Microstructure Of Solid Solution Research Articles

Room Temperature Electrochemical-Shock Synthesis of Solid-Solution Medium-Entropy Alloy Nanoparticles for Hydrogen Evolution.

For millennia, humankind has discovered great benefits in alloying materials. Over the past 100 years, a renaissance in nanoscience has cemented the importance of nanoparticles in a variety of fields ranging from energy storage and conversion to cell biology. While many synthetic strategies exist for nanoparticle and alloy nanoparticle formation, new methods are necessary to create nanoparticles under unprecedented conditions. Here, we demonstrate a simple technique to electrodeposit solid-solution alloy nanoparticles at room temperature. When metal salts of platinum, gold, and palladium are confined to nanodroplets suspended in oil, and then a nanodroplet collides with a sufficiently negative-biased electrode to reduce the metal salts at the mass-transfer limitation, solid-solution alloy nanoparticles form. High-angle annular dark-field scanning transmission electron microscopy and single atom energy dispersive X-ray spectroscopy confirm the solid-solution microstructure of the nanoparticles. The results also confirm the nanodroplet's ability to tune alloy microstructures from amorphous to solid-solution. We further extend our technique by adding salts of silver, which lead to the synthesis of polycrystalline medium-entropy alloys. Finally, we go on to show the application of our midentropy alloys toward renewable and clean energy devices by highlighting their electrocatalytic activity toward hydrogen evolution reaction. Our method is unrivaled in its simplicity and will find applications across various fields of study.

Features of the crystal, magnetic and micro-structure of solid solutions of the (1-x)Pb(Fe1/2Nb1/2)O3—xPb(Fe2/3W1/3)O3 system

The results of the crystal structure studies by method X-ray diffraction and Mössbauer effect and the microstructure analysis by high resolution transmission electron microscopy of solid solutions of the (1-x)PbFe1/2Nb1/2O3-xPbFe2/3W1/3O3 system are presented. X-ray diffraction and transmission electron microscopy studies at room temperature reveal the presence of extended planar defects - crystallographic shift planes in the crystal structure of the solid solutions (1-x)Pb(Fe1/2Nb1/2)O3-xPb(Fe2/3W1/3)O3 system. The structure of the solid solutions (1-x)Pb(Fe1/2Nb1/2)O3-xPb(Fe2/3W1/3)O3 system is demonstrated to comprise regions of disparate chemical composition, as evidenced by a range of techniques.

Phase Composition of AlTiNbMoV, AlTiNbTaZr and AlTiNbMoCr Refractory Complex Concentrated Alloys: A Correlation of Predictions and Experiment

Designing complex concentrated alloys (CCA), also known as high entropy alloys (HEA), requires reliable and accessible thermodynamic predictions due to vast space of possible compositions. Numerous semiempirical parameters have been developed for phase predictions over the years. However, in this paper we show that none of these parameters is a robust indicator of phase content in various refractory CCA. CALPHAD proved to be a more powerful tool for phase predictions, however, the predictions face several limitations. AlTiNbMoV, AlTiNbTaZr and AlTiNbMoCr alloys were prepared using blended elemental powder metallurgy. Their phase and chemical composition were investigated by the means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Apart from the minor contamination phases (Al2O3 and Ti(C,N,O)), AlTiNbMoV and AlTiNbMoCr exhibited single-phase solid solution microstructure at the homogenization temperature of 1400 °C, while Al3Zr5 based intermetallics were present in the AlTiNbTaZr alloy. None of the simple semiempirical parameter was able to predict phase content correctly in all three alloys. Predictions by CALPHAD (TCHEA4 database) were able to predict the phases with limited accuracy only. Critical limitation of the TCHEA4 database is that only binary and ternary phase diagrams are assessed and some more complex phases cannot be predicted.

