Evolution Of Elastic Modulus Research Articles

Microstructure to magnetic properties and nanoindentation mapping of mechanical properties relationship in amorphous and partially crystallized Fe–Si–B–P-type alloy

Microstructure, crystallization behavior, magnetic properties as well as nanoindentation mapping of mechanical properties were studied for amorphous and partially crystallized Fe72Co6Si4B9Mo1P8 alloy. X-ray diffraction accompanied by transmission electron microscopy studies confirm amorphicity of the as-quenched precursor, and complex nature of the material annealed at 873 K for 0.5 h. The primary at Tx1 = 766 K and secondary at Tx2 = 880 K crystallization temperatures were derived from DSC curve. Moreover, Curie points of 646 K and 1032 K for amorphous and crystalline phase created during heat treatment process, respectively, were also determined. Investigations of the magnetization versus temperature in zero field cooled mode allowed to determine Curie points for the amorphous and partially crystallized Fe72Co6Si4B9Mo1P8 alloy, as well as magnetic behavior of the investigated samples. Single phased and dual phased structures described by different mechanical properties for amorphous and annealed samples were confirmed by distribution maps of mechanical parameters. The as-quenched material is characterized by hardness of HVIT= (1050.31 ± 41.63) Vickers, elastic modulus of EIT= (107 ± 5) GPa and elastic deformation energy to total energy ratio of nIT= (46.68 ± 1.06) %. After annealing at 873 K bimodal distributions of mechanical parameters were observed. Evolution of hardness and elastic modulus as a function of penetration depth shows that with increasing of load both HVIT and EIT decrease. Moreover, elastic modulus for the amorphous and partially crystallized sample calculated for maximum load of 250 mN are almost the same.

Evolution of elastic moduli through a two-dimensional structural transformation

We use a classical analytical and separable elastic energy landscape describing SnO monolayers to estimate the softening of elastic moduli through a mechanical instability occurring at finite temperature in this material. Although not strictly applicable to this material due to its low-energy barrier $J$ that leads to a quantum paraelastic phase, the present exercise is relevant as it establishes a conceptual procedure to estimate such moduli straight from a two-dimensional elastic energy landscape. As additional support for the existence of a quantum paraelastic phase, we carry a qualitative WKB analysis to estimate escape times from an individual well on the landscape; escape times increase exponentially with the height of the barrier $J$. We also provide arguments against an additional transformation onto a planar lattice due to its high-energy cost. These results continue to establish a case for the usefulness of soft matter concepts in two-dimensional materials, and of the potential lurking of quantum effects into soft matter.

Cyclic hardening/softening behavior of 316L stainless steel at elevated temperature including strain-rate and strain-range dependence: Experimental and damage-coupled constitutive modeling

In this study, the cyclic mechanical characters of 316L stainless steel at elevated temperature are extensively investigated by the experimental and cyclic constitutive models. The experiments include the monotonic tensile tests with different loading rates and the low cycle fatigue tests considering the effect of strain amplitudes, strain rates and loading sequences. The evolution of cyclic stress amplitudes, hysteresis loops and elastic modulus under various loading conditions are comprehensively analyzed. The experimental results show that the 316L steel at elevated temperature performs a typical three-stage cyclic mechanical response, i.e., initial hardening, subsequent saturation and final accelerated softening. The cyclic softening in both stiffness and flow stress is mainly caused by the nucleation of micro-voids or micro-cracks, and the subsequent coalesce and propagation. Furthermore, although the nearly rate-independent mechanical behavior is observed at monotonic tensile and first several fatigue cycles due to the DSA effect, the cyclic hardening/softening behavior shows a significant strain-rate and loading history dependence. Finally, inspired by the experimental observations and analyses, a damage-coupled cyclic elastic-viscoplastic constitutive model involving strain-range, strain-rate and loading history dependence is proposed to predict the complex cyclic behaviors of the material at elevated temperature. A hardening factor is incorporated into the Chaboche kinematic hardening equations to model the kinematic-induced hardening behavior. And the plastic strain memory surface and the maximum plastic strain rate are introduced to model the strain-range, strain-rate and loading history dependence of cyclic behavior. The proposed model is proved to effectively describe the complex evolution of not only cyclic stress amplitude but also hysteresis loops for the 316L steel at elevated temperature.

