Increase In Yield Strength Research Articles

The Synergy Reinforcement Effect of Sm0.85Zn0.15MnO3 and ZrMgMo3O12 on Sm0.85Zn0.15MnO3-ZrMgMo3O12/Al-20Si Composites.

Negative thermal expansion (NTE) ceramics Sm0.85Zn0.15MnO3 (SZMO) and ZrMgMo3O12 (ZMMO) were selected to prepare Sm0.85Zn0.15MnO3-ZrMgMo3O12/Al-20Si (SZMO-ZMMO/Al-20Si) composites using ball milling and vacuum heating-press sintering processes in this study. The synergistic effect of the SZMO and ZMMO NTE ceramic reinforcements on the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of the composites was investigated. The results show that the processes of ball milling and sintering did not induce the decomposition of SZMO or ZMMO NTE ceramic reinforcements, nor did they promote a reaction between the Al-20Si matrix and SZMO or ZMMO NTE ceramic reinforcements. However, the excessive addition of SZMO and ZMMO NTE ceramics led to their aggregation within the composite. Adding a small amount of SZMO in combination with ZMMO effectively increased hardness and yield strength while reducing CTE in the Al-20Si alloy. The improvement in strength was primarily provided by SZMO, while the inhibition effect on CTE was primarily provided by ZMMO. An evaluation parameter denoted as α was proposed to evaluate the synergy effects of SZMO and ZMMO NTE ceramic reinforcements on the mechanical properties and CTE of the composites. Based on this parameter, among all composites fabricated, adding 2.5 vol% SZMO NTE ceramic and 10 vol% ZMMO NTE ceramic resulted in an optimal balance between CTE and strength for these composites with a compressive yield strength of 349.72 MPa and a CTE of 12.55 × 10-6/K, representing a significant increase in yield strength by 79.20% compared to that of Al-20Si alloy along with a notable reduction in CTE by 26.44%.

Reduced graphene oxide (rGO) reinforced CoCrFeNiMn high entropy alloy: Microstructure, mechanical properties, and corrosion behavior

The CoCrFeMnNi high entropy alloy (Cantor), and its variant incorporating 0.2 wt% reduced graphene oxide (rGO), denoted as Cantor + rGO, were successfully synthesized using mechanical alloying followed by spark plasma sintering. Comprehensive characterization utilizing FESEM, XRD, and TEM provided detailed insights into the microstructural features of the materials. The addition of rGO reduced crystallite size from 209 nm to 169 nm, promoted a uniform distribution of carbide phases of smaller size, and enhanced microhardness from 421.8 HV to 510 HV for Cantor and Cantor + rGO, respectively. The incorporation of rGO into the Cantor structure led to an increase in compressive yield strength (CYS) from 1100 MPa for Cantor to 1250 MPa for Cantor + rGO sample. A significant decrease in corrosion current density of samples from 6.1 ± 1.5 μA/cm2 for Cantor to 1.4 ± 0.9 μA/cm2 for Cantor + rGO was observed due to the addition of rGO reinforcement. Moreover, the pitting corrosion resistance was increased in rGO-reinforced Cantor, as revealed by cyclic polarization test. This research underscores the potential for utilizing rGO as a reinforcing agent to optimize the mechanical and corrosion resistance characteristics of HEAs, offering promising avenues for advanced materials in diverse applications.

Microstructure-Based Modeling of Deformation and Damage Behavior of Extruded and Additively Manufactured 316L Stainless Steels.

In this study, we investigated the micromechanical deformation and damage behavior of commercially extruded and additively manufactured 316L stainless steels (AMed SS316L) by combining experimental examinations and crystal plasticity modeling. The AMed alloy was fabricated using the laser powder bed fusion (LPBF) technique with an orthogonal scanning strategy to control the directionality of the as-fabricated material. Optical microscopy and electron backscatter diffraction measurements revealed distinct grain morphologies and crystallographic textures in the two alloys. Uniaxial tensile test results suggested that the LPBFed alloy exhibited an increased yield strength, reduced elongation, and comparable ultimate tensile strength in comparison to those of the extruded alloy. A microstructure-based crystal plasticity model was developed to simulate the micromechanical deformation behavior of the alloys using representative volume elements based on realistic microstructures. A ductile fracture criterion based on the microscopically dissipated plastic energy on a slip system was adopted to predict the microscopic damage accumulation of the alloys during plastic deformation. The developed model could accurately predict the stress-strain behavior and evolution of the crystallographic textures in both the alloys. We reveal that the increased yield strength in the LPBFed alloy, compared to that in the extruded alloy, is attributed to the higher as-manufactured dislocation density and the cellular subgrain structure, resulting in a reduced elongation. The presence of annealing twins and favorable texture in the extruded alloy contributed to its excellent elongation, along with a higher hardening rate owing to twin-dislocation interactions during plastic deformation. Moreover, the grain morphology and defect state (e.g., dislocations and twins) in the initial state can significantly affect strain localization and damage accumulation in alloys.