Structure and electrical properties of (1-x)Bi3TiTaO9-xNa0.5Bi2.5Nb2O9 piezoelectric ceramic

The lead-free piezoelectric ceramics (1-x)Bi3TiTaO9–xNa0.5Bi2.5Nb2O9 [(1-x)BTT–xNBN; x = 0.0; 0.2; 0.5; 0.7; 1.0] were prepared using the traditional solid-state method, and the microstructure and electrical properties of the novel solid solution (1-x)BTT–xNBN were studied. XRD data and Raman spectroscopy analysis indicated that Na ions and Nb ions had been incorporated into the designed lattice, forming a stable solid solution. The piezoelectric performance of the (1-x)BTT–xNBN ceramics was improved for two reasons: on one hand, the incorporation of NBN could suppress the leakage current caused by Ti ions, effectively reducing the contribution of oxygen vacancies to the direct current resistivity, thereby increasing the ceramic's direct current resistivity (ρdc); on the other hand, the orthorhombic distortion was reduced, and the remanent polarization was enhanced. Among them, the 0.3Bi3TiTaO9-0.7Na0.5Bi2.5Nb2O9 ceramic demonstrated excellent comprehensive performance: the values of d33, Tc, and Pr were 14.4 pC/N, 777.8 °C, and 9.82 μC/cm2, respectively. Specifically, at 500 °C, tanδ and ρdc were 0.67 % and 1.01 × 108 Ω∙cm, respectively, and after depolarization at 750 °C, its d33 remained at 97.92 % of the original value.

Strengthening a non-equiatomic quaternary high-entropy alloy via concurrent gradient structures of nanotwin and dislocation cell

One main drawback of FCC high-entropy alloys (HEAs) is their insufficient room temperature yield strength. In this work, concurrent gradient structures of nanotwins and dislocation cells have been introduced into a non-equiatomic quaternary Fe40Ni20Co20Cr20 (at. %) high-entropy alloy by ultrasonic shot peening to meet this challenge. The gradient alloy exhibits a significantly enhanced yield strength, i.e., from the original 204 MPa to 559 MPa, combining with a well-retained ductility of 29 % and a good work hardening ability. Strengthening mechanisms at different depths (5, 30, 200, 400 μm) are also carefully discussed. The current work presents a strategy for hardening FCC HEAs significantly while maintaining the single solid solution microstructure.

Enhanced Strength–Ductility Synergy of Mg–6Zn Alloy Wire by Inducing Guinier–Preston Zone Precipitation

This article designs a strategy of introducing ultrafine precipitates into single‐phase microstructure to enhance Mg–6Zn alloy wire. Three combined processes including equal channel angular pressing (ECAP), direct extrusion, and multipass drawing are used to produce 0.3 mm‐diameter wire. The results show that an isothermal process of ECAP, extrusion, and drawing at 32 °C (named route B) produces a near‐fully solid solution microstructure and causes a very high elongation of 21% as well as an ultimate tensile strength of 24 MPa. Furthermore, on this basis, the addition of an aging treatment before drawing induces the precipitation of the Guinier–Preston zone in the near‐single‐phase Mg matrix and improves the tensile elongation to 28%, and the ultimate tensile strength also is increased to 290 MPa.

Effect of Annealing Temperature on Microstructure and Properties of Solid Solution Extruded Mg–2.0Zn–1.0Y–0.5Zr Alloys

In this investigation, the effects of different annealing temperatures (180, 200, 220, 240, 260, and 280 °C) on the microstructure evolution and properties of an extruded Mg–2.0Zn–1.0Y–0.5Zr (wt%) magnesium alloys were determined. Optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion, electrochemical corrosion experiments, and tensile testing were performed. Research has found that combining hot extrusion with subsequent low-temperature annealing significantly improves the strength, plasticity, and corrosion resistance of alloys due to grain refinement and a reduced dislocation density. The alloy was completely recrystallized at an annealing temperature of 240 °C for 4 h after solid solution extrusion, and the grains were fine and uniform, demonstrating the best comprehensive properties. Its corrosion rate, ultimate tensile strength, yield strength, and elongation were 0.454 ± 0.023 mm/y, 346.7 ± 8.9 MPa, 292.4 ± 6.9 MPa, and 19.0 ± 0.4%, respectively. The corrosion mechanism of the specimens under extruded and annealed conditions was analyzed. After annealing at 240 °C for 4 h, the dislocation and bimodal grain structure of the samples were almost eliminated, resulting in uniform and fine grains, which were conducive to the formation of a more uniform and denser oxide film, thus improving the corrosion resistance of the alloy.

