analysis of Necking Deformation Behavior in High-Speed In-line Drawing Process of PET by On-line Diameter and Velocity Measurements

Abstract To clarify the characteristic behavior of filament deformation in high-speed in-line drawing process of poly(ethylene terephthalate) (PET), on-line measurements of filament velocity and diameter were performed. In the process, velocity of the first godet roller was fixed at 2 km/min and the draw ratio was varied from 1.75 to 2.25 by changing the velocity of the second godet roller from 3.5 to 4.5 km/min. For comparison, on-line measurements were also performed for the high-speed melt spinning process at take-up velocities of 2 to 5 km/min. Diameter and velocity profiles of PET filament in the high-speed in-line drawing process indicated that the filament started to deform immediately after passing through the first godet roller (GR-1), and finished its deformation at 40 ~ 60 cm from the GR-1. The region of deformation became narrower and shifted toward the GR-1 with an increase in the draw ratio. Detailed analysis of necking deformation through simultaneous diameter measurements at two positions of close distance revealed that the position of necking deformation fluctuates along the drawing-line and its shape varies significantly depending on the direction of its movement. When the position of necking deformation was shifting toward the upstream, its shape was steeper than the one shifting toward the downstream. Results of the simultaneous on-line measurements of diameter and velocity supported this conclusion qualitatively. The analyzed maximum strain rate at the draw ratio of 2.0 reached a high value of 510 s– 1.

Structure development in high-speed melt spinning of high-molecular weight poly(ethylene terephthalate)/polypropylene islands-in-the-sea bicomponent fibers

High-speed melt spinning of island-in-the-sea (SI) type bicomponent fibers with 74 islands consisting of high-molecular-weight poly(ethylene terephthalate) (HMW-PET) and polypropylene (PP) was achieved. The structure and mechanical properties of the HMW-PET component (islands) in the SI fibers were significantly enhanced with increasing the take-up velocity, while those of PP component (Sea) were suppressed. These results were attributed to the concentration of spinning stress on the HMW-PET component exhibiting higher elongational viscosity in the spinline. Considerable interaction between the two components in the SI fibers contributed to uniform structure development of the island parts in the fibers and improvement of the melt structure in the spinline. These results further enhanced the mechanical property and spinnability of the island parts. The thermoplastic composites, manufactured using the high-speed spun SI fibers with the islands of fine diameter (approximately 1.9 μm), exhibited a high tensile strength of approximately 1.0 GPa by microfiber-reinforced effect.

Fiber Formation and Structural Development of HBA/HNA Thermotropic Liquid Crystalline Polymer in High-Speed Melt Spinning.

High-speed melt spinning of thermotropic liquid crystalline polymer (TLCP) resin composed of 4-hydroxybenzoic acid (HBA) and 2-hydroxy-6-napthoic acid (HNA) monomers in a molar ratio of 73/27 was conducted to investigate the characteristic structure development of the fibers under industrial spinning conditions, and the obtained as-spun TLCP fibers were analyzed in detail. The tensile strength and modulus of the fibers increased with shear rate in nozzle hole, draft in spin-line and spinning temperature and exhibited the high values of approximately 1.1 and 63 GPa, respectively, comparable to those of industrial as-spun TLCP fibers, at a shear rate of 70,000 s−1 and a draft of 25. X-ray diffraction demonstrated that the mechanical properties of the fibers increased with the crystalline orientation factor (fc) and the fractions of highly oriented crystalline and non-crystalline anisotropic phases. The results of structure analysis indicated that a characteristic skin-core structure developed at high drafts (i.e., spinning velocity) and low spinning temperatures, which contributed to weakening the mechanical properties of the TLCP fibers. It is supposed that this heterogeneous structure in the cross-section of the fibers was induced by differences in the cooling rates of the skin and core of the fiber in the spin-line.

Melt-Spun Fibers from Bio-Based Polyester-Fiber Structure Development in High-Speed Melt Spinning of Poly(ethylene 2,5-furandicarboxylate) (PEF).

