Yield Strength Of Matrix Research Articles

Effect of graphene on microstructure, strain hardening and corrosion behaviour of dual phase Mg-Li matrix processed through liquid metallurgy route

The significance of this study lies in the potential enhancement of magnesium (Mg)-based materials through the addition of graphene, aiming to improve their mechanical properties and corrosion resistance. This research investigates the development of graphene-Mg composites, employing a liquid metallurgy route to fabricate a dual-phase structured Mg-8Li composite. Mg-Li dual-phase composites are of interest due to their lightweight nature and promising mechanical properties, making them suitable for applications in aerospace, automotive, and structural engineering. Graphene was incorporated into the Mg matrix at varying percentages (0.2, 0.4 and 0.6 wt.%), and the resulting materials were subjected to microstructural, mechanical, and corrosion analyses. Microstructural characterization results reveals that the increase in graphene content results in decrement in grain size of α-Mg and β-Li up to ∼33 and ∼11.5% respectively. Likewise, additions of graphene improvise tensile and yield strength of base matrix up to ∼47 and ∼44% respectively. Strain hardening exponent (n) values of base material decrease from 0.21 to 0.17 with respect to graphene addition which confirms the effect of graphene that acts as effective barrier to slip that decreases the deformation. Corrosion analysis revealed a decrease in corrosion rate and increased pitting resistance with the addition of graphene, indicating improved corrosion resistance. Electrochemical impedance spectroscopy results depict that the composite with 0.4 wt.% graphene exhibits larger semi conducting loop with higher charge transfer resistance ( Rct) value of 128 Ω cm2.

Microstructure evolution and enhanced mechanical performance of multilayer MXene-reinforced silver matrix composites

In this study, multilayer MXenes were first incorporated into an Ag matrix through a hetero-agglomeration process followed by spark plasma sintering (SPS), with the microstructural evolution of MXenes during composite fabrication characterized using transmission electron microscopy. The partial decomposition of MXene and transformation into rutile-TiO2 nanoparticles occurred during SPS, facilitating the generation of submicron Ag grains through effective pinning. As revealed by the Vickers hardness measurements and tensile tests, the addition of 3 vol% MXene increased the hardness and yield strength of the Ag matrix from 57.7 HV and 97.5 MPa to 116.0 HV and 129.1 MPa, representing increases of 101 % and 32 %, respectively. Quantitative calculations suggested that the improved mechanical properties of the MXene/Ag composites were primarily due to grain refinement strengthening. Meanwhile, the electrical and thermal conductivities of the 3 vol% MXene/Ag composite decreased by 9 % and 11 %, respectively. However, the ultimate tensile strength and ductility of the composites were lower than those of pure Ag, attributed to the weak MXene-Ag interfacial bonding and fracture surface observations, as well as the presence of accordion-like structures in MXene. Compared with conventional Ag matrix composites, MXene/Ag composites demonstrate a superior balance of mechanical and physical properties, making them highly suitable for applications in electrical devices. This work enhances our understanding of the interface phenomena between MXenes and metals, providing new insights for designing novel Ag matrix composites for use in conductive devices.

Enhanced mechanical properties of Ni3Al composites reinforced with single-walled and multi-walled carbon nanotubes: An atomistic modeling study

In this study, the mechanical properties of a Ni3Al matrix composite reinforced with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were investigated using atomistic modeling. The analysis focused on the behavior of the composite under uniaxial tensile strain across a range of temperatures (100–900[Formula: see text]K). The results demonstrated that the incorporation of any type of carbon nanotubes (CNTs) significantly enhanced Young’s modulus, yield strength, and tensile strength of the Ni3Al matrix. Notably, the reinforcement with MWCNTs resulted in superior mechanical properties compared to SWCNTs. Additionally, an increase in temperature led to a reduction in Young’s modulus for all composite samples. Among the tested configurations, the composite reinforced with MWCNTs exhibited the highest tensile modulus and yield strength, outperforming both the SWCNT-reinforced composite and the unreinforced Ni3Al crystal. These findings underscore the potential of MWCNTs as effective reinforcements in improving the mechanical performance of Ni3Al-based composites, especially at elevated temperatures.