The role of the preparation route on microstructure and mechanical properties of AlCoCrFeNi high entropy alloy

Nearly equiatomic AlCoCrFeNi alloy samples were prepared by induction melting and mechanical alloying (MA) combined with spark plasma sintering (SPS). The cast sample showed a dendritic microstructure composed of spinodally decomposed nanometric constituents of the B2 and BCC phases. The spark plasma sintered sample exhibited an ultrafine-grained microstructure of B2 phase and FCC solid solution and Cr23C6 carbides. The MA + SPS sample was strengthened by compressive stress-strain test up to a yield strength of 2029 ± 5 MPa, resulting significantly higher compared to 1366 ± 32 MPa of the cast sample. In addition to the higher compressive yield strength, the sintered sample exhibited a hardness of more than 130 HV higher compared to the cast alloy. On the other hand, the cast alloy showed high plastic deformation (29%) and significantly high ultimate compressive strength of 3072 ± 122 MPa. Together with these mechanical characteristics, the MA + SPS sample showed good thermal stability while preserving the mechanical properties even after annealing at 800 °C. This was not the case with the cast sample, in which ductility and ultimate strength significantly decreased upon annealing at 800 °C. A substantial yield strength reduction of both MA + SPS and cast samples was recorded when tested at 800 °C. Nevertheless, stress-strain curve trends were observed to be quite different between the two samples, thus suggesting dissimilar deformation mechanisms under high-temperature compression.

The dynamic recrystallization microstructure characteristics and the effects on static recrystallization and mechanical properties of Al–Mg–Si alloy

It is essential to clarify the dynamic recrystallization microstructure characteristics of age-hardened aluminum alloys and the effects on the static recrystallization microstructure and aging mechanical properties, with the aim of selecting the deformation conditions reasonably. This work investigated the evolution of the hot deformation and solid solution microstructures and aging mechanical properties of Al–Mg–Si alloy with deformation temperatures of 400–550 °C, strain rates of 0.01–10 s−1, and true strains of 0.2–0.8. Research has shown that it is advantageous for the DDRX and CDRX mechanisms to annihilate and rearrange dislocations simultaneously for forming deformation microstructure with uniform grain size at higher deformation temperatures and lower strain rates (such as 500 °C, 0.01 s−1). Additionally, the lower dislocation density in deformation microstructure facilitated the inhibition of static recrystallization during subsequent solid solution treatment, whereas lower deformation temperature and higher strain rate conditions should result in a greater degree of static recrystallization and reduce the uniformity of the solid solution microstructure. Hardness test results demonstrated that the deformation temperature of 480–520 °C and strain rate of 0.03–0.2 s−1 were the appropriate conditions for Al–Mg–Si alloy to attain finer and uniform grains and superior properties after solid solution treatment. The extruded samples within the above conditions (500 °C, 0.032 s−1) exhibited higher UTS and YS after solid solution and aging treatment, reaching 444 ± 2 MPa and 426 ± 4 MPa, respectively.