Modifying the Microstructure and Mechanical Properties of Non-Heat Treated HPDC AlSi10MnMg Foundry Alloy via Incorporation of TiB<sub>2</sub> Particles and Sc

The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB2 and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB2. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB2. TiB2 incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al3Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al3Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB2-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Chemical-free Reactive Melt Processing of Biosourced Poly(butylene-succinate-adipate) for Improved Mechanical Properties and Recyclability.

Biosourced and biodegradable polyesters like poly(butylene succinate-co-butylene adipate) (PBSA) are gaining traction as promising alternatives to oil-based thermoplastics for single-use applications. However, the mechanical and rheological properties of PBSA are affected by its thermomechanical sensitivity during its melt processing, also hindering PBSA mechanical recycling. Traditional reactive melt processing (RP) methods use chemical additives to counteract these drawbacks, compromising sustainability. This study proposes a green reactive method during melt compounding for PBSA based on a comprehensive understanding of its thermomechanical degradative behavior. Under the hypothesis that controlled degradative paths during melt processing can promote branching/recombination reactions without the addition of chemical additives, we aim to enhance PBSA rheological and mechanical performance. An in-depth investigation of the in-line rheological behavior of PBSA was conducted using an internal batch mixer, exploring parameters such as temperature, screw rotation speed, and residence time. Their influence on PBSA chain scissions, branching/recombination, and cross-linking reactions were evaluated to identify optimal conditions for effective RP. Results demonstrate that specific processing conditions, for example, twelve minutes processing time, 200 °C temperature, and 60 rpm screw rotation speed, promote the formation of the long chain branched structure in PBSA. These structural changes resulted in a notable enhancement of the reacted PBSA rheological and mechanical properties, exhibiting a 23% increase in elastic modulus, a 50% increase in yield strength, and an 80% increase in tensile strength. The RP strategy also improved PBSA mechanical recycling, thus making it a potential replacement for low-density polyethylene (LDPE). Ultimately, this study showcases how finely controlling the thermomechanical degradation during reactive melt processing can improve the material's properties, enabling reliable mechanical recycling, which can serve as a green approach for other biodegradable polymers.

Strain rate-temperature effects and constitutive models for Q690D QT steel

This paper investigates the mechanical properties of the high-strength structural steel Q690D QT (Quenched and Tempered) over a wide temperature range and a wide strain rate range. Firstly, a series of quasi-static and dynamic tests adopting the universal testing machine and Split Hopkinson Pressure Bar were carried out to investigate the mechanical properties at strain rates from 0.00025 s−1 to 5000 s−1 and temperatures from room temperature (20 °C) to 700 °C. Stress-strain curves and dynamic yield strength increase factors were extracted and investigated. Test results show that Q690D QT exhibits different strain rate effects at different temperatures, more significant at the temperatures of 600 and 700 °C, as well as the high-temperature softening effect. Dynamic strain aging effect is identified at temperatures between 300 − 600 °C for plastic strain rates of 800 s−1 and 2300 s−1, nevertheless, this effect is observed at a higher temperature range of 500–700 °C for higher plastic strain rates of 4000 s−1 and 6400 s−1. From the analysis, the adiabatic thermosoftening effect cannot be ignored when the plastic strain rates reach 4000 s−1. Finally, an improved form of the Johnson-Cook model is proposed for capturing the adiabatic temperature effects at different temperatures and validated by the test data. A parameter dynamic temperature factor is proposed to describe the comprehensive effect of strain rate, test temperature, and adiabatic thermosoftening.

