Improvement In Yield Strength Research Articles

Microstructure and mechanical properties of MoNbVTa0.5Alx refractory high entropy alloys

The specific strength of refractory high entropy alloys (RHEAs) is usually impaired due to the high density of constituent elements. In order to develop a low-density RHEA, the microstructure and mechanical property of MoNbVTa0.5-based RHEAs with various Al additions have been investigated in this study. All samples exhibited a monolithic BCC solid solution structure. The addition of Al resulted in improved yield strength but a degraded plasticity at ambient temperature. In contrast, the yield strength consistently decreased with increasing Al content at elevated temperatures, and the softening occurred at ~1000 °C. MoNbVTa0.5Al0.3 exhibited high specific strengths of 119.2 MPa cm3/g, 108.6 MPa cm3/g and 97.3 MPa cm3/g at 600 °C, 800 °C, and 1000 °C, respectively.

Experimental study on the heat input behavior of wire-arc additively manufactured 316L stainless steel parts for repairing applications

Wire arc additive manufacturing (WAAM) as an emerging manufacturing technique for fabricating large size metallic components with a higher deposition rate and lower material wastage. In this research, a thin walled-part was fabricated from stainless steel 316L with various heat input (HI) (low heat deposited wall (LHDW) and high heat deposited wall (HHDW) using the cold metal transfer (CMT)-based WAAM process. The microstructure characteristics, metallurgical characterization, and mechanical properties of the WAAM manufactured thin-walled component were examined. The deposited wall measuring 120 mm in length and 50 mm in height was fabricated by WAAM using ER316L wire and CMT. Microstructure of the deposit parts consists of the equiaxed, coarse, and columnar grains with epitaxial growth of dendrites were formed. The decrease in HI leads to the improvement of material hardness, yield and ultimate tensile strength (UTS) as well as the percentage elongation after fracture of the material decreases. EBSD analysis demonstrates the average grain size of 0.98 µm in LHDW and 2.43 in HHDW respectively. XRD results shows that main crystal structure found in WAAM thin-walled sample was γ-austenite phases. The microhardness distribution of the fabricated component exhibited the stability characteristics with the average value ranging between 213–237 HV. The tensile studies demonstrate the UTS of the LHDW and HHDW along the horizontal direction are 477 MPa greater than the vertical direction of 468 MPa and observed the anisotropy properties. The fractured surface was characterized by the emergence of obvious dimples revealing the ductile fracture. The lower HI and finer solidification structure of component fabricated by LHDW has greater tensile and hardness properties than that of HHDW. This study presents the initial assessment results for repairing stainless steel components subjected to mechanical damage.

Microstructure development and strengthening behaviour in hot-extruded Ti-Mo alloys with exceptional strength-ductility balance

A series of strong and ductile Ti-Mo alloys containing 2.5, 5, 7.5 and 10 wt% Mo was experimentally investigated by a two-stage blended-elemental powder metallurgy process. This process consisted of a spark plasma sintering stage for powder-consolidation and in-situ-homogenisation, and a hot extrusion stage for densification and microstructure enhancement. Microstructures in the extruded alloys changed from α dominant to β dominant with molybdenum addition. Simultaneously, a grain refinement effect was observed due to suppressed α precipitation and increase β retention. A significant strengthening effect was observed with molybdenum addition. In comparison with similarly processed commercially pure titanium, Ti-10Mo exhibited a yield strength improvement of 290 % to 1382.8 MPa, and an ultimate tensile strength improvement of 239 % to 1496.5 MPa. Meanwhile, Ti-5Mo exhibited a yield strength improvement of 211 % (1007.9 MPa) without any substantial reduction in ductility, resulting in an exceptional tensile toughness of 361.3 MJ.m−3. A quantitative analysis of strengthening mechanisms reveals considerable strengthening effects from solid solution strengthening, dislocation strengthening, and grain refinement effects. These factors arise from the novel multi-modal microstructures formed by thermomechanical processing at super-transus temperatures. The newly achieved balance of strength and ductility appears to be unrivalled amongst all previously reported binary Ti-Mo alloys.