Effect of annealing time on solid solution microstructure and memory properties of additive Fe-Mn-Si-Cr-Ni alloy

Annealing plays a pivotal role in optimizing the morphology and quantity of cooling martensite within the solid solution matrix of additively manufactured Fe-based memory alloys. In this study, we utilized laser filament deposition to create Fe-17Mn-6Si-9Cr-5Ni alloy, and subsequently compared the microstructure and memory properties of the alloy following two treatments: a 900[Formula: see text]C× 60 min solution treatment and a solid solution + annealing treatment at various durations at 600[Formula: see text]C. Our aim was to investigate how annealing time impacts the memory properties of additively manufactured Fe-Mn-Si-Cr-Ni alloys in their solid solution state, focusing on microstructural changes during the metamorphic and revertive states. The findings reveal that after the solution treatment, the alloy contains a higher number of cooling martensite units, but their arrangement is disordered, indicating a lower degree of order. However, after a 10 min annealing treatment, the quantity of cooling martensite slightly diminishes, while their arrangement becomes more orderly. With prolonged annealing, both the quantity of cooling martensite and the grain size of the alloy decrease significantly. Consequently, after a 10-min annealing treatment, the alloy exhibits a 31% increase in shape recovery rate under a 6% pre-deformation compared to the alloy subjected solely to the solution treatment, and the recoverable strain reaches 4.59%. This demonstrates that an appropriately timed annealing process can transform the disordered cooling martensite within the solid solution structure of additive manufacturing Fe-based memory alloys into a more regular arrangement, thereby enhancing their memory performance.

Excellent sintering resistance of zirconia-based bi-phase solid solution ceramic coating

The microstructure and sintering behavior of zirconia-based bi-phase solid solution (BPS) ceramic coating prepared by air plasma spraying have been investigated. It is found that the BPS coating is composed of cubic and tetragonal phases, which are well-adhered. During the 1200 °C thermal cycling, the densification of intersplat pores and cracks is inhibited due to the differential sintering of nano-grains and the high density of oxygen ions located in the crystal plane. The average grain diameter and Young’s modulus are reduced, and the thermal conductivity is maintained at a constant level after 250 thermal cycles. The sintering resistance of BPS coating is 40 % higher than 8YSZ coating.

Thermal stability of laser track microstructures in an Al-Cr-Co-Mn-Zr I-phase alloy

Laser glazing of solid metal surfaces is an efficient and cost-effective way to evaluate the potential of an alloy system for use in metal additive manufacturing (MAM), but there are concerns about the stability of the resulting microstructures. Here it is shown that in situ transmission electron microscopy heating experiments on specimens cut from laser glazing tracks using focused ion beam methods can provide a useful insight into the transformation phenomena that occur upon reheating. Examples of such experiments are presented for laser tracks in a powder-processed Al-Cr-Mn-Co-Zr alloy, which contains a complex distribution of icosahedral quasicrystal (I-phase) dispersoids in a polycrystalline FCC Al matrix. Initial ramped heating experiments were performed to identify suitable conditions for isothermal studies of transformation pathways. Tracks with the lowest laser energy input exhibited supersaturated solid solution microstructures. These were stable during ramped heating to around 375 °C. For isothermal exposures at 400 °C there was precipitation of Al4(Cr,Mn) both at grain boundaries and within the FCC Al matrix phase. In tracks with higher laser energy input, equiaxed I-phase dispersoids were formed in the matrix. These microstructures were stable during ramped heating to around 400 °C. In isothermal experiments at 425 °C, there was precipitation of Al4(Cr,Mn), followed by the onset of I-phase decomposition. The partially decomposed dispersoids exhibited an I-phase core surrounded by a shell of Al45(Cr,Mn)7. In isothermal experiments at 450 °C, the dispersoids decomposed completely to form Al4(Cr,Mn), indicating that Al45(Cr,Mn)7 is a metastable intermediate transformation product. These observations provide a useful guide to the transformations that might occur during MAM processing of this alloy system.

