Formation Of Grain Structure Research Articles

Comparative Study on Mechanical Properties and Microstructure Evolution of Mg-3Zn-1Mn/Sn Alloy through Ca-La-Ce Addition.

This study systematically investigates the influence of the composite addition of Ce, La, and Ca elements on the microstructure evolution and mechanical properties of Mg-3Zn-1Mn/Sn (wt.%) alloys. It indicates that the strength of Mg-Zn-Mn series alloys is superior to that of Mg-Zn-Sn series alloys, due to the stronger restriction of nanosized Mn particles on the recrystallization process and grain growth compared with Mg2Sn phases. The addition of the Ca-La-Ce elements significantly enhances the strength of the Mg-3Zn-1Sn alloy (YS increased by approximately 92.5%, UTS increased by approximately 29.2%, and EL decreased by nearly 52.2%), while for the Mg-3Zn-1Mn alloy, a balanced effect on both the strength and performance can be achieved. This difference mainly lies in the more pronounced refined effect on the grain size and the formation of a bimodal grain structure with strip-like un-DRXed grains and surrounding fine DRXed grains for the Mg-3Zn-1Sn alloy. In contrast, the addition of the Ca-La-Ce elements has a less obvious hindrance on the recrystallization process in the Mg-Zn-Mn series alloy, while significantly weakening the extrusion texture while refining the grains. Through in-depth characterization and experimental analysis, it is found that Sn and Ca can promote the formation of brittle and fine secondary phases. A nanoscale Sn phase (Mg2Sn phase) is more likely to accumulate at the grain boundaries, and the size of the nanoscale Ca2Mg6Zn3 in Mg-Zn-Mn series alloys is finer and more dispersed than that in Mg-Zn-Sn series alloys, thus strongly hindering recrystallization and refining the recrystallized structure of the alloy.

A novel strategy to achieve uniform ultrafine grains in Mg-Al-Sn-Ca alloy via pre-twinning combined with differential-thermal asymmetric extrusion

Obtaining fine grains with weak textures is an efficacious way of simultaneously improving the strength and ductility of magnesium (Mg) alloys. In this paper, an Mg-Al-Sn-Ca alloy with uniformly ultrafine grains and a weak texture has been prepared via pre-twinning followed by differential-thermal asymmetric extrusion (DAE). The alloy exhibits good strength and ductility (ultimate tensile strength: ∼381 MPa; elongation: ∼22 %). The results show that {102} tensile twins significantly promote dynamic recrystallization (DRX) during DAE, which beneficial for the formation of uniform fine grain structure and weak bimodal texture. This research provides valuable insights and methods for tailoring excellent mechanical properties of Mg alloys, facilitating their practical application in various engineering scenarios.

Radiation Effects in Tungsten and Tungsten-Copper Alloys Treated with Compression Plasma Flows and Irradiated with He Ions.

The paper presents the results of studying the structure and phase state of tungsten and tungsten-copper alloy after pulsed action of compression plasma flows and irradiation with helium ions. The compression plasma flows were used to modify the surface layer of tungsten, as well as to create an alloy based on tungsten and copper. Using scanning electron microscopy and X-ray structural analysis, the formation of radiation defects on the tungsten surface was detected in the form of local areas of exfoliation and destruction, which begin to form at helium ion irradiation doses of 2 × 1017 cm-2. It is shown that preliminary plasma treatment of the surface in the melting mode leads to the complete disappearance of surface radiation defects up to a dose of 2 × 1017 cm-2, which may be associated with the formation of a fine-crystalline grain structure, the intergranular boundaries of which serve as effective sinks for primary radiation defects.