Effect of surface rolling process on rolling contact fatigue behavior and failure mechanism of powder metallurgy steel

The effect of surface rolling process on the surface microstructure and rolling contact fatigue of the Fe-2Cu-0.6 C powder metallurgy steel was investigated in the present investigation. Results indicated that a densified and hardened layer with a densification depth of 330 μm and a surface hardness of 330 HV0.1 was generated in the surface layer after rolling process. Ferrite grain and pearlite lamellae became typical fibrous structures on the top surface. The microstructure of pearlite was presented by two typical features. One was that the discrete cementite plates were severely curled and wavy. The other one was that the cementite plates remained parallel to each other, but were a reticular structure at a macroscopic level. The rolling contact fatigue (RCF) test showed that the RCF life of the rolled sample was superior. The L10, L50, L63.2 life increased by 182%, 105%, 92%, respectively. Surface initiated spalling was the main fatigue failure mode. Subsurface equivalent contact stress and local equivalent stress were calculated. The results showed that surface cracks were due to the repetitive tensile stress, which caused pits. Subsurface cracks nucleated and propagated in the region where the local equivalent stress was higher than the matrix yield strength, which caused spalling as connecting with surface cracks. The surface densified layer plays an important role in improving the rolling fatigue resistance of the material.

Surface shot peening of cast SiCw/Al composites

ABSTRACT The surface shot peening treatment was carried out on the as-cast SiCw/Al composites, and the distribution of the residual stresses in the surface matrix was measured, the X-ray diffraction method for the yield strength of the surface matrix of the composites was established to explore the strengthening effect of the surface shot peening. The results show that the surface matrix of the composites after shot peening shows a large compressive residual stress state, and the FWHM, that is, the microstructure strengthening effect, is significantly increased., resulting in an increase in the yield strength of the surface matrix of the composites.

Complex-inclusion induced fracture mechanism of ultraclean 100Cr6 bearing steel under high cycle fatigue test

Fatigue property of an ultraclean 100Cr6 bearing steel was investigated by the high-cycle rotating bending fatigue tests. It was found that the cyclic loading below 1197 MPa led to the frequent cracking initiated from the complex inclusions with the two distinctly different features: the breaking and the debonding of complex inclusions, all of them have a core of oxide agglomerate containing many cavities and a nearly 2 μm-thick sulfide shell. Finite element simulation results reveal that this distinction depends on whether a sufficiently high residual stress (RS), which should be developed near the interface of inclusion and matrix during quenching and accumulated during the cyclic loading, can exceed the yield strength (YS) of steel matrix. Higher interfacial RS than the YS leads to the debonding of inclusion whilst lower one to the breaking of inclusion. A more uniform and thicker sulfide shell could relieve the RS to the greater extent, favoring the breaking of inclusion with longer fatigue life. Finally, we propose that the critical sizes for no fatigue crack initiated at the pure oxide, the complex inclusions with non-uniform and uniform sulfide shell are 11.2 μm, 12.8 μm and 17.0 μm respectively, and the optimum size ratio of oxide core to the entire complex inclusion is 0.56–0.76. Both are of great importance on tailoring the inclusions of ultraclean bearing steel for improving the fatigue life of bearing steel.

Elucidating the mechanical response and microstructure evolution of the constituent layers in gradient-structured Cu alloys

The design of gradient structure (GS) in metallic materials has been reported to obtain superior mechanical properties due to the interaction between the GS layer and the coarse-grained (CG) matrix. In this study, the mechanical response and microstructural evolution of the corresponding constituent layers of GS Cu-4.5Al alloy at different pre-strains were systematically investigated. The tensile results showed that the strain hardening capability of the GS layer was improved due to the constraint of the CG matrix. Meanwhile, an extra strengthening was observed at the interface between the GS layer and the CG matrix, resulting in a higher yield strength of the CG matrix constrained by the GS layer than that of the CG matrix without the GS layer constraints. Moreover, the extra strengthening at the interface of the GS and CG matrix was gradually reduced with increasing pre-strain due to the weakening of the interaction at the interface. Microstructural observations at the interface between the GS layer and the CG matrix revealed that more dislocations and twins were activated during pre-strain in the CG matrix having GS constraints than that of the CG matrix without GS constraints. The present work provides important insights on the interaction between constituent layers, in terms of the mechanical response and microstructure evolution.