High entropy nanomaterials for energy storage and catalysis applications

In the past decade, high entropy alloys have been a research field of interest largely attributed to the enormous possibilities in alloy compositions, solid solution microstructures, and enhanced properties. The progress accomplished so far in the innovative growth and development of the mechanical, nanomechanical, chemical, electrochemical properties for energy storage systems using high entropy alloys on the nanoscale has limited reports in the literature. Mastering the synthesis of high entropy alloys is the deciding factor, if not the holy grail, when interested in a new material. For nanoparticles, in particular, this is true. Hence, the study on the production of high entropy alloy nanoparticles (HE-NPs) and the impact of synthesis on the structure of the resulting nanomaterial is valid for newly emerging components like HEA-NPs and the linkages between synthesis, structure, and property are essential for creating HEA-NP-based applications for energy storage applications, requiring the creation of a fundamental protocol to enable their mass manufacture and efficiency in service. In this study, we have presented a straightforward review of high entropy alloys, recent advances in high entropy nanoparticles and their various syntheses for energy and catalysis applications.

Sintering behavior and microstructure of (1-x)MgAl2O4-xMg2TiO4 spinel solid solutions prepared by isostructural heterogeneous nucleation

Magnesium aluminate (MgAl2O4) spinel has grasped considerable attention in high-temperature application by right of its excellent properties. However, the poor sintering behavior of MgAl2O4 is detrimental to its further development. In the present work, the application of isostructural heterogeneous nucleation method provides a novel idea for optimizing the sintering behavior of refractory materials. A series of (1-x)MgAl2O4-xMg2TiO4 (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) spinel solid solutions with a present ration of components were fabricated from light calcined magnesia, reactive alumina and pre-preparation Mg2TiO4. The effect of Mg2TiO4 heterogeneous nucleating agent on the crystalline phase, densification, and microstructure evolution of MgAl2O4–Mg2TiO4 spinel solid solutions was studied. The XRD, XPS, and EDS results showed that Mg2TiO4 entered the lattice of MgAl2O4 to form a spinel solid solution, and the heterovalent substitution process was identified, where Ti4+ and Mg2+ ions of larger radius in the Mg2TiO4 replaced the Al3+ of smaller radius in the MgAl2O4. For the sample at x = 0.08, the spinel solid solutions exhibited the optimized densification with a relative density of 93.3%, an apparent porosity of 1.2%, and a compressive strength of 84.5 MPa. A significant increase in densification was related to the lattice distortion induced by ion size mismatch during the heterovalent substitution, thus accelerating the diffusion rate of Mg2+ and Al3+ ions in the spinelisation state. Moreover, the solid solubility content of Ti4+ in the MgAl2O4–Mg2TiO4 spinel solid solutions had a significant effect on the grain morphologies. The Mg2TiO4 heterogeneous nucleating agent significantly increased the spinelisation rate of MgAl2O4 spinel with negligible effect on densification.

Combined effects of heat treatment and TiB2 content on the high-temperature tensile performance of TiB2-modified Ni-based GH3230 alloy processed by laser powder bed fusion

Laser powder bed fusion (LPBF) is widely used to manufacture advanced nickel-based superalloys for aero-engine components. LPBF-formed GH3230 nickel-based superalloy, however, suffers cracking and high residual stresses. This study systematically investigated the effects of different contents of submicron TiB2 particles on crack suppression and post-heat treatment for residual stress relief and improved microstructure anisotropy. The introduction of both 0.5 wt% and 1 wt% TiB2 achieved complete crack suppression in the LPBF-manufactured GH3230 specimens. As-built specimens with 0.5 wt% and 1 wt% TiB2 exhibited a supersaturated solid-solution microstructure, with the solid elements (Cr, Mo and W) almost fully dissolved in the matrix and only a limited number of Mo and Cr enriched carbides precipitated at the grain boundaries. Electron backscattered diffraction (EBSD) characterization demonstrated that a large number of deformed grains remained in the as-built specimens. After heat treatment, the residual stresses were released and the number of deformed grains significantly reduced. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization demonstrated the disappearance of the dense dislocation network in the as-built specimens after heat treatment, accompanied by the precipitation of a large number of W-rich M6C carbides. This paper also discusses elevated-temperature (900 °C) mechanical properties. The ultimate tensile strength (UTS) values of the as-built GH3230 with 0.5 wt% (GH-0.5) and 1 wt% TiB2 (GH-1) specimens were 255 and 290 MPa, respectively. Compared to the as-built materials, the UTS values decreased by 40 and 53.5 MPa, respectively, after heat treatment. The paper also discusses the effect weight of the second-phase, solid-solution and dislocation-strengthening mechanisms on the elevated-temperature mechanical properties. The findings indicate that the added 1 wt% TiB2 particles and the solid-solution elements contributed about 106.2 MPa and 111.5 MPa stress, respectively, in the heat-treated GH-1 specimen. The precipitated M6C carbides after heat treatment, however, were not found to significantly improve the high temperature strength. This work is expected to provide a reference for industrial applications to improve the LPBF formability of nickel-based superalloys and to acquire attractive microstructures.