Poly(ethylene 2,5-furandicarboxylate) (PEF) is regarded as a bio-based alternative or complementary polyester for the widely used fossil resource-based polyester, poly(ethylene terephthalate) (PET). High-speed melt spinning of PEF of low and high molecular weight (L-PEF, H-PEF) was conducted, and the structure and properties of the resultant as-spun fibers were investigated. The occurrence of orientation-induced crystallization was confirmed for the H-PEF at the take-up velocity of 6.0 km/min, the highest speed for producing PET fibers in the industry. Molecular orientation and crystallinity of the as-spun fibers increased with the increase of take-up velocity, where the H-PEF fibers always showed a higher degree of structural development than the L-PEF fibers. The tensile modulus of the high-speed spun H-PEF fibers was relatively low at 5 GPa, whereas a sufficiently high tensile strength of approximately 500 MPa was measured. These values are adequately high for the application in the general semi-engineering fiber field.

Dyeing Behavior and Multi-Functionalities of Polylactide/Poly (Ethylene Terephthalate) Conjugate Fibers Produced by High-Speed Melt-Spinning

Various types of conjugate fibers comprised of polylactide (PLA) and polyethylene terephthalate (PET), with their blend in the sheath, PET as the core, were produced by high-speed melt-spinning. Due to the higher glass transition temperature of PET, the orientation-induced crystallization only occurred in the PET core. The crystalline and continuous PET core of the conjugate fibers effectively suppressed the shrinkage during dyeing, even in a pressurized water bath at 130 °C comparable to the commercial level, to less than 5% while achieving a color strength higher than 15. Post-annealing in the restrained mode could effectively cause the fine PET fibrils embedded in the sheath to rise out from the surface of the fibers during dyeing by the sliding friction force between the fibers. The PET fibrils rising out from the sheath were strong enough and showed an entangling behavior which would be useful to fabricate non-woven fabrics. The amorphous PLA domains exposed on the fiber surface showed the bacteriostatic activity valuable for the inhibition of the formation of biofilms.

Fiber Structure, Tensile Behavior and Antibacterial Activity of Polylactide/Poly(butylene terephthalate) Bicomponent Fibers Produced by High-Speed Melt-Spinning

Various types of bicomponent fibers composed of polylactide (PLA) and poly(butylene terephthalate) (PBT) with different molecular weights, arranging the polymers separately in the skin or core, were produced by high-speed melt-spinning. The bicomponent spinning, arranging the PLA with high molecular weight (melt flow rate =1.9 g/10 min, L-lactide content = 98.7%) in the skin and the PBT with low molecular weight (IV = 0.835–0.865 dL/g) in the core, resulted in orientation-induced crystallization in the PLA component at the spinning speed of 2 km/min. This crystallization effect was ascribed to a chain-extending treatment applied to the original PLA (MFR = 4.0 g/10 min) to increase its molecular weight. By the treatment the PLA could crystallize when spun even at 1 km/min in its single-component spinning. On the other hand, the bicomponent spinning system interfered with the orientation-induced crystallization of PBT in the core. As a result, the critical spinning speed needed to generate the orientation-induced crystallization in the core PBT was elevated to 4 km/min. The inferior tensile behavior of the bicomponent fibers, as compared to the single-component PLA or PBT fibers, suggested poor compatibility between PLA and PBT. Transesterification reactions rarely occurred at the interface of the two polymers. The bicomponent fibers prepared from high molecular weight PLA and low molecular weight PBT, however, showed sufficient antibacterial activity and physical properties to be suitable for designing medical clothing materials.

Influencing factors on the amorphous phase formation in Fe–7.7 at% Sm alloys solidified by high-speed melt spinning

The metastable SmFe12 stoichiometric compound has been reported to have superior magnetic properties to the traditional Nd2Fe14B intermetallic compound that can be massively produced by the widely used melt-spinning technique. However, there have been no reports on the successful synthesis of the bulk metastable SmFe12 or amorphous phase with the composition of Fe–7.7 at% Sm (the SmFe12 phase composition) via the aforementioned technique. In the present study, the binary Fe–7.7 at% Sm melt was spun onto a high-speed single Cu roller under various processing conditions. The influencing factors, e.g., the diameter of the nozzle orifice, the ejection gas pressure, and the species of the chamber gas, were examined to clarify the production condition of the amorphous ribbon. It has been confirmed that the careful control of the processing conditions enables the binary Fe–7.7 at% Sm melt to be spun into amorphous ribbons. Based on the in-situ observation of a high-speed video (HSV) camera, a simple model that illustrates the separation of the ribbon from the melt reservoir was proposed, from which the cooling curves of ribbons with different thickness were calculated. Further analysis indicated that both the model and the numerical calculation results agree well with the high resolution TEM observations near the free surface and the roller sides in terms of the structure formation.