Synchronous improvement in strength and ductility of Cu-bearing stainless steels through formation of bimodal grain structure induced by short-time electric pulses

Excellent strength and favorable formability are two important mechanical properties of stainless steel, but there is usually a trade-off between both properties. However, it has been suggested in recent studies that preparing microstructures with a non-homogeneous structure can effectively achieve strength-ductility synergy. Given these facts, a microstructure with bimodal grain structures was prepared in this study by short-time electric pulse treatment (EPT). Besides, the evolution of microstructures and mechanical properties of Cu-bearing stainless steel during EPT was analyzed. The results demonstrated that the non-uniform heating in the EPT process can rapidly promote localized grain growth, thus forming a bimodal grain structure compared with conventional heat treatment. The microstructure of the fine grains formed random textures, while the coarsened grains showed stronger textures. After EPT, the amount of S {123} < 634 < 634 >-type textures increased significantly, with the proportion reaching up to 30.1 %. There was also a certain amount of brass {110} < 112 >- and copper {112} < 111 >-type textures. Compared with the solution-treated samples, the best overall mechanical properties were detected under the optimal electric pulse parameters, which ultimately realized a synergistic increase of 11.8 % and 10.2 % in the ultimate tensile strength and ductility. The excellent strength-ductility synergy was closely related to heterogeneous deformation-induced (HDI) strengthening and textures induced by the bimodal grain structure. This finding may provide novel insights for enhancing the formability of biomedical metallic materials.

Effects of Zr, Al, and Al+Zr Addition on Phase Evolution Characteristics and Strengthening Mechanisms of Fe‐42Ni‐2Y2O3 Oxide Dispersion Strengthening Steels Developed by Mechanical Alloying and Spark Plasma Sintering

In the present study, Fe‐42 wt% Ni‐2 wt% Y2O3 super‐invar‐based steels have been explored to study the effects of Zr, Al, and Zr+Al addition on phase evolution, strengthening mechanisms, and mechanical behavior. Three different compositions, such as Fe‐42Ni‐2Y2O3‐2Zr (2YZr), Fe‐42Ni‐2Y2O3‐2Al (2YAl), and Fe‐42Ni‐2Y2O3‐2Zr‐2Al (2YAlZr), are developed by mechanical alloying (MA) followed by spark plasma sintering (SPS) at 1100 °C with an applied pressure of 60 MPa. The 2YZr alloy after SPS shows the evolution of a uniform grain size of ≈1.7 μm, whereas 2YAl reveals the formation of bimodal grain structure sintered under the same condition. Conversely, the combined effect of Al and Zr addition results in the evolution of ultrafine grained structure (≈380 nm) after SPS at the same condition (i.e., at 1100 °C). The superior mechanical strength of the 2YAlZr alloy (5.3 GPa/1415 MPa) is attributed to the evolution of uniformly dispersed extremely fine (60 nm) high‐density Al‐ and Zr‐rich oxide complexes in the ultrafine grained matrix. The analysis of strengthening contributions to the yield strength is found to be correlated well with the experimental results and attributed to the morphology of microstructural constituents, their stability, and volume fraction of dispersoids in the matrix.

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.

Achieving bimodal grain structure in Incoloy 945 nickel-based alloy through precipitation control

The Incoloy 945 nickel-based corrosion-resistant alloy was subjected to a low-temperature solid solution with a two-step aging process to fabricate a bimodal grain structure. The study investigated the mechanism behind the formation of the bimodal grain structure and its impact on mechanical properties. The results show that numerous clusters of fine grains, with an average size of 4 μm, were formed among the normal grains, which had an average size of 23 μm. The precipitation behavior in fine-grain clusters differs from that in normal grains. A high density of rod-like δ phases tends to precipitate inside refined grains. The inhomogeneous precipitation of δ phases is the main reason for the formation of fine-grain clusters because they have a strong ability to pin the grain boundaries for the growth of new recrystallized nuclei. The morphology of γ’ varies from short rod-like particles to spherical particles depending on their location in fine-grain clusters or normal grains. The difference in precipitation and grain structure leads to different deformation mechanisms in the two regions. The bimodal grain structure results in higher strength and work hardening rate during tension. The quasi-in-situ tensile test indicates that slip transfer is more easily induced in fine-grain clusters. Fine grains had an advantage in accumulating necessary geometric dislocations during deformation, resulting in a high work hardening rate for this bimodal grain structure sample.

Flash sintering can induce an anisotropic microstructure in ceramics. A phase field modeling insight

Field-assisted sintering techniques are at the forefront of advanced energy-saving procedures to create fully dense ceramic materials. At present, there is an extraordinary interest in understanding the sintering process and effectively controlling the final specimen's microstructure. This latter aspect is critical, but unfortunately, the short sintering times and intense electric fields under non-equilibrium conditions prevent a rigorous prediction in most cases. This paper is a theoretical contribution to gain insight into an outstanding effect of applying intense electric fields: the formation of non-spherical grain structures. A phase field simulation approach has been carried out to reproduce and determine the origin of this effect. The final simulated microstructures are proved to be textured. These results are explained in the framework of a recent model and compared with experimental evidence reported in the literature.