Composition design to tune the mechanical behavior of a TRIP-TWIP (CrMnFeCoNi)50 Fe50-xCrx multi-principal element alloys

The utilization of the laser melting deposition (LMD) method to synthesize the (CrMnFeCoNi)50Fe50-xCrx (x = 5, 10, and 15 at.%) multi-principal elements alloys (MPEAs) are successfully demonstrated. It discovers that all (CrMnFeCoNi)50Fe45Cr5, (CrMnFeCoNi)50Fe40Cr10, and (CrMnFeCoNi)50Fe35Cr15 MPEAs retain a single-phase solid solution microstructure, and the in-situ structure transformation found in the matrix is ascribed to the reduction of the stability of FCC structure via appropriately tailoring constituent elements. (CrMnFeCoNi)50Fe45Cr5 MPEA exhibits the simultaneous enhancement in the plasticity (almost 100%) and the tensile strength (from 415 MPa to 470 MPa) resulting from the co-contribution of deformation-induced twining and tiny amounts of precipitation for M23C6 carbide at ambient temperature. Inversely, (CrMnFeCoNi)50Fe35Cr15 displays remarkable improvement in the tensile strength (∼ 600 MPa) at the sacrificing of the plasticity elongation (from 50% to 32%) originating from the contribution of strain-induced structure transformation. Here, the transformation-induced twinning and transformation-induced ductility are successfully achieved by tuning the stability of the constituent phases in the (CrMnFeCoNi)50Fe50-xCrx MPEAs. These discoveries not only distinctly distinguish the tensile strength and plasticity of the (CrMnFeCoNi)50Fe50-xCrx MPEAs from the corresponding CoCrFeMnNi MPEA, but also pave the way for designing and enhancing the comprehensive properties of MPEAs and other structural materials for engineering applications.

Optimized mechanical properties of titanium-oxygen alloys by powder metallurgy

Oxygen solid solution-strengthened titanium-oxygen (Ti–O) alloys with ultrahigh yield strength and large ductility were designed and synthesized via high-energy ball milling (BM) combined with spark plasma sintering (SPS) in compression. The morphology, dispersion state, and solid solution microstructure of the Ti–O alloys were optimized by regulating the mixing method, sintering temperature, and added oxygen content. Outstanding properties that include a compressive yield strength of 1220 MPa and large ductility of 36.3% were achieved after 1 h high-energy BM and 1000 °C SPS with the addition of about 1.8 at% oxygen. The grain refinement and oxygen solid solution strengthening indicate that the dense morphology, refined grain size, and oxygen solid solute atoms are responsible for the balance between the superior strength and ductility of the titanium alloys.