Effect of Polycondensation Catalyst on Fiber Structure Development in High-Speed Melt Spinning of Poly (Ethylene Terephthalate).

We conducted a preliminary study on fiber structural development in the high-speed melt spinning of environmentally friendly polyethylene terephthalate (Ti-PET) synthesized with 25 ppm of titanium-based catalyst, which was compared with conventional PET (Sb-PET) synthesized with 260 ppm of antimony-based catalyst. Gel permeation chromatography of Ti- and Sb-PET resins of intrinsic viscosity 0.63 confirmed that both resins have similar molecular weights and distributions. However, differential scanning calorimetry revealed that the Ti-PET resin exhibited a lower melt–crystallization peak and isothermal melt-crystallization rate than the Sb-PET resin. High-speed melt spinning of the Ti- and Sb-PET was possible up to a spinning velocity of 6 km/min. Two-dimensional wide-angle X-ray diffraction analyses showed that the molecular orientation of the obtained as-spun Ti- and Sb-PET fibers increased with spinning velocity, and a highly oriented, crystalline structure by orientation-induced crystallization started to appear from 5 km/min. Notably, Ti-PET fibers showed a lower degree of crystalline structural development and lower tensile strength compared with Sb-PET fibers under the high-speed spinning conditions. Our results suggest that the catalyst in PET resins can act as nucleating agents in thermal- and orientation-induced crystallization, and that differences in catalyst content can influence PET fiber structure development under extreme conditions in high-speed melt spinning.

High-Speed Melt Spinning of Polylactide/Poly(Butyleneterephthalate) Bicomponent Fibers: Mechanism of Fiber Structure Development and Dyeing Behavior

Bicomponent fibers consisting of polylactide (PLA) as the sheath and poly(butylene terephthalate) (PBT) as the core were produced by high-speed spinning to obtain materials suitable for medical clothing. The higher-order structure of the PLA fiber component appeared to exhibit simple, alternately stacked, uniaxially oriented amorphous and crystalline regions. Therefore, fairly large tanδ peaks were observed for single-component PLA fibers, even when the orientation-induced crystallization was achieved by high-speed spinning. By conjugating PLA with PBT, although limited mutual interference with the crystallization of each component occurred, both the PLA (Mw = 170,000, L-lactide content = 98.7%) and PBT (intrinsic viscosity = 0.835-0.865 dL/g) could crystallize on a high-speed spinning line, and the proposed formation of a shish-kebab-like structure in the PBT component enhanced the thermal stability of the bicomponent fibers, particularly resulting in shrink-proof properties. The bicomponent fibers developed herein could be deeply dyed at 98 °C, with results comparable to those of industrial polyester, and peeling of the PLA skin layer was rarely observed, even when the dyed fibers were flattened by a rubbing force.

Poly(l-lactide) and Poly(l-lactide- co-trimethylene carbonate) Melt-Spun Fibers: Structure-Processing-Properties Relationship.

l-Lactide/trimethylene carbonate copolymers have been produced as multifilament fibers by high-speed melt-spinning. The relationship existing between the composition, processing parameters and physical properties of the fibers has been disclosed by analyzing how the industrial process induced changes at the macromolecular level, i.e., the chain microstructure and crystallinity development. A poly(l-lactide) and three copolymers having trimethylene carbonate contents of 5, 10 and 18 mol % were synthesized with high molecular weight ( Mn) up to 377 kDa and narrow dispersity. Their microstructure, crystallinity and thermal properties were dictated by the composition. The spinnability was then assessed for all the as-polymerized materials: four melt-spun multifilament fibers with increasing linear density were collected for each (co)polymer at a fixed take-up speed of 1800 m min-1 varying the mass throughput during the extrusion. A linear correlation resulted between the as-spun fiber properties and the linear density. The as-spun fibers could be further oriented, developing more crystallinity and improving their tensile properties by a second stage of hot-drawing. This ability was dependent on the composition and crystallinity achieved during the melt-spinning and the parameters selected for the hot-drawing, such as temperature, draw ratio and input speed. The crystalline structure evolved to a more stable form, and the degree of crystallinity increased from 0-52% to 25-66%. Values of tensile strength and Young's modulus up to 0.32-0.61 GPa and 4.9-8.4 GPa were respectively achieved.