Exploring the influence of pin geometry on metallurgical and mechanical characteristics of dissimilar aluminum TIG welds via friction stir processing

This study explored the effect of friction stir processing (FSP) on tungsten inert gas (TIG)-welded AA6061-T6 and AA7075-T6 joints by utilizing three different tool pin geometries, namely simple cylinder (SC), threaded cylinder with triflat faces (THF), and simple square (SS). The metallurgical aspects of unprocessed and processed weld regions were analyzed and correlated with the ultimate tensile strength, impact toughness, and microhardness properties. Results revealed that the post-FSP with a THF pin transformed the coarse dendritic structures (AGS of 34.55 µm) of the TIG weld into equiaxed fine structures (AGS of 3.51 µm) and increased the UTS, impact toughness, and microhardness by 71.51%, 95.40%, and 72.46%, respectively. The joint processed with the THF pin resulted in the highest ultimate tensile strength of 279 MPa, impact toughness of 15.02 J, and microhardness of 116.13 HV in the nugget region compared to the other two pin geometries. The highest joint properties of THF pin were attributed to the formation of fine grain structures in the nugget region, high effective strain and heat generation, improved material flow, and the decimation of intermetallic precipitates with their uniform dispersion in the nugget region. The tensile fractured surface of the TIG weldment had noticeable macro voids and coarse dimples with some rough cleavage facet in the fusion region, resulting in a brittle mode of failure. However, the tensile fractured surface of TIG + FSP weldments showed ductile failure due to the presence of fine and deep dimples with tear ridges without any void.

Improvement of micro/nano-structure and corrosion resistance of TiCu alloy by addition of tin and their Sr-hydroxyapatite coating

This study explores the influence of tin (Sn) content on the properties of Ti7CuXSn (X = 2, 7, and 15 wt%) alloys, in both as-cast and heat-treated conditions. The investigation reveals that an elevated Sn content within the Ti7Cu alloy results in the formation of finer grain structures. Rapid quenching processes lead to the development of an ultrafine martensitic structure and the formation of (Ti,Sn)2Cu intermetallic compounds within the Ti7CuXSn alloys. Subsequent heat treatment processes induce the transformation of the ultrafine martensitic structure into a coarser one, accompanied by an increase in the volume fraction of (Ti,Sn)2Cu. X-ray diffraction (XRD) analysis validates the presence of α/α'-Ti(Sn,Cu) phases and (Ti,Sn)2Cu intermetallics across all alloy compositions. The Ti7Cu15Sn alloy demonstrates higher microhardness, primarily attributed to its smaller grain size, reduced lamellar spacing, and increased volume fraction of (Ti,Sn)2Cu. Furthermore, all specimens exhibit heightened microhardness following heat treatment due to the martensitic structure with heterogeneous and homogeneous nucleation of (Ti,Sn)2Cu intermediate growth. Electrochemical analysis reveals an enhanced corrosion resistance in the Ti7Cu15Sn alloy, attributed to its elevated Sn content. Nonetheless, the as-cast Ti7Cu15Sn alloy displays superior corrosion resistance, albeit with a marginal reduction in electrochemical performance following heat treatment. Surface characterization signifies the formation of a uniform oxide film, underscoring commendable corrosion resistance in both as-cast and heat-treated Ti7CuXSn alloys. Additionally, the study investigates the deposition of strontium (Sr)-doped ceramic coatings on as-cast Ti7Cu15Sn alloys. It is demonstrated that higher current density parameters yield denser and more crystalline Sr-HA coatings. Energy dispersive spectroscopy (EDS) mapping confirms the successful incorporation of Sr into the coating, showcasing its potential for applications in the field of biomedicine. Thus, this investigation highlights the significant impact of Sn content on microstructural refinement, enhancements in mechanical properties, and improved electrochemical performance within Ti7CuXSn alloys. These findings offer valuable insights for the design and optimization of alloy performance in diverse applications.