Effect of Ti6Al4V reinforcement particles on the mechanical, wear, and corrosion properties of AZ91D magnesium matrix composites

This study aims to synthesize composite materials using TC4 particles and AZ91D alloy through semi-solid stirring and hot extrusion techniques. The main objective is to investigate the microstructure, mechanical properties, wear resistance, and corrosion behavior of composites comprising a minor volume fraction (0, 2, and 5 vol%) of spherical TC4 particles. The findings showed that the dual synergistic effect of TC4 particles and the β-phase leads to a refinement in the grain size of the composite material. Moreover, the incorporation of TC4 particles enhances the hardness, yield strength (YS), and ultimate tensile strength (UTS) of the magnesium matrix, with almost no reduction observed in ductility. Additionally, the TC4/AZ91D composite displays lower wear rates and friction coefficients compared to the matrix when subjected to forces of 150 N and 300 N. However, the corrosion performance of the composite material deteriorates due to the influence of the galvanic effect between the particles and the matrix.

Theoretical prediction method of Young's modulus and yield strength of micron particle reinforced metal matrix composites at different temperatures

To begin with, a theoretical characterization model of temperature and porosity dependent Young's modulus for micron particle reinforced metal matrix composites is established by considering the evolution of properties of reinforced particles and metal matrix with temperature. Additionally, combining the existing strengthening mechanism theory and incorporating the influence of grain boundary slip on the related strengthening mechanism and the yield strength of metal matrix, a temperature dependent yield strength analysis model of micron particle reinforced metal matrix composites is proposed. These models only require material parameters at room temperature and temperature dependent specific heat capacity at constant pressure for application. In addition, the predicted results from these models are reasonable and consistent with measured results. Moreover, based on the established models, the effects of key material parameters and main mechanisms on Young's modulus and yield strength of composites and their variation with temperature are explored. Furthermore, the variation of various control mechanisms with the particle size and temperature is clarified. It lays a theoretical foundation for the development of micron particle reinforced metal matrix composites that are suitable for high-temperature environments and for the optimization of their key parameters.

Strain Partitioning and Frictional Behavior of Opalinus Clay During Fault Reactivation

The Opalinus Clay (OPA) formation is considered a suitable host rock candidate for nuclear waste storage. However, the sealing integrity and long-term safety of OPA are potentially compromised by pre-existing natural or artificially induced faults. Therefore, characterizing the mechanical behavior and microscale deformation mechanisms of faults and the surrounding rock is relevant for predicting repository damage evolution. In this study, we performed triaxial tests using saw-cut samples of the shaly and sandy facies of OPA to investigate the influence of pressure and mineral composition on the deformation behavior during fault reactivation. Dried samples were hydrostatically pre-compacted at 50 MPa and then deformed at constant strain rate, drained conditions and confining pressures (pc) of 5–35 MPa. Mechanical data from triaxial tests was complemented by local strain measurements to determine the relative contribution of bulk deformation and fault slip, as well as by acoustic emission (AE) monitoring, and elastic P-wave velocity measurements using ultrasonic transmissions. With increasing pc, we observe a transition from brittle deformation behavior with highly localized fault slip to semi-brittle behavior characterized by non-linear strain hardening with increasing delocalization of deformation. We find that brittle localization behavior is limited by pc at which fault strength exceeds matrix yield strength. AEs were only detected in tests performed on sandy facies samples, and activity decreased with increasing pc. Microstructural analysis of deformed samples revealed a positive correlation between increasing pc and gouge layer thickness. This goes along with a change from brittle fragmentation and frictional sliding to the development of shear zones with a higher contribution of cataclastic and granular flow. Friction coefficient at fault reactivation is only slightly higher for the sandy (µ ~ 0.48) compared to the shaly facies (µ ~ 0.4). Slide-hold-slide tests performed after ~ 6 mm axial shortening suggest stable creeping and long-term weakness of faults at the applied conditions. Our results demonstrate that the mode of fault reactivation highly depends on the present stress field and burial history.

