Stress Relaxation Resistance Research Articles

Preparation and Mechanical Properties Analysis of Rare Earth Filling Ethylene‐Allene Monomer Rubber Composite

AbstractEthylene propylene diene monomer (EPDM) rubber is used in critical sectors such as national defense, military, and aerospace. However, it has performance limitations under high temperatures, affecting its dynamic mechanical properties, creep, and stress relaxation. To overcome these limitations, rare earth cerium oxide (CeO2) was incorporated as a filler into EPDM in this study, which enhances its properties and makes it suitable for the demanding applications. It could be seen that the CeO2‐enriched EPDM has significantly improved mechanical characteristics at elevated temperatures. The Young's modulus of CeO2‐enriched EPDM increased by about 100 %, while the energy storage modulus reaches a maximum increase of around 140 % at 165 °C. The addition of CeO2 improves its damping properties, provides better creep and stress relaxation resistance, and results in greater residual strain recovery. At room temperature, the impact on the stress relaxation rate at 50 % strain is minimal for the material EPDM, and it is almost negligible for the material EPDM/CeO2.These findings demonstrate that CeO2‐enriched EPDM has enhanced performance under high‐temperature conditions. Under elevated temperature conditions, EPDM enriched with CeO2 exhibits enhanced mechanical properties, superior creep resistance, and stable stress relaxation behavior, rendering it more adept at withstanding the rigorous conditions encountered in aerospace applications.

Study of the stress relaxation resistance and microstructural evolution of a Cu–Ni–Si alloy strip

The stress relaxation resistance of a Cu–Ni–Si alloy strip after 48 h of initial loading stress of 80% σ0.2 at 125 °C was studied. The stress relaxation curve was fitted using a model. By employing EBSD, TEM, and other techniques, this study examined the microstructural characteristics of the Cu–Ni–Si alloy strip before and after stress relaxation. This study investigated the stress relaxation mechanism of the alloy and revealed that the stress relaxation rate of the Cu–Ni–Si alloy strip was 10.82% after 48 h at 125 °C. The stress relaxation process of the alloy strip was divided into two main stages. During the first stage, there was a significant rearrangement and movement of dislocations within the alloy strip, leading to a rapid decline in the remaining stress. In the second stage, the interaction among the Ni2Si phase, twins and dislocations led to a slow decrease in the remaining stress. After the stress relaxation of the alloy strip, the precipitated phase in the microstructure grew from 67 nm to 200 nm, the recrystallization microstructure increased from 57.91% to 62.42%, and the twin boundary content decreased from 22.1% to 18.5%. These observed changes in the microstructure are anticipated to further reduce the stress relaxation resistance of the alloy strip.

Effect of trace grain boundary segregation element bismuth on stress relaxation behavior of copper

The stress relaxation resistance of copper-based materials determines the reliability of contact and stable transmission of connector plugs. This study investigates the effect of trace bismuth (110 wt ppm) on the stress relaxation resistance of pure copper at temperatures of 25 °C, 100 °C, and 200 °C. The relationship between microstructure and stress relaxation resistance was analyzed using SEM, EBSD, and HAADF-STEM. The results demonstrate that trace bismuth significantly enhances the stress relaxation resistance of pure copper, especially at higher temperatures of 100 °C and 200 °C, where the stress relaxation rates of Cu-0.011Bi samples after 48 h decreased by 21.36 % and 18.06 %, respectively, compared to Cu samples. Trace bismuth elements exist in copper mainly in the form of double atomic layers segregated at grain boundaries, which pin the grain boundaries, inhibit grain growth, and hinder dislocation slip. At room temperature (25 °C), bismuth mainly improves stress relaxation resistance by refining grains. At higher temperatures of 100 °C and 200 °C, the significant enhancement in stress relaxation resistance is primarily related to bismuth's inhibition of the reduction in dislocation density and recrystallization during the stress relaxation process.

High temperature stress relaxation behavior of high Si, Mo-doped austenitic stainless steels

The resistance to stress relaxation at high temperatures is of importance to fasteners. In this study, the stress relaxation behavior of high Si, Mo-doped austenitic stainless steels at 450, 510, 550, 600 and 650 °C were investigated, taking the microstructure evolution at high-temperature long-term condition into account. It is found that Mo can effectively mitigate the plastic strain rate at high temperatures by impeding the extension of partial dislocations, thus leading to a noteworthy enhancement in the stress relaxation resistance. The first-principles calculations indicated that the addition of Mo can suppress the formation of a multi-phase composed of G phase and ferrite at high temperatures, by increasing the segregation energy of Si, Cr, and Ni at grain boundaries. This multi-phase induces the formation of stacking faults and twins, and therefore is responsible for an abnormal reduction in the residual stress.