Mechanical properties of poly(lactid acid) plasticized by cardanol derivatives

This work is aimed to study the effect of cardanol derived plasticizers on the tensile modulus of poly(lactic acid), PLA. Neat cardanol, cardanol acetate (CA), and epoxidized cardanol acetate (ECA) were used, at contents ranging between 10% and 30%. For comparison purposes, another green plasticizer, poly(ethylene glycole) (PEG), was used. Tensile tests were carried out to evaluate the influence of the type and the amount of plasticizer on the tensile modulus of injection molded PLA. Within the examined composition limits, PLA plasticized by cardanol derivatives showed lower modulus than PEG plasticized PLA. The tensile modulus of plasticized PLA was correlated to the evolution of glass transition temperature and degree of crystallinity. At low plasticizers content, the modulus of PLA decreased as the glass transition temperature decreased, due to a better miscibility of the plasticizer with PLA. The opposite occurred at high plasticizer content; in this case, the higher modulus found for more compatible plasticizers were attributed to an increased crystallization kinetic. The evolution of elastic modulus as a function of glass transition temperature and degree of crystallinity was analyzed using a single equation capable to fit the data obtained using different plasticizers.

(Invited) Chemomechanical Behavior of Composite Electrodes in Li-Ion Batteries: Experiments and Modeling

The chemomechanical behavior of composite electrodes is largely different from that of single particles or mono-phase materials. The stress field, state of charge, and mechanical failure are strongly affected by the local details of the microstructure. On the experimental side, we study the structural disintegration of NMC cathode materials of a hierarchical structure by tracking the microstructural evolution of different marked regimes. Decohesion of primary particles constitutes the major mechanical degradation which results in the loss of connectivity of the conductive network and impedance increase. We employ operando nanoindentation to measure the evolution of elastic modulus, hardness, and interfacial strength of NMC cathodes at different states of charge and different cycles. We further use home-developed computational program to investigate the chemomechanical behavior of NMC composites in reconstructed 3D models. An ample space of design is open for the optimization of the capacity and mechanical performance of electrodes by tuning the size, shape, and pattern of active particles, as well as the properties of the inactive matrix.

Elastic modulus deterioration index to identify the loosened zone around underground openings

In order to effectively identify the loosened zone around underground openings by using continuum modeling, this paper proposes an index called elastic modulus deterioration index based on the following two steps. First, the response of surrounding rock mass in underground openings as obtained from ultrasonic tests before and after excavation is investigated. Based on the attenuation of the P-wave velocities of the rock mass after excavation compared to the P-wave velocities before excavation obtained from ultrasonic tests, an index (χ) is defined to assess the excavation-induced rock mass damage. Second, by introducing an empirical relationship between the static and dynamic elastic moduli, the index χ is modified to represent the static elastic modulus evolution, volume change, and stress redistribution of the rock mass based on an elasto-plastic numerical model. Furthermore, this study verifies the performance of the elastic modulus deterioration index to identify the loosened zone around underground openings by comparing its predictions with the results from ultrasonic testing of the loosened zones around two tunnels in the Jinping II hydropower station. The comparisons show that the loosened zones as identified by the elastic modulus deterioration index agree well to those from ultrasonic testing. Analysis of the effects of key input parameters and initial shear strength parameters on the elastic modulus deterioration index in identifying the loosened zone demonstrate that: (1) the sensitivity of the index to the key input parameters except the residual static elastic modulus is not significant; and (2) the index has better fault tolerance performance compared to the indices based on plastic zone in terms of the selection of initial shear strength parameters.

Stress-induced elastic modulus evolution in metallic glasses

In this study, flexible Cu50Zr50 metallic glass fibers (MGFs) with a diameter of 50 μm were prepared by a melt extraction method. The microfibers were axially and radially uniform with a smooth surface. It was found that the elastic modulus of the micron-sized Cu50Zr50 MGFs was low and could increase towards the value of the bulk counterparts with multiple-loading tension. High resolution transmission electron microscopy (HRTEM) experimental observation verified that tensile stress could induce the nanostructural rearrangements in metallic glasses from disorder to short- and medium-range order. Meanwhile, this unique fact was explained by the potential energy landscape with multiple metastable states.