On the yield criterion of two-scale porous materials by using Eshelby-type velocity field and Steigmann–Ogden surface model

In this work, we investigate the yield strength of porous metallic materials in the presence of both microvoids and nanovoids. A two-level hierarchical model composed of both microscopic and macroscopic representative volume elements (RVEs) are proposed for this purpose. The lower level RVE is made up of an incompressible, perfectly elastoplastic, von Mises matrix and multiple dilute nanovoids. By using a micromechanics-based homogenization method, a microscopic yield criterion is first established in terms of the overall equivalent stress, uniaxial yield strength of the microscopic matrix, Gurtin–Murdoch and Steigmann–Ogden nanovoids surface constants, as well as the microscopic porosity. The lower level RVE is then treated as a material point in the upper level RVE matrix. The macroscopic dissipation rate is evaluated from the conventional deviatoric strain rate used in Gurson’s classical criterion, an Eshelby-type exterior velocity field and the compressibility rate of the macroscopic matrix. Closed-form solutions are eventually determined for such a velocity field and the macroscopic yield function, by simultaneously satisfying the arbitrary macroscopic strain rate boundary conditions and enforcing the principle of minimum dissipation rate. Compared to similar criteria available in the literature, two distinct features can be identified. First, the full version Steigmann–Ogden surface model is considered on nanovoids surface. Second, both the hydrostatic and deviatoric deformation of the microvoid are considered in the velocity field. Extensive parametric studies are conducted to investigate the effects of nanovoids surface bulk modulus, surface shear modulus, surface flexural rigidity, nanovoids radius, and both levels of porosities on the macroscopic yield loci. The results obtained in this article are helpful to the better design and manufacturing of nanoporous metallic materials.

Thermomechanical Characterization of E‐Glass Fiber Reinforced Random Polypropylene

AbstractThe thermomechanical properties of short glass fiber (GF) reinforced polypropylene random copolymer (PPR) composites are investigated. Four composites with different fiber content, namely 10, 15, 20, and 30 wt%, are prepared using melting mixing. For fibers up to 15 wt% the composites exhibit enhanced thermal stability as compared to the random polypropylene. The use of fibers also improve the mechanical strength of the matrix. In particular, PPR/GF30% demonstrates the highest Young modulus, yield strength, and storage modulus values, while PPR/GF10% has the best ductility among the composites. Incorporation of 10 wt% fibers also increases the yield strength and storage modulus of the PPR matrix by approximately 1.6 and 1.2 (for temperatures higher than 60°C) times, respectively. These results suggest that GF reinforced PPR is a composite suitable for advanced technological applications.

Behaviors and interactions of strengthening and constraint for ductile Nbss matrix in Nb–Si based alloys

The ductile matrix in composites could be strengthened by incorporating brittle inclusions, while the constraint effect for matrix would become more obvious and detrimental to material toughening. The balance between strengthening and toughening was crucial to achieve excellent comprehensive mechanical properties. Upon the basis of microstructure of Nb–Si in situ composites, a unit rectangular cell containing elastic and isotropic Nb5Si3 particles was modeled, the Niobium solid solution (Nbss) matrix according with the Ramberg-Osgood constitutive relation was recognized as elastic-plastic. For Nb–Si based alloys, the effects of volume fractions of Nb5Si3 reinforcements, stress states and interfacial characteristics on the stress-strain field, flow localization and damage evolution were investigated by the finite element method (FEM). Further, the normalized work of rupture (χ) was calculated quantitatively as a function of volume fractions of Nb5Si3 phase as well as yield strength of Nbss matrix. These results would contribute to acquire more fundamental understanding of the strengthening and constraint effects which were exerted by Nb5Si3 reinforcements to ductile Nbss matrix, also an instructive guidance for the optimum design of Nb–Si based alloys.