Microstructures and mechanical behaviors of a directional lamellar Ti-48Al-2Cr-2Nb alloy produced by laser additive manufacturing

Extremely large thermal gradient is considered as a unique characteristic of additive manufacturing, which can be utilized to fabricate directionally solidified alloys. In this study, we successfully fabricated a bulk Ti-48Al-2Cr-2Nb alloy with directional solidified features by the approach of direct laser deposition. The microstructural characterizations revealed that our additively manufactured (AMed) alloy was dominantly featured by a directional α2/γ lamellar microstructure. Moreover, there occurs an intriguing phenomenon that the orientation relationship between α2 and γ lamellae appears a slight deviation from the well-known Blackburn relationship, which was seldom observed in previous reports. Additionally, some amounts of βo and C14-type laves phases also formed and dispersed in the lamellar microstructure. Mechanical investigations indicate that the AMed alloy achieved an improvement in yield strength at room temperature. Moreover, its yield strength can remain 630 MPa at 800 °C, comparable to the value at room temperature, and only a slight decrease occurred when the temperature was increased to 900 °C, which is superior to that of the cast one. Then, the related strengthening mechanisms were discussed based on the directional lamellar features and the particularity in orientation relationship.

300 MPa grade high-strength ductile biodegradable Zn-2Cu-xMg (x = 0.08, 0.15, 0.5, 1) alloys: The role of Mg in bimodal grain formation

300 MPa grade biodegradable Zn-2Cu-xMg (0.08, 0.15, 0.5, and 1 wt.%) alloys with different bimodal grain structures were obtained by casting and hot extrusion. The effects of the Mg element on the microstructure, mechanical properties, and dynamic recrystallization (DRX) behavior of the as-extruded Zn-2Cu-xMg alloys were investigated. The obtained results showed that CuZn4 butterfly particles and eutectic net structure (η-Zn + Mg2Zn11) are formed in the as-cast Zn-2Cu-xMg alloys. The as-extruded Zn-2Cu-0.08Mg and Zn-2Cu-0.15Mg alloys exhibited finer DRXed and coarser unDRXed grains with an average grain size of 8.5–8.8 μm, while Zn-2Cu-0.5Mg and Zn-2Cu-1Mg alloys were almost composed of completed DRXed grains with an average grain size of 4.2–6.5 μm. Nanoprecipitates ε-CuZn4 were uniformly precipitated in both DRXed regions and unDRXed regions. Continuous DRX (CDRX) and twinning-induced DRX (TDRX) were the main mechanisms at a low Mg content; Discontinuous DRX (DDRX) and particle-stimulated nucleation (PSN) were strengthened with the addition of Mg. The improved yield strengths in Zn-2Cu-xMg originate from grain boundary strengthening, Orowan strengthening, and hetero-deformation-induced (HDI) strengthening. The fracture elongations are mainly affected by the synergistic effect of bimodal grains, non-basal < c + a > dislocations, and the secondary phases.

Enhancing strength and γ’-coarsening resistance through micro-alloying additions to an oxidation resistant Al-Co-Cr-Fe-Ni-Ti compositionally complex alloy

The effect of alloying additions of Mo and Ta (0.4at.% each) on the microstructure, mechanical properties, oxidation resistance and coarsening resistance of the L12-strengthened (γ’) Al-rich Ni51Co18Fe5Cr10Al12Ti4 alloy was determined. The micro-alloyed composition exhibited improved yield strength (from room temperature to 1000 °C) and coarsening resistance (enhanced by 33% at 800 °C) compared to the base Ni51Co18Fe5Cr10Al12Ti4 alloy. The present Al-rich alloy compositions (both the micro-alloyed and reference compositions) exhibited superior oxidation resistance (800-1000 °C) compared to a Ti-rich Ni51Co18Fe5Cr10Al8Ti8 alloy (with similar precipitate volume fraction and (Al+Ti)-content) and commercial Inconel 718. The present work highlights the promise of Al-rich γ’-strengthened Al-Co-Cr-Fe-Ni-Ti alloys as candidates for high-performance, high-temperature structural materials, characterised by an attractive blend of strength, resistance to coarsening, and resilience against oxidation.