Modeling of natural fiber reinforced composites under hygrothermal ageing

In this paper, we focus on the mechanical performance of fibers naturally derived from plants as reinforcement of a composite structure. A nonlinear constitutive model for the whole hygrothermal ageing process of natural fiber reinforced composites is established. This theoretical model accounts for large elastic and inelastic deformation, diffusion of water molecules and hydrolysis reaction. Based on the non-equilibrium thermodynamic framework, the Helmholtz free energy functions and the corresponding dissipation laws are established. The effects of matrix cracking, fiber-matrix interfacial debonding and change in the microstructure of natural fibers are all considered in this theoretical model. And the competition between the loss and the recovery of mechanical properties of natural fibers is investigated. Moreover, this theoretical model is applied to analyze the elastic response of natural fiber reinforced composites and the influence of ageing temperature is discussed. The obtained theoretical results are compared with corresponding experimental data and it is shown that the present theoretical model is capable of describing the evolution of elastic moduli of composite samples and their temperature dependence during the whole hygrothermal ageing process.

In situ measurement of mechanical property and stress evolution in a composite silicon electrode

Mechanical properties and lithiation-induced stress are crucial to the performance and durability of lithium-ion batteries. Here, we report the evolution of elastic modulus and stress in a silicon/polyvinylidene fluoride (PVDF) composite electrode coated on a copper foil, along with a model for analyzing the large change in the radius of curvature of the composite electrode/copper foil cantilever. The radius of curvature of the cantilever is captured by a video camera during lithiation/delithiation. The elastic modulus of the composite electrode decreases from about 0.64 GPa to 0.18 GPa during lithiation. It decreases further to about 0.10 GPa after delithiation, which is caused by the fracture of the electrode. The magnitude of the compressive stress increases lineally during lithiation and decreases suddenly to reach a steady state value during delithiation.

Microstructural Evolution of NiCoCrAlHfYSi and NiCoCrAlTaY Coatings Deposited by AC-HVAF and APS

The chemical composition of NiCoCrAlHfYSi with a suitable particle size, deposited using an activated combustion-high velocity air fuel (AC-HVAF) spray, is a potentially promising process because dense, continuous and pure alumina can be formed on the surface of the MCrAlY metallic coatings after isothermal oxidation exposure. The NiCoCrAlHfYSi (Amdry386) and NiCoCrAlTaY (Amdry997) coatings were produced using AC-HVAF and APS, respectively. Isothermal oxidation was subsequently conducted at 1050 °C in air for 200 h. This paper compares the characteristics of four coated samples, including the surface roughness, elastic modulus, hardness, oxide content, microstructural characteristics and phase evolution of thermally grown oxides (TGO). The growth of both the TGO and alumina scales in the TGO of the HVAF386 coating was relatively rapid. The θ- to α-alumina phase transformation was strongly determined by the Hf and Si dopants in the HVAF386 coating. Finally, the extent of grain refinement and deformation storage energy in the HVAF997 coatings were determined to be significantly crucial for the θ- to α-alumina phase transformation.

U-drawing of Fortiform 1050 third generation steels. Numerical and experimental results

Elasto–plastic behavior of the third generation Fortiform 1050 steel has been analysed using cyclic tension–compression tests. At the same time, the pseudo elastic modulus evolution with plastic strain was analysed using cyclic loading and unloading tests. From the experiments, it was found that the cyclic behavior of the steel is strongly kinematic and elastic modulus decrease with plastic strain is relevant for numerical modelling. In order to numerically analyse a U-Drawing process, strip drawing tests have been carried out at different contact pressures and Filzek model has been used to fit the experimental data and implement a pressure dependent friction law in Autoform software. Finally, numerical predictions of springback have been compared with the experimentally ones obtained using a sensorized U-Drawing tooling. Different material and contact models have been examined and most influencing parameters have been identified to model the forming of these new steels.

Composition-dependent interdiffusion coefficient, reduced elastic modulus and hardness in γ-, γ′- and β-phases in the Ni-Al system

A combinatorial approach using diffusion couples and advanced characterization was carried out to investigate the composition-dependent interdiffusion and mechanical properties of γ-Ni(Al) solid solution, γ′-Ni3Al and β-NiAl. The diffusion couples between pure Ni and Ni52Al48 were annealed at temperatures of 1000 °C, 1100 °C and 1200 °C for 96 h, 48 h and 24 h, respectively. The γ-Ni(Al), γ′-Ni3Al and β-NiAl have developed in the diffusion zone. The β-NiAl transformed to martensite above room temperature when Al is less than 37 at.%. The composition-dependent interdiffusion coefficients for all phases corresponded closely to previous research. A systematic composition-dependent elastic modulus and hardness for γ-Ni(Al), γ′-Ni3Al and β-NiAl phases were obtained by nanoindentation. Variation of elastic modulus and hardness in the γ-Ni(Al) solid solution is influenced by solid solution strengthening and hardening due to precipitation of γ′-Ni3Al while cooling. The evolution of elastic modulus and hardness in the β-NiAl phase exhibited a minimum value of elastic modulus and hardness near the phase boundary between martensite and austenite. Lattice softening associated with martensitic transformation was recognized to lower the value of elastic modulus and hardness.