Nanocatalysis MoS2/rGO: An Efficient Electrocatalyst for the Hydrogen Evolution Reaction.

In this study, a systematic investigation of MoS2 nanostructure growth on a SiO2 substrate was conducted using a two-stage process. Initially, a thin layer of Mo was grown through sputtering, followed by a sulfurization process employing the CVD technique. This two-stage process enables the control of diverse nanostructure formations of both MoS2 and MoO3 on SiO2 substrates, as well as the formation of bulk-like grain structures. Subsequently, the addition of reduced graphene oxide (rGO) was examined, resulting in MoS2/rGO(n), where graphene is uniformly deposited on the surface, exposing a higher number of active sites at the edges and consequently enhancing electroactivity in the HER. The influence of the synthesis time on the treated MoS2 and also MoS2/rGO(n) samples is evident in their excellent electrocatalytic performance with a low overpotential.

Inertia radial friction welding of Ti60(near-α)/TC18(near-β) bimetallic components: Interfacial bonding mechanism, heterogenous microstructure and mechanical properties

Inertia friction welding has emerged as a promising technique for fabricating lightweight and high-strength components in aerospace industry. To achieve high-quality weldments between dissimilar titanium alloys, this present work systematically investigates Ti60 (near-α)/TC18 (near-β) bimetal components manufactured by inertia radial friction welding. The focus is on understanding the joint interface behavior, heterogenous grain structure, microstructural evolution and resulting mechanical properties, with a particular emphasis on dynamic recrystallization, phase transformation and atomic diffusion of elements in the welded zone and thermos-mechanical affected zone. The results revealed that the significant influence of thermo-physical property mismatch between the dissimilar workpieces (Ti60-Ring and TC18-Core) on the microstructure and tensile strength of the joints. This mismatch could be effectively controlled by setting different flywheel kinetic energy (Ek) before welding. The tensile strength of the Ti60/TC18 joints manufactured with levels of Ek ranging from 174.74 kJ to 207.95 kJ, were observed to be governed by the combined effect of mechanical interlocking, grain boundary strengthening, precipitation strengthening and hetero-deformation induced strengthening. The formation of heterogeneous grain structure and intergrowth grains on the Ti60 alloy side, and the dislocation tangles in the “forked” α phase of the TC18 alloy side are identified as key factors in achieving optimized bonding strength for dissimilar Ti60/TC18 bimetallic inertia radial friction welding.

Stability of the B2 ↔ B19′ martensitic transformation on thermal cycling of Ti-Hf-Ni-Cu thin ribbons

The B2 ↔ B19′ martensitic transformation was studied on thermal cycling of the Ti40.7Hf9.5Ni49.8-xCux (x = 5, 10 at.%) thin ribbons. The temperatures, as well as the enthalpy of the transformation, were found to be stable on thermal cycling. The stability of the B2 ↔ B19′ transformation was attributed to the formation of a specific grain structure during the crystallization of the initially amorphous ribbons. The grains were characterized by an average size of 800 nm, which increased the yield limit for dislocation slip to 700 MPa. Moreover, one martensite corresponding variant pair (CVP) formed on cooling inside each grain. It was assumed that the formation of one CVP martensite plate within the grain on cooling, as well as a high yield limit for dislocation slip, might have been responsible for the stability of the martensitic transformation temperatures and enthalpy on thermal cycling.

Tunable electrical and impedance characteristics of Co–Zn doped M-type Sr Hexaferrites: Role of grain, grain boundaries, electrical transport mechanisms and software/circuit modeling

M-type hexaferrites SrCoxZnxFe12-2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been synthesized using the sol-gel method. The structural, dielectric, and electrical properties of Zn2+ and Co2+ substituted strontium ferrite have been carried out. The dielectric and electric properties of prepared hexaferrites have been examined over the frequency range of 100 Hz to 2 MHz. The formation of the hexagonal phase has been confirmed by the X-ray diffraction (XRD) analysis. The substitution of Co2+ and Zn2+ causes a reduction in crystallite size from 39.50 to 26.42 nm being the smallest in the case of x = 1.0. Scanning electron microscopy (SEM) indicates the formation of honeycomb-like grain structures in composition x = 1.0. The dielectric spectrum shows that the dielectric constant and loss tangent vary non-monotonically with the doping of Co–Zn content. A non-Debye type relaxation is shown by the electric modulus of the prepared compositions. There is a reduction in relaxation time with the increase in doping of Co–Zn. The impedance spectra indicate the effects of both grain and grain boundaries on the electrical properties. The impedance analysis has been presented with the modeling of electrical processes in the samples using an equivalent circuit model comprising of parallel RC circuit for grains and grain boundaries. The obtained simulated results are in agreement with the measured results.