Electropulsing of low-density duplex steel for strengthening and ductilization by microstructural refinement

The present investigation finds the effect of electropulsing treatment on the mechanisms of refining and reprecipitation of ordered L20 structure (B2) and its impact on tensile properties of low-density duplex steel of Fe-18Mn-10.5Al-1 C-6Ni composition. The selected composition without manganese is melted at 1600°C by induction heating in a vacuum but Mn is added into the melt at 1560°C, in the argon atmosphere to reduce the loss. The melt is cast into a plate form in a copper mold. The cast steel is homogenized, hot rolled, and annealed (PD1-A sample) to get elongated bands, spheroids, and platelets of B2 phase with an austenitic matrix which results in a yield strength of 1015 MPa, and tensile strength of 1285 MPa with a plastic elongation of 16.3%. Electropulsing partially dissolves the B2 phase at a temperature much lower than the equilibrium solvus by reducing barrier energy because of electron wind. As a result, the sizes of bands and spheroids are reduced, and platelets are disintegrated. Electron wind force deforms coarse precipitates, and fragments as well as spheroidized it. Electropulsing of annealed steel (PD1-AE) mobilizes dislocations, and recovers it in B2, but induces localized recrystallization of austenite. At a later time of the signal, the temperature rapidly falls and the matrix becomes supersaturated but electropulsing accelerates low-temperature precipitation of the B2 phase. Therefore, electropulsing can be adopted as a fast manufacturing process to dissolve, deform, fragment, spheroidize and reprecipitate high temperature phase at much lower temperature by dominant athermal effect of electron wind energy over thermal effect. Electropulsing also induces recovery and recrystallization at a relatively low temperature and reduces defect density. Reduction in the overall size of B2 and its distribution towards better uniformity provided an increased yield strength of 1077 MPa, tensile strength of 1355 MPa, and a plastic elongation of 21.6%. The selected duplex low-density steel follows two-stage work hardening of Ludwigson model with an additional stage of dynamic recovery. Fractography analysis confirms that both samples show mixed modes of ductile and brittle fracture, with an increase in size and area percentage of dimples.

The Effect of the Iso‐Thermal Heat Treatment on the Microstructure and Properties of Powder Bed Fusion–Laser Beam AlSi10Mg Alloy

The effect of iso‐thermal heat treatments on powder bed fusion–laser beam (PBF–LB) AlSi10Mg alloy has been studied; however, an extensive process–property relationship evaluation has not yet been undertaken. In addition, the coarsening of eutectic Si from low‐to‐high (200–500 °C) temperature heat treatment has not been investigated systematically. Therefore, AlSi10Mg alloy is heat‐treated at 200, 300, 400, and 500 °C for holding times ranging from 0.5 to 32 h. Uniaxial tensile and hardness tests are conducted, and the microstructure is characterized. A unique approach is adopted for estimating Si solubility where 200 °C heat‐treated microstructure data to estimate solute trapping due to the high cooling rate in the as‐fabricated state. It is observed that increasing the heat‐treatment temperature and time reduces the strength and strain‐hardening rate but increases the tensile elongation up to 400 °C heat treatment. At 500 °C, the yield strength increases, and the elongation reduces compared with the 400 °C heat treatment owing to the refined Fe containing dispersoid formation at 500 °C. The important outcome of this study is heat‐treatment process–property contour maps that are useful for fine‐tuning the mechanical properties of PBF–LB AlSi10Mg alloy for industrial prototyping application.

Processing of high-strength thermal-resistant Al-2.2% cerium-1.3% lanthanum alloy rods with high electric conductivity by High Pressure Torsion Extrusion

A novel severe plastic deformation (SPD) process of High Pressure Torsion Extrusion (HPTE) was applied to the rods of the Al-2.2 wt.% Ce-1.3 wt.% La (Al–3.5RE) alloy. The microstructure, microhardness, the mechanical strength, thermal stability, and electrical conductivity of the alloy after HPTE and subsequent annealing have been investigated. It was demonstrated that HPTE processing can simultaneously increase yield strength from 127 to 225 MPa and electrical conductivity from 54.7% IACS to 55.7% IACS in this alloy. Such a remarkable combination of properties was achieved thanks to significant refinement of microstructure constituents: grain size of Al matrix was reduced down to 0.9 µm and initially continuous network of Al11RE3 phase was broken to micrometer- and nanometer-sized particles. Furthermore, the yield strength of the HPTE-processed Al–3.5 RE alloy remains stable at 230 °C for 1 h due to micrometer- and nanometer-sized particles that pin the grain boundaries. Therefore, HPTE processing of Al–RE alloys has a high application potential in the electric power industry.Graphical abstract

Effect of Ag content and extrusion on the microstructure and mechanical properties of Mg–Ag alloys