Mechanical characterization via nanoindentation of the woven bone developed during bone transport

Nanoindentation has been used successfully in the determination of the mechanical properties of bone. Its application in fracture healing provides information on the evolution of material properties of the woven bone during regeneration process. However, this technique has not been applied in assessing the mechanical properties of woven bone during distraction osteogenesis. Therefore, the aim of this work is to evaluate the spatial and temporal variations of the elastic modulus of the woven bone generated during the bone transport process. Callus samples were harvested from intervened animals at different time points during the bone transport process (35, 50, 79, 98, 161 and 525 days after surgery) for nanoindentation measurements. Results clearly showed that the mean elastic modulus of the woven bone increased during the bone transport process reaching 77% of value for cortical bone after 525 days (from 7GPa 35 days after surgery to 14GPa 525 days after surgery approximately). Woven bone generated during bone transport seems to present similar evolution of elastic modulus with time as values reported for fracture healing. Furthermore, different spatial variations of elastic modulus within the callus were found for different stages of the process.

Influence of molybdenum oxide on structural, optical and physical properties of oxychloride glasses for nonlinear optical devices

Abstract The unconventional Heavy Metal Oxide Glasses (HMOG) are characterized by a low phonon energy, large infrared range transmission, high refractive index and nonlinear optical properties. Ternary glasses have been synthesized and studied in the Sb 2 O 3 – MoO 3 -ZnCl 2 system. Further, the glass formation compositional limits are reported and some glass samples with the formula: (90-x)Sb 2 O 3 -xMoO 3 –10 ZnCl 2 (10 ≤ x ≤ 50, mole%) were elaborated. Thermal properties have been measured and indicating that the glass transition temperature decreases with increasing proportions of molybdenum oxide. The evolution of density, microhardness and elastic modulus has been studied as functions of parameter x and Raman spectra measurements have been shown the partial conversion of MoO 6 octahedral units into MoO 4 tetrahedral.

Relation between mechanical behavior and microstructure of a sintered material for braking application

This paper describes an original methodology to characterize the mechanical properties of sintered materials before and after a realistic braking test bench protocol. This characterization consists in a compression test on different samples extracted from friction pins at different states. The compression tests are instrumented with a Digital Image Correlation (DIC). This technique gives local information allowing to link the strain fields with the microstructural mechanisms of the heterogeneous material. Even if the composition of the friction material is complex, it is shown that it can be summarized, at a mesoscopic scale, as a two-component substance. Moreover, the mechanical behavior can be described with an elastic-plastic hardening model combined with an evolution of the properties as a function of the load level. Comparisons between the unused and used materials exhibit strong differences in the evolution of elastic moduli with loading, which has been associated with damage of the virgin material despite densification of the material after the tests. For the used material, two layers can be distinguished with different mechanical properties. These properties vary with the location on the brake pad, and an explanation of this variation is proposed. Results of this study have demonstrated that it is necessary to consider the evolution of a friction material during a braking sequence rather than only properties in a pristine state as commonly done in the literature. The proposed methodology can be applied to a wide class of materials.

In situ ion induced gelation of colloidal dispersion of Laponite: Relating microscopic interactions to macroscopic behavior

Aqueous dispersion of Laponite, when exposed to CO2 environment leads to in situ inducement of magnesium and lithium ions, which is, however absent when dispersion is exposed to air. Consequently, in the rheological experiments, Laponite dispersion preserved under CO2 shows more spectacular enhancement in the elastic and viscous moduli as a function of time compared to that exposed to air. By measuring concentration of all the ions present in a dispersion as well as change in pH, the evolving inter-particle interactions among the Laponite particles is estimated. DLVO analysis of a limiting case is performed, wherein two particles approach each other in a parallel fashion – a situation with maximum repulsive interactions. Interestingly it is observed that DLVO analysis explains the qualitative details of an evolution of elastic and viscous moduli remarkably well thereby successfully relating the macroscopic phenomena to the microscopic interactions.