Development of eco-friendly and high-content rubberized asphalt modified by waste cooking oil desulfurized crumb rubber and waste crumb rubber

To conserve non-renewable petroleum-based asphalt resources and address the limitations of incorporating high-content waste crumb rubber (CR) in conventional crumb rubber modified asphalt (CRMA), this study examines the feasibility of utilizing waste cooking oil desulfurized crumb rubber (ODR) in conjunction with CR to prepare high-content rubberized asphalt (HCRA). The basic, chemical, rheological, and asphalt-aggregate adhesion properties of HCRA, both with and without a small quantity of styrene-butadiene-styrene (SBS) copolymer modifier, were evaluated using infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), bending beam rheometer (BBR), asphalt-aggregate pull-off test, contact angle test, and atomic force microscopy (AFM). The results showed that the modification involving ODR and CR primarily constitutes a physical process, rather than a chemical reaction, as evidenced by the lack of new functional groups. Similarly, the addition of an SBS modifier predominantly results in physical modifications accompanied by minor chemical interactions. The improved desulfurization degree of ODR diminishes the elastic stiffening effect of CR on the matrix asphalt at the high-temperature (low-frequency) domain and reduces adhesion properties between HCRA and aggregates, while enhancing the flexibility of HCRA at the low-temperature (high-frequency) domain. The inclusion of a small quantity of SBS modifier allows HCRA to demonstrate high-temperature performance and adhesion properties on par with CRMA, alongside superior low-temperature stress relaxation, phase stability, storage stability, and water damage resistance. These attributes indicate that the HCRA with a small quantity of SBS modifier has a broader service temperature range compared to CRMA. This study achieves approximately 33.3 % replacement of asphalt materials while preserving the performance of rubberized asphalt.

Effect of Calefaction and Stress Relaxation on Grain Boundaries/Textures of Cu–Cr–Ni Alloy

The Cu–Cr–Ni alloy is a key material for the manufacturing of connectors, which requires excellent resistance to stress relaxation. However, the inherent correlation among microstructure, texture, and properties is still unclear. In this study, we investigated the influence of calefaction and stress relaxation on the grain boundaries (GBs), textures, and properties of the Cu–Cr–Ni alloy. The results showed that calefaction and stress relaxation had opposite effects on GBs and textures. Calefaction led to a decrease in the proportion of low-angle grain boundaries (LAGBs), an increase in the Schmidt factor (SF) value of the grains, and a transition of texture from <111> to <113>. The grains with higher SF values were more susceptible to plastic deformation, which deteriorated the stress relaxation resistance. By comparison, stress relaxation led to an increase in the proportion of LAGBs, a decrease in SF values of the grains, and a transition of texture from <113> to <111> and <001>. After stress relaxation, the variation trends of the GBs and textures were consistent with those of other plastic deformations, indicating that stress relaxation can be verified by the variations in GBs and textures. Our findings provide a theoretical basis for improvements in stress relaxation resistance of the Cu-based alloys used in connector industry.

The Influence of Aging Temperatures on the Microstructure and Stress Relaxation Resistance of Cu-Cr-Ag-Si Alloy

Copper alloys used in connectors rely significantly on stress relaxation resistance as a key property. In this study, a heavily deformed Cu-Cr-Ag-Si alloy underwent aging at varying temperatures, with a subsequent analysis of its mechanical properties and microstructure, with a particular emphasis on understanding the mechanism of improving stress relaxation resistance. As the aging temperature rose, the Cr precipitated into a Cr-Si composite element precipitated phase. Both work hardening and precipitation strengthening played vital roles in enhancing the stress relaxation resistance of the Cu-Cr-Ag-Si alloy, with the latter exerting a more pronounced impact. The notable performance enhancement observed after aging at 450 °C can be attributed to the synergistic effects of work hardening and precipitation strengthening. Following aging at 450 °C, the alloy demonstrated optimal performance, boasting a tensile strength of 495.25 MPa, an electrical conductivity of 84.2% IACS, and a level of 91.12%. These exceptional properties position the alloy as a highly suitable material for connector contacts.