Recently, the Mg–Ag binary alloy has gained much attention as an antibacterial biomaterial. However, the relationships between the extrusion parameters, microstructure, and mechanical properties of Mg–Ag alloys haven't been clearly established. Therefore, in this paper, the effects of silver (Ag) content (0, 3, 6 wt%) and extrusion (as cast, extrusion ratio (ER) 7.1 and 72.2) on the microstructure and mechanical properties of Mg–Ag alloys are systematically investigated. The results indicate that for the Mg–Ag alloys with the same extrusion ratio, as the Ag increased from 0 to 3 wt%, Mg4Ag and Mg54Ag17 precipitated, leading to significant precipitation strengthening and an increase in the yield strength by over 137%. As the Ag increased to 6 wt%, the yield strength increased by only ∼20%, attributable to Ag promoting dynamic recrystallization, resulting in less grain refinement, a slower amount increase and a smaller size reduction of the precipitate. For the Mg–Ag alloys with the same Ag content, as the extrusion ratio increased to 7.1, the yield strength increased significantly by over 37%, since the grain boundary strengthening and precipitation strengthening were significantly enhanced as the grains were refined, a large number of precipitates appeared, and their sizes significantly reduced. When the extrusion ratio increased to 72.2, the yield strength increased by only ∼10%, due to the weakening of both grain boundary strengthening and precipitation strengthening as the recrystallization further improved, leading to an increase in grain sizes, the redissolution of precipitates, and a lesser reduction in their sizes.

Effect of Ti additions on the mechanical properties and thermal expansion properties of Ni9Cr9Co9Fe9Tix (x=1, 2, 3) high entropy alloy

The mechanical properties and thermal expansion properties of high entropy alloys (HEAs) are crucial for practical applications. However, there is a scarcity of research on how to optimize the relationship between the mechanical and thermal expansion properties, which currently restricts the application of HEAs as precision structural materials. To address this critical issue, the present study investigates the mechanical properties and thermal expansion properties of Ni9Cr9Co9Fe9Tix (x=1,2,3) HEAs fabricated via repeated arc melting and casting in a vacuum environment. The results show that Ni9Cr9Co9Fe9Tix HEAs exhibit a typical microstructure characteristic of dendritic and inter-dendritic phase, and a small amount of Ni3Ti phase is formed in the Ni9Cr9Co9Fe9Tix HEAs. The addition of Ti notably increases the tensile strength of Ni9Cr9Co9Fe9Tix HEAs, while the presence of the Ni3Ti phase contributes to a reduction in its thermal expansion coefficient. Notably, HEAs with higher Ti content demonstrate increased yield strength but diminished ductility. The primary mechanisms that strengthen the HEA are solid-solution strengthening, secondary phase hardening and dislocations strengthening of the FCC matrix. This study provides superior mechanical properties for HEAs structural components and reduces the thermal expansion coefficient of the matrix alloy, which also indicated the potential of this material for the design and development of HEAs for precision structural components.

Effects of Chemical Composition and Cross-Linking Degree on the Thermo-Mechanical Properties of Bio-Based Thermosetting Resins: A Molecular Dynamics Simulation Study.

Bio-based epoxy resins have received significant attention in terms of concerns regarding carbon emission. Epoxidized soybean oil (ESO) derived from sustainable feedstock has been widely used to blend with traditional diglycidyl ether of bisphenol-A (DGEBA) to replace some of the petroleum-based components. In this work, molecular dynamics (MD) simulations were applied to track the network formation and predict the performance of methyl hexahydrophthalic anhydride (MHHPA)-cured ESO/DGEBA blend systems. The effects of ESO content and cross-linking degree on the mass density, volumetric shrinkage, glass transition temperature (Tg), coefficient of thermal expansion (CTE), Young's modulus, yield strength, and Poisson's ratio of the epoxy resin were systematically investigated. The results show that systems with high ESO content achieve gelation at low cross-linking degree. The Tg value, Young's modulus, and yield strength increase with the increase in cross-linking degree, but the CTE at the glassy state and Poisson's ratio decrease. The comparison results between the simulated and experimental data demonstrated that the MD simulations can accurately predict the thermal and mechanical properties of ESO-based thermosets. This study gains insight into the variation in thermo-mechanical properties of anhydride-cured ESO/DGEBA-based epoxy resins during the cross-linking process and provides a rational strategy for optimizing bio-based epoxy resins.