Phase stability and magnetic and electronic properties of a spark plasma sintered CoFe – P soft magnetic alloy

More efficient power conversion devices are able to transmit greater electrical power across larger distances to satisfy growing global electrical needs. A critical requirement to achieve more efficient power conversion are the soft magnetic materials used as core materials in transformers, inductors, and motors. To that effect it is well known that the use of non-equilibrium microstructures, which are, for example, nanocrystalline or consist of single phase solid solutions, can yield high saturation magnetic polarization and high electrical resistivity necessary for more efficient soft magnetic materials. In this work, we synthesized CoFe – P soft magnetic alloys containing nanocrystalline, single phase solid solution microstructures and studied the effect of a secondary intermetallic phase on the saturation magnetic polarization and electrical resistivity of the consolidated alloy. Single phase solid solution CoFe – P alloys were prepared through mechanically alloying metal powders and phase decomposition was observed after subsequent consolidation via spark plasma sintering (SPS) at various temperatures. The secondary intermetallic phase was identified as the orthorhombic (CoxFe1−x)2P phase and the magnetic properties of the (CoxFe1−x)2P intermetallic phase were found to be detrimental to the soft magnetic properties of the targeted CoFe – P alloy.

Classifying and benchmarking high-entropy alloys and associated materials for electrocatalysis: A brief review of best practices

In light of the immense compositional diversity of high-entropy materials (HEMs) recently reported ( e.g. , high-entropy chalcogenides, perovskites, ceramics, etc.) and the relatively amorphous definition of High-Entropy, it is imperative that consistent material classification and benchmarking practices be employed to facilitate comparison between reported figures of merit. In this opinion, an updated form of the numerical high-entropy definition is reviewed, which renders a universal entropy metric applicable to high-entropy alloys and emerging HEMs alike. Analytical methods to verify the existence of a solid-solution microstructure, elucidate atomic valence states, and probe atomic disorder are discussed with literature examples to facilitate the physical classification of HEMs. Electrocatalytic benchmarking is discussed in the context of water-splitting reactions and best practices are reviewed for determining the electrocatalytically active surface area, reaction overpotential, and electrocatalyst stability.

Formation mechanism of AlN-SiC solid solution with multiple morphologies in Al-Si-SiC composites under flowing nitrogen at 1300 °C

The non-oxide-reinforced phase AlN-SiC solid solution with high performance was successfully synthesized in the resin-bonded Al-Si-SiC composites under flowing nitrogen at 1300 °C. The AlN-SiC solid solution was synthesized by three paths of liquid-solid, gas-solid and gas-gas reactions through modulation of Al/Si ratio, and controllable microstructure of AlN-SiC solid solution was attained. The phase composition and microstructure of the sintered samples were characterized by XRD and SEM, combined with thermodynamics, the formation mechanism of AlN-SiC solid solution was investigated and the reaction model was established. Al was not detected while Si was detested by XRD. Granular, short columnar and whisker-like AlN-SiC solid solution were generated and their positions varied. As the temperature increases, the partial pressure of oxygen decreases due to the oxidation of Al, Si and SiC on the surface of the sample, inside the sample, the active oxidation takes place, generating Al2O(g), SiO(g) and CO(g). Due to the low oxygen partial pressure, Al is preferentially nitrided to form a thin AlN layer on its surface. The AlN layer is broken as the temperature increases, then liquid Al with carbon from resin begins to flow, leaving the residual shell of AlN in situ. When it flows to the surface of Si, Al-Sialloy is formed locally inside the Si particles under the wetting effect of C, then hexagonal AlN-SiC solid solution is formed inside the Si shell. Part of SiO(g) + CO(g) diffuses into the interior of the AlN residual shell and reacts by aggregation to form a granular AlN-SiC solid solution in the shell wall; others diffuses into the pores of the sample for vapor deposition, and finally forms stacked hexagonal flaky whiskers. The in-situ generated of AlN-SiC solid solution with multiple morphologies in the composite plays a joint toughening effect, which can significantly enhance the comprehensive performance of the composite. In this experiment, the synthesis of AlN-SiC solid solution without sintering aids under normal pressure at a low temperature. It is expected to be applied to the blast furnace and to realize the longevity of blast furnace.