Study on the microstructure and mechanism of stress relaxation behavior of Cu–Ni–Si alloy by two-stage rolling deformation

In this paper, the effect of the second-stage rolling deformation of Cu–Ni–Si alloy on its stress relaxation resistance was studied, and the mechanism of the change in microstructure and properties before and after stress relaxation was explored. The results show that the tensile strength and yield strength of Two-stage rolling peak aging (TRPA) 43.7 %, TRPA68.8 %, TRPA80.3 % and TRPA96.1 % alloys at 150 °C are close. After stress relaxation, the stress relaxation rates of these alloys are 7.7 %, 11.24 %, 14.69 % and 19.4 %, respectively. It is found that the smaller the second-stage rolling deformation, the better the stress relaxation resistance of the alloy, especially the stress relaxation resistance of the TRPA43.7 % alloy, which is 60.31 % higher than that of the TRPA96.1 % alloy. According to EBSD analysis, it was found that the increase in the number of twins can improve the stress relaxation resistance of the alloy. However, the occurrence of recrystallization reduces the stress relaxation resistance. Additionally, it was determined that the precipitated phase is the δ-Ni2Si phase with an orthogonal structure. Before stress relaxation, the size of the precipitated phase of the alloy with TRPA96.1 % is larger than that of the alloy with TRPA43.7 %, and after stress relaxation, the precipitated phase further grows. The influence of the interface relationship between δ-Ni2Si phase and Cu matrix on the stress relaxation properties of TRPA43.7 % and TRPA96.1 % alloys before and after stress relaxation was investigated using the mismatch theory. In summary, this study reveals that the size of δ-Ni2Si phase, dislocation density and recrystallization are the key factors affecting the stress relaxation resistance of Cu–Ni–Si alloy.

Effect of trace alloying elements on stress relaxation properties of high strength and high conductivity C19160 alloy

The addition of Si in a Cu–Ni–P–Pb (C19160) alloy has been fabricated by atmospheric smelting to approach high strength, high conductivity, and high-stress relaxation resistance. The addition of Si inhibited the coarsening and phase transition of Ni5P4. The fine Ni5P4 particles were dispersed in the matrix, which pinned dislocations and improved the studied alloy's strength and stress relaxation resistance. After homogenization at 900 °C for 4 h, cold rolled by 70 %, aging treatment at 450 °C for 1 h, cold rolled by 60 %, aging treatment at 400 °C for 45 min, cold rolled by 60 %, annealing treatment at 200 °C for 1 h, the C19160-0.1Si alloy shows an ultimate tensile strength of 705 MPa, electrical conductivity of 53.8%IACS, and a stress relaxation rate of 17.8 % after tested at 150 °C for 100 h. These findings have guiding significance for developing C19160 alloys with high strength, high conductivity, and high-stress relaxation resistance.

Poly(epoxy-imine) vitrimers. Effect of the structure on the stress relaxation and creep resistance

A series of polyimine-epoxy vitrimers has been synthesized using commercially available monomers using a two-step synthetic route to maximize the content of imine groups in the resulting structures. The first step consists of the synthesis of amine terminated polyimine oligomers, which were synthesized by a condensation reaction of terephthalaldehyde (TA) with different proportions of diethylenetriamine (DETA) and a polyetheramine (Jeffamine D-230 or D-400). After that, the obtained viscous oligomers were cross-linked with bisphenol A diglycidyl ether (DGEBA). The design of network architectures using this approach is a powerful tool that allows controlling the concentration of imine groups, the dimensions of the intermediate polyimine oligomer and the polarity and mobility of its chains, confirming that it is an effective way to tune the thermal, mechanical and thermomechanical properties of the final materials. Furthermore, this work confirmed that an accurate design of the network architecture allows simultaneously improving the two main requirements of vitrimers by increasing the content of imine groups: fast stress relaxation processes and high creep resistance. Stress relaxation curves proved that these polyimine vitrimers could relax the 63 % of the initial stress in less than 9.6 min at 160 °C without any added catalyst. Besides, replacing Jeffamine D-400 with Jeffamine D-230 in the imine oligomer increases the material's resistance to creep at service temperatures. All the materials prepared present high thermal stability and showed Tgs between 31 and 93 °C.