Thermo-kinetic understanding of the correlation between bainitic transformation and mechanical properties for bainitic steels

Phase transformations are feasible approaches for tailoring microstructures to achieve desired mechanical properties. However, the direct link between phase transformations and mechanical properties remains poorly studied. Here, using the theory of generalized stability (GS), we theoretically and experimentally correlate the bainitic transformation with the mechanical property of bainitic streels from a thermo-kinetic perspective. We established a quantitative relationship between the thermodynamic driving force and the yield strength, and explored the underlying physical correlation between the GS and the ductility. It is demonstrated that the thermodynamics-kinetics trade-off in the bainitic transformation inherently leads to the mutually exclusive relation between the yield strength and the uniform elongation. Specifically, a higher driving force generally results in an increased yield strength, while a larger GS tends to yield improved uniform elongation. Our findings provide fundamental insights into the relationship between the thermo-kinetics of bainitic transformation and mechanical properties, offering potential guidance for designing bainitic transformations to directly achieve superior mechanical performances.

Anisotropic behavior and temperature-dependent mechanical properties of AA1060 aluminum alloy: A comprehensive microstructural study

This study rigorously examines the AA1060 aluminum alloy's mechanical properties across different thermal conditions (298K–77K) and orientations (RD-ND and TD-ND). Through annealing at 350 °C for 50 min followed by extensive mechanical testing at ambient and cryogenic temperatures, the study delves into the microstructural evolution and deformation mechanisms utilizing Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM). Findings indicate a pronounced increase in yield strength, tensile strength, and ductility with decreasing temperature. Notably, RD-ND oriented samples demonstrated enhanced mechanical strength over TD-ND oriented samples under both temperature regimes, underscoring the alloy's pronounced anisotropy. This comprehensive study illuminates the AA1060 alloy's temperature-dependent mechanical enhancements and anisotropic behavior, emphasizing the significant impact of microstructural orientation on its mechanical properties. The insights gained illuminate the AA1060 alloy's temperature-dependent and anisotropic behaviors, highlighting microstructural orientation's important role in its mechanical properties, with profound implications for aluminum alloy application across varying temperature and stress conditions.

Possibility of application of the ARDS method for obtaining permanent joints of composite materials reinforced with highly dispersed phase of titanium carbide obtained on the basis of aluminum-magnesium alloys

Subject of research: the evaluation of the possibility of using the argon arc welding method (ARWM) to obtain unbreakable joints of composite materials AMg2-10%TiC and AMg6-10%TiC. Purpose of research: obtaining welded joints by argon-arc welding with a non-consumable electrode based on aluminum matrix composite materials AMg2-10%TiC and AMg6-10%TiC using filler rod grade 5356 and comparing the structure and properties of AMKM welded samples with welded samples of AMg2 and AMg6 matrix alloys obtained using the same methods modes. Methods of research: studies were carried out to control visible and hidden defects, metallographic analysis, as well as an assessment of the mechanical properties of welded joints. It has been established that the level of ARDS weldability of composite materials AMg2-10%TiC and AMg6-10%TiC is at the level of ARDS weldability of matrix alloys AMg2 and AMg6. Main results of research: it is shown that when using the ARDS method it is possible to dislocate reinforcing particles of titanium carbide in composite materials AMg2-10%TiC and AMg6-10%TiC from the base metal zone to the heat affected zone as well as to the weld zone. It was found that the presence of welded joint in composite material AMg2-10%TiC leads to an increase in hardness and yield strength.

Microstructural features and mechanical properties of spray -formed hypereutectic Al-Si-Ti alloy

ABSTRACT In the present study, the effect of the addition of Ti on the microstructural and mechanical properties of hypereutectic (Al/15 wt. %Si) spray-formed (SF) alloys has been investigated and compared with as-cast (AC) alloys. Al/15Si and Al/15Si/2Ti alloys were synthesised by spray forming method. The microstructural features of the alloys were explored under an optical microscope, and a scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis were carried out for phase identification. The phase analysis confirmed the presence of α-Al and Si phases in all the alloys, with additional peaks attributed to Al3Ti and AlSi2Ti present in the Al/15Si/2Ti alloys. The microstructure of the SF1 alloy (Al/15Si) consisted of globular, fine Si phases (primary and eutectic) distributed homogeneously in the equiaxed Al matrix. The addition of Ti to the binary SF1 alloy led to the formation of an SF2 alloy (Al/15Si/2Ti) with a fine intermetallic phase of Al3Ti and further spheroidisation of Si particles. The SF1 and SF2 alloys exhibited 30% and 40% greater microhardness, respectively, than did their corresponding AC alloys. With the addition of Ti, the ultimate tensile strength of the SF2 alloy increased by 19% compared to that of the SF1 alloy. Furthermore, a significant increase in yield strength and ductility was observed in the SF alloys compared to the AC alloys. Adding Ti to hypereutectic Al/15Si alloy via the spray-forming method provides a better alternative material for aerospace and automotive applications.