Low-temperature high-speed extrusion of a multicomponent Mg–Bi base alloy and its heat resistance during hot tension

In this work, the microstructure and room/high-temperature (RT/HT) mechanical properties of Mg-1.0Bi-1.0Mn-1.0Al-0.5Ca-0.3Zn (BMAXZ11110, wt%) alloy, subjected to extrusion at low temperature of 300 °C and high ram extrusion speed of 9 mm/s, have been systematically investigated. This alloy exhibits excellent microstructural thermo-stability during high-speed extrusion without obvious grain coarsening, especially for the edge of alloy bar. Profuse micro/nano-scale second phases (Mg2Bi2Ca, Al8Mn5 and α-Mn) and the co-segregation of Ca and Zn atoms at grain boundaries (GBs) /residual dislocations can be observed. The co-effects of nano-scale phases and solute segregation facilitate the formation of bimodal grain structure in the BMAXZ11110 alloy. At RT, it possesses high tensile yield strength (TYS, ∼ 327.1 MPa), and GB strengthening is the most primary mechanism. At 250 °C, this alloy still can maintain relatively high TYS (∼ 187.8 MPa), indicating that it also exhibits high heat resistance. Even though the contribution of GB strengthening on the TYS decreases at 250 °C, solute segregation strengthening increment makes up for its reduction to a large extent. Hence, this study will be helpful for developing a new generation of high-strength high-speed extruded Mg-Bi base alloys accompanied with good heat resistance.

Enhanced in-vitro biodegradation, bioactivity, and mechanical properties of Mg-based biocomposite via addition of calcium-silicate-based bioceramic through friction stir processing as resorbable temporary bone implant

Bioabsorbable Mg and alloys have been used as metallic biomaterials for orthopedic implant applications due to their similar mechanical properties to human natural bone. High biodegradation rate is the main reason for limiting clinical applications of Mg and alloys in biological media. In order to achieve long-lasting bio applications of bioabsorbable WE43 Mg alloy, it is necessary to improve strength and bioactivity and control biodegradation rate of this material. In this study, Mg-based biocomposites are produced using friction stir processing (FSP) by addition of wollastonite (CaSiO3) calcium-silicate-based bioactive reinforcing particle into Mg matrix. The results showed that applied severe plastic deformation during FSP caused formation of ultra-fine grain structure with homogenous distribution of secondary phase particles, which resulted in a remarkable improvement of ductility, strength and load bearing capacity of FSPed Mg matrix. Also, biodegradation behavior of resulting biocomposite was evaluated using electrochemical methods and in-vitro immersion test in simulated body fluid (SBF) and phosphate-buffered saline (PBS) at 37.5 °C. The results revealed that processed bioabsorbable Mg alloy showed a lower biodegradation rate compared to monolithic Mg alloy. Furthermore, the presence of wollastonite bioceramic particles significantly enhanced strength and reduced biodegradation of the Mg-based biocomposite. Moreover, the addition of wollastonite bioceramic particles positively affected the bioactivity of Mg matrix by forming a cauliflower shaped bone-like hydroxyapatite layer on the surface after 28 days of immersion in SBF and stimulate bone tissue regeneration.

Microstructure, mechanical characteristics, and electrochemical behavior of the wide-area stir zone fabricated in Al5083 by friction stir processing with overlapping technique

In the current study, a wide-area stir region was created in Al5083 aluminum alloy using multi-pass friction stir processing (FSP) with 50% pin overlapping. Microstructural investigations such as grain structure analysis and intermetallic particle (IMPs) distribution were carried out on processed alloys using optical and scanning electron microscopy (SEM). Recrystallized fine grains were developed after FSP due to the intense plastic straining and dynamic recrystallization. It was also identified that the grain refinement was uniform in the stir region of all overlapping passes, resulting in uniform hardness over the wide-area stir region. Three different types of IMPs, such as needle shape iron-based IMPs, round shape magnesium-based IMPs, and the very fine magnesium-based IMPs along the grain boundaries, were identified from the SEM analysis. The tensile test findings showed that the elongation improved drastically after overlapping FSP, while the hardness and tensile strength were found to be decreased due to high temperature thermal cycles. Electrochemical investigations revealed that the corrosion rate decreased after FSP due to the formation of uniform grain structure and dissolution of iron-based IMPs.