Microscale evaluation of laser cladded Inconel 625 exposed at high temperature in air

Ni-based superalloys offer resistance to high-temperature oxidation in different industrial sectors. These alloys can also be deposited as coatings onto metallic substrates by means of different techniques. In this work, a diode laser with carefully selected process parameters was used to generate Inconel 625 coatings onto ferritic and stainless steel substrates. The coatings obtained were exposed to high-temperature treatment in air and different exposition times were studied. The evolution of the coatings microstructure was analysed and depth-sensing indentation tests were performed to measure the evolution of elastic modulus and hardness with the exposition time. Finally, mechanical properties and microstructural changes were correlated. The results revealed that the average mechanical properties and the microstructure of the coatings were not affected by the steel used as the substrate. The treatment at 520°C increased the amount of carbides and brought to the appearance of Laves phases. The treatment at 800°C promoted the formation of mainly δ and Laves phases. These microstructural evolutions involved changes in the values of the mechanical properties of the coatings, which could control their response under operating conditions.

Evolution of macroscopic elastic moduli of martensitic polycrystalline NiTi and NiTiCu shape memory alloys with pseudoplastic straining

Elastic constants of polycrystalline NiTi and NiTiCu shape memory alloys in the martensite phase were determined by resonant ultrasound spectroscopy; the evolution of these constants was studied with subsequent applications of compressive loads inducing reorientation of martensitic variants. While the initial thermally-induced martensite exhibited only weak elastic anisotropy resulting from the underlying crystallographic texture of the parent phase, the materials with oriented martensitic microstructures exhibited strong elastic anisotropy with Young's moduli in different directions differing by several tens of GPa−s. A qualitative difference in behaviors was observed between the monoclinic B19′ martensite in the NiTi alloy and the orthorhombic B19 martensite in the NiTiCu alloy.

Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (1018 cm−2): Their structure and mechanical properties

Multielement high entropy alloy (HEA) nitride (TiHfZrNbVTa)N coatings were deposited by vacuum arc and their structural and mechanical stability after implantation of high doses of N+ ions, 1018cm−2, were investigated. The crystal structure and phase composition were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy, while depth-resolved nanoindentation tests were used to determine the evolution of hardness and elastic modulus along the implantation depth. XRD patterns show that coatings exhibit a main phase with fcc structure, which preferred orientation varies from (111) to (200), depending on the deposition conditions. First-principles calculations reveal that the presence of Nb atoms could favor the formation of solid solution with fcc structure in multielement HEA nitride. TEM results showed that amorphous and nanostructured phases were formed in the implanted coating sub-surface layer (∼100nm depth). Concentration of nitrogen reached 90at% in the near-surface layer after implantation, and decreased at higher depth. Nanohardness of the as-deposited coatings varied from 27 to 38GPa depending on the deposition conditions. Ion implantation led to a significant decrease of the nanohardness to 12GPa in the implanted region, while it reaches 24GPa at larger depths. However, the H/E ratio is ⩾0.1 in the sub-surface layer due to N+ implantation, which is expected to have beneficial effect on the wear properties.

Analyzing aging under oscillatory strain field through the soft glassy rheology model.

In this work, we solve the Soft Glassy Rheology (SGR) model under application of oscillatory deformation field with varying magnitudes of strain as well as frequency for different noise temperatures. In the glassy domain, the SGR model undergoes time evolution of elastic modulus. Increase in strain magnitude beyond the linear regime is observed to enhance the rate of aging as manifested by a faster evolution of elastic modulus with increase in strain amplitude due to overaging. However at higher strain magnitudes, the rejuvenation effect starts dominating over the aging, thereby reducing the rate at which elastic modulus evolves. We also plot the aging phase diagram describing an occurrence of the linear, the overaging, and the rejuvenation regimes as a function of strain and frequency for different noise temperatures. The aging phase diagram suggests that while the linear regime remains unaffected by the changes in frequency and noise temperature, the width of the overaging regime increases with increase in frequency and noise temperature. We also study the time evolution of the shapes of relaxation time spectra as a function of strain amplitude, which renders further insight into the overaging and the rejuvenation behavior. While the phenomenon of overaging is observed to be an inherent character of the SGR model, experimentally not all the materials demonstrate overaging. Such a discrepancy suggests that the energy well depths before and after a yielding event may not be completely uncorrelated as assumed in the SGR formalism.