Strengthening mechanisms in vanadium-microalloyed medium-Mn steels

In this work, the impact of adding vanadium, ranging from 0 to 2 wt%, on the microstructure and mechanical properties of as-cast medium manganese steel was explored. A dual phase microstructure consisting of martensite and retained austenite was observed in the 0 V, 0.05 V and 0.8 V conditions. The 2 V condition contained retained austenite, lath martensite, and δ-ferrite bands. The retained austenite fraction and prior austenite grain size initially increased at lean vanadium concentrations but significantly dropped at the highest vanadium concentration. The element distribution in the constituent phases was investigated in detail. Mn, C and Si partitioning to austenite was observed in the 0 V, 0.05 V and 0.8 V conditions. V and C segregation to the grain boundaries and significant grain refinement were evident in the 2 V condition. The findings also revealed that increasing the vanadium content led to an increase in the hardness of the steel. This assessment was validated by tensile testing, which showed an improvement in yield and tensile strength of the steel with increasing vanadium content, and were supported by reconstruction of the parent austenite grains employing martensitic structures. Finally, the influence of different strengthening mechanisms on the yield strength of as-cast, microalloyed medium-manganese steels was also discussed in terms of simulated stacking fault energy, as well as the quantitative contributions from solid solution, grain boundary, and precipitation strengthening mechanisms.

Evolution of mechanical properties and microstructure of selective laser melted AlSi10MgMn alloy with different post heat treatments

This study investigated the effects of various post heat treatments on the mechanical properties and microstructure evolution of an AlSi10MgMn alloy containing 0.5 wt% Mn produced by the selective laser melting process for the first time. The microstructures under different conditions were analyzed using optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. In the as-manufactured (F) condition, the alloy exhibited an ultimate tensile strength (UTS) of 486 MPa, a yield strength (YS) of 299 MPa, and an elongation of 10.3 %. After a T5 treatment, the UTS and YS increased to 532 MPa and 386 MPa, respectively, resulting in a remarkable 30 % improvement in YS compared to the F state. The tensile properties achieved by the new alloy were considerably higher than those reported for conventional AlSi10Mg alloys in the F, T5, and T6 conditions. The T5 treatment promoted the precipitation of a large fraction of Si-rich nanoparticles and MgSi-based precipitates without disrupting the Si-rich network. After a T6 treatment, the Si-rich network completely disappeared, and the main strengthening phase was MgSi-based precipitates accompanied by α-Al(Mn,Fe)Si dispersoids induced by the Mn addition. Using microstructure-based constitutive models, the strengthening contributions of various microstructural components to mechanical strength in different processing conditions were analyzed.

Experimental study on strengthening steel-truss bridge diagonal members using carbon-fibre-reinforced polymer bonding methods

This study investigated the effectiveness of carbon fibre-reinforced polymer (CFRP) materials in strengthening the diagonal tension members of steel-truss bridges. Monotonic tensile and cyclic loading tests were performed on CFRP-strengthened specimens with variations in the CFRP-bonding range on the flanges. This study focused on the strengthening methods A and B, which were proposed to address insufficient CFRP anchoring near gusset plates by bonding CFRP sheets to both sides of the flanges of the diagonal tension members. The results of the monotonic tensile loading tests indicated a significant increase in tensile stiffness and substantial improvements in yield strength (27%) and ultimate load-bearing capacity (51%) when the strengthening methods A and B were employed. Delamination of the bonded CFRP sheets was effectively delayed, occurring only after the steel yielded, owing to the use of a ductile adhesive (polyurea putty). On the other hand, the cyclic loading tests demonstrated a significant enhancement in the load-bearing capacities (33% for tensile, 32% for compressive) of the strengthened specimens. Moreover, the energy dissipation capacities of the specimens strengthened by methods A and B exhibited linear increases, with 12% and 14% higher values respectively than those of the non-strengthened specimen. Although the stiffnesses (tensile and compressive) of the strengthened specimens decreased in each loading loop, the strengthening methods A and B maintained the stiffness values at approximately 35% higher than those of the non-strengthened specimen.