On the Mechanism of Formation of Bimodal Grain Structure in Al–4.5Mg–0.7Sc–0.3Zr Alloy Processed by Laser Powder Bed Fusion

Scalmalloy is an Al–Mg alloy with additions of Sc and Zr originally developed as a high‐strength aluminum alloy with σ0.2 ≥ 450 MPa for aerospace industry. It is now well understood that the alloy is amendable for processing by laser powder bed fusion (LPBF). However, the mechanism of formation of the equiaxed‐columnar bimodal grain structure during LPBF is not ascertained yet, fully. Herein, this gap is addressed with special focus on the distributions of critical elements such as Sc and various particles that form during LBPF. It is found that strong and weak segregation of Mg and Sc, respectively, occurs in the final solidification areas of the fine‐ and equiaxed‐grain regions. The coarser and columnar grain regions show weak segregation of Mg and no Sc segregation. A priori knowledge on the Al–Sc eutectic reaction, its dependence on cooling rates, and the well‐known thermal and solidification conditions related to the track location during LPBF is used to ascertain the mechanism of formation of the bimodal grain structure. The mechanism suggested is substantiated by the location‐dependent elemental distributions and the various particles that are observed.

Increasing the Thermal Stability and High-Temperature Strength of Vanadium Alloys by Strengthening with Nanosized Non-Metallic Particles

Using the methods of scanning and transmission electron microscopy, the features of the structural-phase state of a vanadium alloy of the V-Cr-Ta-Zr system after a combined treatment, which consisted in cyclic alternation of thermomechanical and chemical-heat treatments, were studied. The values of yield strength and ductility of the V-Cr-Ta-Zr alloy were determined, depending on the stabilization and test temperatures. It was established that, after the combined treatment, the structural-phase state of the V-Cr-Ta-Zr alloy was composite, in which the joint implementation of dispersion and substructural strengthening ensured the formation of a gradient grain structure with a polygonal state, the elements of which were fixed by nanosized ZrO2 particles characterized by a high thermal stability. Such modification of the microstructure was accompanied by an increase in the high-temperature strength and a shift in the upper limit of the temperature stability interval towards high temperatures, of up to 900 °C. It was assumed that the polygonal state inside the grains contributed to the implementation of cooperative mechanisms of the dislocation-disclination type, which ensured the accommodation of the material in the "high-strength state" under loading.

The effect of the TiC-TiB2 nanoparticles on the microstructure and mechanical properties of Al-Mn-Si strips fabricated by twin-roll casting

In this work, Al-Mn-Si and TiC-TiB2/Al-Mn-Si strips were prepared by vertical-type twin-roll casting (TRC), and the effect of TiC-TiB2 nanoparticles (NPs) on the microstructure and mechanical properties of TRC Al-Mn-Si strips were studied. The TRC strips had the characteristics of coarse grains near the surface and fine grains in the center. The introduction of NPs resulted in the formation of uniform and fine grain structures due to the grain refinement effect of NPs. The refining effect on the surface grains was much greater than that on the central grains because the larger thermal undercooling of the melt at the surface led to the improvement of the nucleation efficiency of NPs. TiC-TiB2 particles could eliminate the central segregation of TRC Al-Mn-Si strips due to the control of solute diffusion by the uniform and fine grain structures, thereby reducing α-Al(Mn, Fe)Si formation in the central region. The mechanical properties of the TRC Al-Mn-Si strips were improved with the introduction of NPs. The yield strength at room temperature was increased from 79.0 MPa to 92.9 MPa, and the uniform elongation was increased from 7.2% to 10.1%, due to the fewer eutectic α-Al(Mn, Fe)Si, refined precipitates and grain structures caused by the addition of the TiC-TiB2 particles.