High-performance copper-matrix materials reinforced by nail board-like structure 2D Ti3C2Tx MXene with in-situ TiO2 particles

Two-dimensional (2D) nanomaterials based on MXenes have gained increasing importance in the field of strength reinforcement. However, the easy oxidation of MXenes has long been deemed unfavorable for reinforcement in high-temperature processing. Herein, high-shear mixing was used in present work for simple and efficient dispersion of MXenes in copper powders. Partial MXene sheets were also in-situ oxidized to TiO2 particles to form nail board-like structure reinforcement (NSR) during spark plasma sintering (SPS) process at 600 °C, which allowed one to significantly improve the yield strength of copper matrix by up to 70.3%. Experimental characterization and modeling simulations enabled one to identify second phase strengthening as the main reason for increased yield strength of the composites. In particular, the mechanical engagement of NSR played an important role in strengthening. Meanwhile, the hardness of TiO2 particles on NSR was found to be higher than that of the copper matrix, leading to enhancement in compressive yield strength. Also, the presence of MXene sheets on NSR slightly reduced the resistance of copper matrix composites. In sum, these findings look promising for designing novel MXene reinforced metal matrix composites with improved mechanical properties.

Designing co-reinforced in-situ (Cr3C2(w) + Cr2O3(p))/CoCrFeNi composite with excellent strengthening efficiency

A process is developed for fabricating in-situ CoCrFeNi matrix composite co-reinforced with Cr3C2 whiskers and Cr2O3 nanoparticles. Initially, mechanical alloying of the powder was carried out to obtain powder containing laminates of FCC and thin Cr rich layers along with carbon dispersed at the laminate interfaces. The powder was then reaction sintered as the Cr layers reacted with carbon and transformed into Cr3C2 phase. Concomitantly, a uniform precipitation of Cr2O3 nanoparticles took place across the microstructure. The designed microstructure exhibited excellent reinforcement efficiency and a yield strength of over 1 GPa along with elongation of 12% was achieved. According to the calculation based on strengthening mechanism models, the reinforcements were estimated to be responsible for a more than 100% increase in matrix yield strength.

Investigations on Mechanical Behaviour of Micro B4C Particles Reinforced Al6061 Alloy Metal Composites

Objective: To develop and evaluate the mechanical behavior of 3, 6, 9 and 12 wt. % of B4C reinforced Al6061 alloy composites. Method: These composites were produced by utilizing stir cast process. The prepared metal composites were characterized by SEM, EDS and XRD analysis to know the distribution of particles as well as presence of particles in the Al6061 alloy. Various mechanical properties were evaluated as per ASTM standards to know the impact of boron carbide particles on the properties of metal composites. Findings: By adding B4C particles the hardness, ultimate tensile, yield strength and compression strength of the Al6061 alloy matrix was enhanced 23.9%, 15.4 14.9% and 34.7% respectively. Further, there was slight decrease in the percentage elongation of B4C reinforced composites. Novelty: In the present research Al6061 alloy with 3 to 12 wt. % of B4C composites were synthesized by novel stir casting method called as two stage reinforcement addition process. In this process 80 micron sized boron carbide particles added in two stages into the molten Al6061 alloy to improve the wettability between the matrix and reinforcement particles. Keywords Al6061 Alloy, B 4 C Particles, Hardness, Tensile Strength, Microstructure

Numerical investigation on the variation of compressive failure mechanisms in unidirectional carbon fiber reinforced polymer