Research on the shear band suppression mechanism in strut-based lattice structures by oblique graded design

Under compressive loads, shear band formation in lattice structures can lead to stress fluctuations, resulting in a decrease in energy absorption capacity. To specifically suppress shear bands, it is necessary to expound the formation mechanisms. This study used theoretical analysis, experiments, and finite element (FE) simulations to elucidate the mechanism underlying shear band formation in strut-based lattice structures. It was determined that stress concentration at strut joints along the 45° diagonal plane induced shear deformation. Shear bands were most pronounced along the four body diagonals, and their existence diminished as the distance from the diagonal increased. Therefore, a design of oblique graded lattice structure (OGLS) was proposed, and quasi-static compression experiments were performed using FE method. The results showed that the main internal stress of OGLS is combined with the original 45° shear stress and the annular staggered stress produced by the oblique graded design, which constrains each other and avoids mutual dislocation deformation, thus realizing shear band suppression. However, an excessively large graded coefficient excessively weakens the 45° shear stress and results in the appearance of an annular compact band. By optimizing the graded coefficient based on the deformation consistency of the outer contour, the optimized OGLS exhibited significant improvements in yield strength, plateau stress, and energy absorption, which are increased by 36.06%, 39.29%, and 34.41%, respectively. This research offers novel perspectives on how lattice structures can attain stable compression deformation and a high energy absorption capacity.

Flux enhancement with titanium or vanadium oxides addition for superior submerged arc welding of HSLA steel plates

A high-strength low-alloy (HSLA) steel plate of 10 mm thickness underwent submerged arc welding with enhanced fluxes containing additional titanium oxide (TiO2) or vanadium oxide (V2O5). The addition of TiO2 led to the development of a finer acicular ferrite structure but coarsening the carbide and martensite/austenite (M/A) constituents, which marginally improved the hardness, tensile strength, and ductility of weld metal. Conversely, incorporating V2O5 facilitated a substantial vanadium absorption (0.7 wt. %) in the weld metal, giving rise to a distinctive acicular microstructure less reliant on ferrite nucleation at non-metallic inclusions than conventional acicular ferrite. The distinctive microstructure, unique to vanadium steels, combined lath bainite with irregularly shaped granular bainite. The resultant dual-mode bainitic structure, coupled with a more uniform distribution of refined microphase constituents, outperformed the conventional acicular ferrite, delivering more than 20% and 13% improvements in yield and tensile strengths respectively, as evidenced by transverse tensile tests on the weld metals.

Physio-mechanical and tribological characterisation of sintered aluminium 7068 modified with NiTiFeAlCu high-entropy-alloy for engineering applications

ABSTRACT Metal particles are gaining attention as reinforcement in metal matrix composites owing to their ductility as compared with ceramic particles, which are inherently brittle. High-entropy-alloy (HEA) particles belong to this category based on their high strength, ductility, and thermal stability. Aluminium-7068 is a new aerospace alloy in the 7000 series that possesses higher strength than aluminium-7075, yet very few studies have considered reinforcement with high-entropy alloy particles. For strength improvement, NiTiFeAlCu (HEA) powder was introduced into the aluminium-7068 matrix at 0, 4, 8, and 12 wt. % at 500 °C via vacuum sintering. The microstructure depicted dispersed particles in the matrix with a linear reduction in porosity as the HEA dosage increased. Consequently, there was a linear increase in density and relative density. 4–12 wt.% HEA engendered linear improvements in yield and ultimate tensile strength, elastic modulus, and hardness; meanwhile, elongation was a progressive decline. The outcome of this study shows that HEA particles in AA-7068 resulted in an improvement of the tensile and hardness properties. The particle addition was observed to reduce the composite’s friction coefficient and wear rate. This report revealed that the performance of AA-7068 can be improved up to 12 wt. % NiTiFeAlCu HEA addition.