Experimental and numerical investigation on out-of-plane ultimate strength of high-strength steel arches

This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches.

Strengthening mechanism and interaction between nano precipitates and defects in wrought Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd alloys

Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd (x = 2.4, 6) alloys were subjected to multi-directional forging (MDF). The β1 coherent phase and β incoherent phase precipitated during the MDF process significantly improve the properties of the alloy. The results show that the orientation relationship between the β1 phase and the matrix is 022β1∥0002α and 111β1∥12¯10α.When the dislocations cut through the β1 phase, the {111} 〈110〉 slip system of the β1 phases is activated, forming anti-phase boundaries (APBs) by directional motion in the <110> direction, which provides strengthening effects. The APB structure leads to the increase of system energy, deformation resistance, and yield strength. Besides, the activation of the β1 phases slip system makes the alloys exhibit satisfactory plasticity and toughness. After MDF at 350 °C, Mg-5Li-1Zn-0.5Ag-0.5Zr-2.4Gd alloy has a yield strength of 270 MPa, a tensile strength of 295 MPa, and an elongation of 12.7%, respectively. The results are beneficial for the design and manufacture of high-performance MgLi alloys.

Enhanced mechanical properties of magnesium alloy reinforced by layered Ti3AlC2 MAX phase fabricated by SPS at a near solidus temperature

Powder metallurgy stands out as a highly promising and versatile method for manufacturing particle-reinforced metal matrix composite (MMCs) as compared to other fabrication processes. This method ensures excellent binding between the matrix and reinforcement, uniform microstructure, and effectively prevents the formation of undesirable phases. In this study, magnesium alloy (AZ91) metal matrix composites (MMCs) reinforced with 0–30 vol% of Ti3AlC2 MAX phase were prepared by Spark Plasma Sintering (SPS) from powders at temperature close to the solidus. Ti3AlC2 is a member of the MAX phases which are known for their layered structure, machinability and being ternary carbides. The latter was synthetized from pure components (Ti, TiC and Al) using insulated SPS technology at high temperature. Sintered composites reached quasi-full density, as measured by Archimedes’ method. Their microstructure has been assessed by SEM and X-ray diffraction (XRD) respectively. Mechanical properties in relationship with the microstructure of all composites were carefully investigated. The experimental compressive tests data were extracted to obtain true strain-true stress curves. Vickers hardness (HV1), ultimate compressive strength (UCS) and conventional yield strength (0.2%YCS) increase with an increasing fraction of Ti3AlC2 in the composites and compare favorably with literature. SEM observations of fracture surfaces after compression tests seem to show that cracks initiate in both Ti3AlC2 clusters and α-Mg/MAX interfaces.

Achieving excellent strength and ductility of Ti2ZrNbHfVx refractory high-entropy alloys by V addition

Refractory high-entropy alloys (RHEAs) have gained considerable attention owing to their excellent mechanical properties. In this study, the combined effects of vanadium (V) on the microstructure, mechanical properties, and strengthening mechanism of Ti2ZrNbHfVx (x= 0, 0.2, 0.4, 0.6, 0.8, and 1, respectively) are investigated. The results indicate that all Ti2ZrNbHfVx alloys present a BCC single phase with a typical dendritic microstructure. The yield strength (YS) increase with the increasing V content. Among them, the Ti2ZrNbHfV RHEA has a YS of up to 1008 MPa, a compressive strain of >50%, and a specific yield strength (SYS) of 134.20 KPa·m3·kg−1. Furthermore, the Vickers hardness increases from 230.23 to 328.80 HV. High YS is mainly derived from solid-solution and fine-grain strengthening. The YS of Ti2ZrNbHfVx RHEAs is mostly obtained from atomic radius and shear modulus misfits, according to the solution strengthening model. The present study provides not only a solution for achieving a strength-ductility synergy but also insights into the development of RHEAs with excellent mechanical properties.