This paper presents a study on the variation of compressive failure mechanisms in carbon fiber reinforced polymer (CFRP) as well as the effects of material properties and structure parameters on the compressive strength in different failure mechanisms. A two-dimensional microscale model is developed to simulate numerically the compressive process of CFRP with local structure imperfections. The fiber kinking can be induced by either the interfacial failure or the matrix yielding depending on the interfacial strength of carbon fibers. CFRP with lower interfacial strength can exhibit wider kink band. Higher Young’s modulus of matrix, yield strength of matrix or misalignment level causes the failure mechanisms variation to occur at higher interfacial strengths, while the fiber diameter affects the failure mechanism variation in the opposite way. Furthermore, the compressive strength is found to be sensitive to the variation of matrix properties in the matrix-driven failure and to the fiber diameter in the interface-driven failure. These findings indicate that the strategies for the compressive strength enhancement can be different according to the compressive failure mechanisms.

Increasing Necking Strain through Corrugation: Identifying Composite Systems That Can Benefit from Corrugated Geometry.

Under some circumstances, composites with a corrugated reinforcement geometry show larger necking strains compared to traditional straight reinforced composites. In this work, finite element modeling studies were performed for linearly hardening materials, examining the effect of material parameters on the stress–strain response of both corrugation and straight-reinforced composites. These studies showed that improvements in necking strain depend on the ability of the corrugation to unbend and to provide a boost in work hardening at the right time. It was found that there is a range of matrix yield strengths and hardening rates for which a corrugated geometry will improve the necking strain and also a lower threshold of reinforcement yield strength below which no improvement in necking strain is possible. In addition, benefit maps and surfaces were generated that show which regions of property space benefit through corrugation and the corresponding improvement in necking strain that can be achieved.

A physically-based constitutive model for the shear-dominated response and strain rate effect of carbon fibre reinforced composites

A significant hardening response is often observed for the shear-dominated deformation of Carbon Fibre Reinforced Plastics (CFRP). This non-linear response is typically modelled by fitting a strain hardening law against experimental stress-strain curves. Inspired by crystal plasticity framework, we develop a micro-mechanically motivated constitutive model to capture the matrix shearing and fibre rotation of CFRP under finite strain deformation and different strain rates. Strain rate dependency of the shear modulus and yield strength of the matrix was modelled through scaling functions. This physically-based constitutive model is first verified by simple shear and transverse compression tests, followed by comprehensive validations against the measured stress-strain responses of unidirectional (UD) and cross-ply composite laminates subjected to quasi-static and dynamic off-axis loading. The finite element predictions and analytical models of CFRP lamina under simple shear loading confirms that the initial yielding is governed by the shear yield strength of matrix, while the hardening behaviour is dependent on the modulus and rotation of carbon fibres. This model accurately predicts the non-linear behaviour of CFRP under off-axis loading at different strain rates, without the need of a curve-fitted strain hardening law.

Mechanical and Wear Behaviour of Severe Plastic Deformed Al6063-Nano Al2O3 Composites Processed by Constrained Groove Pressing (CGP)

Metal matrix composites have been developed to meet the demand for lighter materials with high specific strength, stiffness and wear resistance. Particulate reinforced aluminium matrix composites are attractive materials due to their strength, ductility and toughness. The aluminium matrix is strengthened when it is reinforced with hard ceramic phases. Most of the metal matrix compound undergoes severe plastic deformation (SPD). SPD is a method to obtain fine crystalline structure in different bulk metals and alloys which possess different crystalline structure. The objective of the present work is to synthesize Al-6063 alloy by stir casting method and varying weight percentage of nano Al2O3 in steps of 2, 4, and 6 wt %. The composites are prepared using the process of compressed groove pressing (CGP) with extreme plastic deformation. The composite is characterized for mechanical and wear behaviour. SEM microphotographs confirmed the distribution of nano Al2O3 particles in the Al6063 Matrix alloy. In addition, SEM micrographs of Al6063 alloy with nano Al2O3 after constrained groove pressing shown grain refinement. Improvements in Hardness, UTS, yield strength, bending strength, percentage elongation and wear resistance of the Al-6063 matrix are obtained with the addition of Al2O3 particulates and also the properties are further enhanced with CGP. The developed metal matrix nano composite may be an alternative material for manufacturing of bearings.