Melt-spun PLA liquid-filled fibers: physical, morphological, and thermal properties

PLA hollow fibers with different internal diameters were produced as a media for liquid encapsulation via high-speed melt-spinning process, changing important parameters (e.g. material type, polymer throughput, extrusion temperature, quench flow rate, drawing ratio, and winding speed). Morphological analysis showed 300% increment (linear mode) for internal and outer diameters by increasing the polymer throughput from 14.6 to 87.6 ml/min while raising the winding speed from 500 to 1500 m/min resulted in decreasing 70 and 75% for internal and external diameters, respectively. Quench flow rate and extrusion temperature showed lower effect on just internal diameter. XRD patterns indicated that using higher drawing ratio led to increase in the fiber crystallinity. According to the physical studies, although the linear density was duplicated about 10 times by increasing the polymer throughput, but the winding speed reduced 300%. Adding the polymer throughput, as the main factor, caused the tensile strength, elongation at break, modulus, tenacity, and fracture toughness to be changed approximately +650%,+217%, –68%, –58%, and +1500%, respectively. Other parameters also influenced (described in text) on tensile performances. Thermal analysis showed lower thermal stability for the fibers extruded at higher temperature. DSC results also confirmed the same trend in the degree of crystallinity of the melt-spun fibers. Melt-spun fibers were filled with glycerol as a model liquid using the previously developed microfluidic approach. Biodegradable liquid-filled fibers were conducted on composting test. Successful biodegradation is a promising result for potential applications such as agriculture pesticide and medical drug delivery.

Melt-spun Liquid Core Fibers: A CFD Analysis on Biphasic Flow in Coaxial Spinneret Die

Simulation of co-flowing behavior in a coaxial geometry (based on the designed spin pack) has been performed using properties of two immiscible liquids to represent flowing regime while passing through the spinneret for production of liquid core fiber (LCF) by one single step high-speed melt-spinning process. Computational Fluid Dynamics (CFD) simulations confirmed the continuous liquid core channel, obtained in bicomponent melt-spinning of LCF. Also different interface morphologies could be observed: from jetting to dripping and transition core-annular regime, based on the simulation parameters, affecting the driving forces. Results showed different co-flow regimes by systematic variation in nondimensional parameters (flow rate ratio, viscosity ratio, Reynolds number, Weber number and Capillary number), individually. Also diameter of the core liquid is reduced in a logarithmic mode by increasing the outer liquid’s flow rate. Flowing morphologies at different conditions were plotted in 2D state diagrams, illustrating transition from dripping to jetting regime by changing two different parameters. This CFD analysis bears potential for simple ways of controlled jet breakup in microfluidic devices, which currently primarily rely on Rayleigh-Taylor breakup. Notably this work highlights the melt-flow regime in the spinneret to realize developed fiber core structures at different conditions during bicomponent melt-spinning. Using various materials with different properties in liquid core fiber production promises many applications for this new generation fiber in very near future.

Analysis of Multiple Melting of High-Speed Melt Spun Polylactide Fibers Based on Kinetic Modeling

ABSTRACTMultiple melting behavior of high-speed melt-spun polylactide (PLA) fibers was investigated by temperature modulated differential scanning calorimetry (TMDSC) in the heating process with various modulation periods in the calorimeter. In the case of the as-spun PLA fibers taken-up at 1 km/min, a melting endothermic peak and a recrystallization exothermic peak appeared at the same peak temperature of 151°C in the reversing and non-reversing heat flows (RHF and NRHF), respectively, whereas at 168°C, an endothermic peak was observed in both the RHF and NRHF. On the other hand, the as-spun PLA fibers taken-up at a high-speed of 6 km/min showed the melting in both the RHF and NRHF, but the recrystallization behavior was not obvious in the NRHF at the shorter modulation period conditions. The obtained data were analyzed based on the kinetic modeling of melting proposed by Toda et al. The real and imaginary parts of the complex apparent heat capacity in the melting region showed a strong modulation period dependence for both the low- and high-speed spun fibers. The endothermic heat flow of melting was separated by extrapolating the frequency to zero. For the PLA fibers spun at 1 km/min, a set of melting and recrystallization peaks in the RHF and NRHF appeared even for the melting at 168°C. In other words, the simultaneous occurrence of melting and recrystallization was confirmed through this extrapolation. For the 6 km/min PLA fibers, the presence of an exothermic heat of recrystallization was clearly confirmed at a peak temperature of 164°C.