Role of carbon on the enhanced strength-ductility synergy in a high-entropy alloy by multiple synergistic strategies

A new Fe47Mn31Co10Cr10C2 high-entropy alloy (HEA) was developed to investigate the role of carbon in enhancing the strength-ductility synergy by utilizing multiple synergistic strengthening strategies with mitigating the adverse effect of carbon. Compared with the Fe40Mn40Co10Cr10 twinning-induced plasticity (TWIP) HEA, the carbon-doped Fe47Mn31Co10Cr10C2 HEA after annealing at 1173 K for 10 min exhibited a higher strain-hardening rate, and significantly improved yield strength (YS) and ultimate tensile strength (UTS), with maintaining high elongation. The remarkable improvements in YS were mainly attributed to the multiple synergistic strengthening mechanisms, including enhanced grain boundary strengthening, hetero-deformation-induced (HDI) strengthening, and Cr23C6 precipitation strengthening. The higher strain-hardening rate could be ascribed to the enhanced TWIP effect and HDI strain-hardening. The effective stacking fault energy (SFE) of the Fe40Mn40Co10Cr10 and Fe47Mn31Co10Cr10C2 HEAs were calculated by thermodynamics to be 23.4 mJ/m2 and 22.1 mJ/m2, respectively. This revealed that reducing the Mn content effectively counteracted the increasing effect of carbon on the SFE for the carbon-doped HEA. The promotion of deformation twinning in the Fe47Mn31Co10Cr10C2 HEA could be ascribed to the comprehensive effect of the SFE and the stress levels of the alloys. On one hand, compared with the Fe40Mn40Co10Cr10 TWIP HEA, the lower SFE in the Fe47Mn31Co10Cr10C2 HEA led to a drop in the critical stress for deformation twinning. On the other hand, due to the strong multiple synergistic strengthening with carbon doping, the stress levels of the alloys were significantly enhanced, thus making the activation stress of twinning much easier to achieve. This study contributes to the alloy design guidance of properly utilizing carbon to achieve high strength-ductility synergy in alloys by multiple synergistic strategies.

Fatigue behavior of polymethyl methacrylate/acrylonitrile butadiene styrene blends including blend composition, stress ratio, frequency, and holding pressure effects

In engineering applications, polymer materials are expected to exhibit superior fatigue life and balanced mechanical properties as essential performance criteria. The blending method is an important alternative in improving the performance criteria of ABS polymer in service. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and Dynamic Mechanical Analysis (DMA) methods were used for characterization. The effects of the PMMA fraction on the mechanical and fatigue behavior of PMMA/ABS blends were investigated by tensile and fatigue tests. Also, the influence of blend composition, stress amplitudes, stress ratio, holding pressure, and loading frequency on fatigue life is considered. The study improved yield strength, tensile strength, and elongation at break values of blends compared to ABS. In addition, 115 % and 75 % improvements were achieved in fatigue cycles at high and low-stress amplitudes with blends, respectively, for tension/tension loading. Similar improvements were obtained for fully reverse loading at 218 %. Thus, it was determined that the PMMA/ABS blend exhibited superior fatigue life in both tension/tension and fully reverse loading situations. Finally, it has been understood that PMMA/ABS blends can be designed to have mechanical properties and fatigue life behavior that can meet different requirements in conditions for engineering applications.

Design of Quenching and Tempering Process and Elucidation of the Relationship between Microstructure and Properties of 20Mn2SiNiMo Bainitic Wheel Steel

The rapid development of train transportation toward higher speed and heavier load requires superior wheel materials with high strength and toughness. Herein, a 20Mn2SiNiMo bainitic wheel steel is developed and bainitic wheels are produced. The quenching and tempering process of bainitic wheels is studied considering the bainitic ferrite content and stability of retained austenite (RA). The quenching process includes water spraying and air cooling. Proeutectoid ferrite can be suppressed during the water‐spraying process. During air cooling, the bainitic ferrite transformation is promoted and the stability of RA is improved with the extension of cooling time. Corresponding microstructure of as‐quenched steel at wheel rim is bainite with different morphologies, martensite, and RA. The evolution of RA at lower and higher tempering temperatures is dominated by carbon enrichment and carbon consumption, respectively. Yield strength of bainitic wheel steel mainly comes from body‐centered cubic phase (containing martensite and bainitic ferrite). The increase of dislocation density and the decrease of effective grain size are beneficial for yield strength improvement. Bainitic packets with various direction, deformation‐induced martensite transformation of RA, and plastic deformation all play an important role in enhancing the toughness of bainitic wheel steel.

Microstructure, mechanical properties and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x= 0, 0.5, 1.0) Y alloys

Microstructure, mechanical properties, and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x = 0, 0.5, 1.0) wt.% Y series alloy have been investigated using microstructure observation, microhardness testing, tensile testing, immersion tests, and electrochemical measurements in simulated body fluid (SBF). The results show that the second phase's type, volume fraction, and distribution change with Y microalloying in the Mg–Ca–Zn alloys. The Mg–2Zn-0.3Ca (alloy 1) mainly comprises α-Mg and Ca2Mg6Zn3 phases. However, the amount of the Ca2Mg6Zn3 phase gradually decreases, and phases I (Mg3YZn6) and W (Mg3Y2Zn3) are also formed in Mg–2Zn-0.3Ca-0.5Y (alloy 2) and Mg–2Zn-0.3Ca–1Y (alloy 3), respectively. Furthermore, an increase in Y content to 1% refines the grains of alloy 1 leading to the improvement of microhardness (66.7 ± 4.2 HV), yield strength (141 ± 7 MPa), and ultimate tensile strength (385.7 ± 18 MPa) in alloy 3. The coarse and discontinuous eutectic phases (α-Mg + Ca2Mg6Zn3) in alloy 1 leads to accelerating the galvanic corrosion near the grain boundary. Moreover, polarization tests show that the addition of the rare earth element Y up to 0.5% in the alloy 2 leads to decreased corrosion current density (4.04 × 10−3 A cm−2) and the best anti-corrosion property as the result of formation of a protective corrosion product film.

Effect of Mg/Si ratio on synergistic improvement of formability and yield strength in Al-Mg-Si-Zn alloys

The design of Al-Mg-Si-Zn series alloys combines the advantages of 6xxx and 7xxx series alloys and breaks through the limitations of strength and formability matching of traditional alloys. In this study, we achieved an exceptional strength-formability combination in the Al-0.84Mg-0.79Si-3.38Zn (wt.%) alloy. Following a solution treatment at 550 °C for 3 min, the alloy exhibited an elongation of ∼36.8%, with a yield strength of ∼356 MPa after artificial aging at 175 °C for 8 h. The effects of different Mg/Si ratios (∼0.6, ∼1.2, and ∼2.5, at.%) on the strength-formability interplay in Al-Mg-Si-Zn alloys were investigated. The alloy with a low Mg/Si ratio (∼0.6) facilitated the precipitation of fine β'' phases characterized by a high number density (∼8.4 nm−3 × 10−5). A Mg/Si ratio of ∼1.2 proved advantageous for precipitating larger β'' phases with a higher volume fraction (∼0.69%), resulting in an elevated precipitation strengthening effect (∼290 MPa). However, with an increase in the Mg/Si ratio to ∼2.5, the reduced availability of Si atoms for forming Mg-Si clusters led to a decrease in the number density of precipitates. Additionally, the interaction among Fe, Mn, and Si elements resulted in the presence of blocky α-Al(FeMn)Si phases, as opposed to the needle-like β-AlFeSi phases, in the alloy with a Mg/Si ratio of ∼1.2. This effectively prevented the degradation of elongation. Our findings present a comprehensive strategy for the compositional design of high-performance aluminum alloys.

Semi-Solid Forging Process of Aluminum Alloy Connecting Rods for the Hydrogen Internal Combustion Engine

As an important piece of equipment for hydrogen energy application, the hydrogen internal combustion engine is helpful for the realization of zero carbon emissions, where the aluminum connecting rod is one of the key core components. A semi-solid forging forming process for the 7075 aluminum alloy connecting rod is proposed in this work. The influence of process parameters, such as the forging ratio, sustaining temperature, and duration time, on the microstructures of the semi-solid blank is experimentally investigated. The macroscopic morphology, metallographic structure, and physical properties of the connecting-rod parts are analyzed. Reasonable process parameters for preparing the semi-solid blank are obtained from the experimental results. Under the reasonable parameters, the average grain size is 41.48~42.57 μm, and the average shape factor is 0.80~0.81. The yield strength and tensile strength improvement ratio of the connecting rod produced by the proposed process are 47.07% and 20.89%, respectively.