Differentiation of molecular chain entanglement structure through laser Raman spectrum measurement of High strength PET fibers under stress

The aim of this study was to investigate the mechanism for the improvement of mechanical properties of poly(ethylene terephthalate) (PET) fibers based on the concept of controlling the state of molecular entanglement. For this purpose, five different PET fibers were prepared through either the conventional melt spinning and drawing/annealing process or the high-speed melt spinning process. In both cases, the melt spinning process was designed so as to realize different Deborah number conditions. The prepared fibers were subjected to the laser Raman spectroscopy measurement and the characteristics of the scattering peak at around 1616 cm−1, which corresponds to the C-C/C=C stretching mode of the aromatic ring in the main chain, were investigated in detail. It was revealed that the fibers drawn and annealed after the melt spinning process of lower Deborah number showed higher tensile strength as well as lower value of full width at half maximum (FWHM) in the laser Raman spectrum. Narrow FWHM was considered to represent the homogeneous state of entanglement structure, which may lead to the higher strength and toughness of fibers because individual molecular chains tend to bare similar level of tensile stress when the fiber is stretched. In case of high-speed spun fibers prepared with a high Deborah number condition, the FWHM was narrow presumably because much lower tensile stress in comparison with the drawing/annealing process was applied when the fiber structure was developed, however the value increased significantly upon applying tensile load to the fibers during the laser Raman spectrum measurement. From these results, it was concluded that the Laser Raman spectroscopy could differentiate molecular chain entanglement structure of various fiber samples, in that low FWHM, which corresponds to either homogeneous state of molecular entanglement or lower level of mean residual stress, and small increase of FWTH upon applying tensile stress are considered to be the key factors for the improvement of the mechanical properties of PET fibers.

Preparation of antimicrobial fabric using magnesium-based PET masterbatch

The magnesium-based antimicrobial polyethylene terephthalate (PET) masterbatch (MAPM) was extruded from twin screw extruder by melting-and-mixing method, using magnesium-based antimicrobial agent (MAA) as the functional material for the first time. The magnesium-based antimicrobial fabric (MAPF) was prepared using MAPM and pure PET resin by high-speed melt-spinning technology and weaving technology for the first time. The materials used in this work were healthy to human body and friendly to environment. The characteristics of MAA, MAPM and MAPF were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When the MAPM (MAA) content reached to 25wt.% (5wt.%) in MAPF, the MAA had excellent dispersion and compatibility in MAPF, and the MAPF had good physico-mechanical properties. Then the MAPF presented excellent spinnability and antimicrobial property against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Candida albicans (C. albicans) and Aspergillus niger (A. niger), with pretty good laundering durability.

Enhanced grain refinement of in situ CeB6/Al composite inoculant on pure aluminum by microstructure control

In situ CeB6/Al composite has been proven to be an effective refiner for commercial pure aluminum, however, it remains unclear as to the mechanisms of synthesis and grain refinement. We use low-temperature alloying and high-speed melt spinning to optimize the microstructure of CeB6. It is found that in situ CeB6/Al composite shows controllable microstructure and its refining effect is obviously dependent on the size of CeB6 particle/cluster. As nano-CeB6 particles self-assemble into submicron clusters, the inoculant shows significantly enhanced refining effect, reducing the grain size of pure aluminum to ∼110 μm. The refining mechanism is attributed to the combining effect of the cluster structure in submicron scale and the excellent crystallography matching relationship of CeB6 and Al. Mechanical properties of pure aluminum are also improved by addition of in situ CeB6/Al composite inoculant due to collaboration effect of dispersion strengthening and grain refining strengthening.