A comprehensive investigation on the effect of SiCp on microstructure and mechanical properties of Mg–5Sb-based hybrid composites

Microstructural development, strengthening mechanisms, and mechanical properties of the newly developed Mg–5Sb-xSiCp (x = 0, 1, 3, and 5) composites were studied in both as-cast and extruded states. The microstructures of composites were composed of α-Mg, in-situ Mg3Sb2, and SiCp phases. The cooling curves display that Mg3Sb2 intermetallics form as the primary phase. During solidification, the SiCp acts as heterogeneous sites for both α-Mg and intermetallics formation. The increase in SiCp content (from 0 % to 5 %) modified the as-cast grain size from 827 μm to 411 μm with the improvement of yield strength (YS) (74–97 MPa). Also, the SiC addition to as-cast facilitates the formation of a randomized texture and a significant reduction in intensity from 13.121 mrd to 6.301 mrd for SiC-Free and 5 wt% added MMCs, respectively. Grain refining and recrystallization are characterized by electron backscatter diffraction (EBSD) analysis. Grain refinement via SiCp and hot extrusion leads to substantial structural refinement, resulting in a decrease in grain size from about 411 μm down to 3.92 μm for MMC with 5 wt% of SiC. Consequently, the best combination of the ultimate tensile strength (UTS) (∼244 MPa) and total elongation (∼8.9 %) was obtained for the hot extruded composite containing 3 wt% SiCp. The prevailing strengthening mechanisms are supposed to be particle strengthening mechanism in the as-cast condition and coefficient of thermal expansion (CTE), Orowan, and Hall-Petch mechanisms in the as-extruded condition. Obviously, adding SiCp and employing hot working lead to significant increase in ultimate compressive strength (from 180 MPa to 321 MPa for 5 wt%).

An efficient approach to manufacturing carbon nanosheets from lignite and their impact on the mechanical performance of semi-crystalline thermoplastic composites with comprehensive benchmarking

Lignite-derived carbon nanosheets (CNS) offer a novel approach to producing carbon-based nanomaterials with unique advantages over other precursors. The primary mechanism successfully demonstrated the transformation of lignite into CNS by thermo-chemical treatment process through acid treatment (HNO3), catalyst impregnation (FeCl3), and carbonization (1000 °C, 5 min) steps resulting in the enrichment in the carbon content by maintaining the desired efficiency to be used as a filler in compounding process. Moreover, the produced CNS had superior characteristics in terms of carbon content reached 70 % and thermal stability even at 1000 °C compared to lignite. Subsequently, a comprehensive benchmarking study was conducted to achieve high compatibility and uniform dispersion between semi-crystalline thermoplastics such as HomoPP, CopoPP, PA6 and PA6,6 with CNS using a high-speed thermokinetic shear mixer. CNS exhibited enhanced compatibility with thermoplastics, leading to improved mechanical properties such as tensile and flexural modulus inpolymer composites. The benchmark studies revealed that a loading ratio of 0.5 wt% of CNS exhibited optimal reinforcement efficiency. Notably, PA6 matrix demonstrated the most significant improvement in yield strength, increasing by 12 %, while PA6,6 showed the highest increase in tensile modulus at 25 %. Similarly, PA6,6 exhibited the most notable improvement in flexural modulus with a substantial increase of 17 %. Conversely, HomoPP matrix displayed the highest improvement in flexural strength, increasing by 13 %. Furthermore, the incorporation of CNS into the polymer leads to an increase in the crystallization temperature from 182 °C to 194 °C for PA6-0.5 % CNS. These findings highlight the potential of CNS as versatile materials with promising polymer applications such as automotive and aviation.