Evaluation of Modified Asphalt Binders with Soybean Oil-Based Polymers: Preparation Temperature and Rheological Characterization

To investigate the feasibility of bio-based polymers in the modification of base asphalt binder, two soybean oil-based polymers (PAESO) were synthesized from bio-monomers with different functionalities via free radical polymerization. The characterization of both PAESOs was conducted using Hydrogen nuclear magnetic resonance and Gel Permeation Chromatography analyses, the results showed that the bio-monomer with a higher functionality exhibited a stronger tendency towards self-polymerization, resulting in the polymer with a high conversion rate (44.44 %) and a slightly lower molecular weight (14.76 kDa). The optimal mixing temperature for preparing PAESO-modified asphalt binders was determined through Molecular Dynamics (MD) simulation and Laser Scanning Confocal Microscopy. The MD simulation results indicated that PAESO-modified asphalt models had reached the most stable configurations at a mixing temperature of 160 °C, as evidenced by fewer and more homogeneous distributed small bright spots observed in fluorescence images. This suggested that the outstanding compatibility between PAESO and asphalt binders could be obtained at the optimal mixing temperature of 160 °C. Furthermore, the rheological characteristics of asphalt binders modified with PAESO were examined through Dynamic Shear Rheometer and Bending Beam Rheometer tests. The results revealed that PAESO mainly exhibited a softening effect by significantly enhancing the flexibility, stress relaxation, fatigue, and thermal cracking resistance of the base asphalt binders at intermediate and low temperatures. PAESO-L modified asphalt manifested elastic properties akin to those observed in polymer-modified asphalt within the low-frequency and high-temperature domain. Additionally, PAESO derived from monomers with a higher functionality presented notable benefits in enhancing thermal and fatigue cracking resistance than that of PAESO with a lower functionality. These findings provide valuable insights for the preparation and development of bio-polymer additives for use in asphalt materials.

Characterization of viscoelastic behavior of basalt fiber asphalt mixtures based on discrete and continuous spectrum models.

In order to analyze the differences between the master curves of relaxation modulus E(t) and creep compliance J(t) obtained from discrete and continuous spectrum models, and to comprehensively evaluate the effect of basalt fiber content on the viscoelastic behavior of asphalt mixtures, complex modulus tests were conducted for asphalt mixtures with fiber content of 0%, 0.1%, 0.2% and 0.3%, respectively. Consequently, the master curves of Viscoelastic Parameters of asphalt mixtures were constructed according to the generalized Sigmoidal model(GSM) and the approximate Kramers-Kronig (K-K) relationship. Then, transformation of master curves using discrete and continuous spectrum models to obtain the models of E(t) and J(t) containing all viscoelastic information. Also, the accuracy of the models of E(t) and J(t) was evaluated. The results show that the addition of basalt fibers improves the strength, stress relaxation and deformation resistance of asphalt mixtures. It is worth noting that basalt fibers achieve the improvement of asphalt mixtures by changing their internal structure. Considering the different viscoelastic master curves at four dosages, the optimum fiber dosage was 0.2%. In addition, both discrete and continuous model conversion methods can obtain high accuracy conversion results.

AUSTRAL WRIGHT ALLOY B25 (UNS C17200)

Abstract Austral Wright Alloy B25 (UNS C17200) is a wrought beryllium copper alloy. It provides the highest strength of any copper alloy, with electrical conductivity considerably greater than that of other high-strength copper alloys. Since it is heat treated after forming, it provides excellent formability and ductility. This alloy features good stress relaxation resistance and high fatigue strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Cu-943. Producer or source: Austral Wright Metals.

Crystallography and diffraction patterns of the precipitates in Cu-3 wt% Ti alloy

Cu–Ti alloys are candidates for replacing Cu–Be alloys owing to their excellent mechanical properties, bending properties, and stress relaxation resistance. However, the precipitation behavior of Cu–Ti alloys remains poorly understood. In this study, diffraction patterns, orientations, and morphologies of continuous and discontinuous precipitates in a Cu–3 wt% Ti (Cu–3Ti) alloy are investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). In the peak-aging condition, numerous rod-like nanosized continuous precipitates (CP) of β′-Cu4Ti are uniformly distributed in the Cu–3Ti alloy. The CP retain their tetragonal structure, and their orientation relationships with the matrix are determined as [001]Cu//[001]β' and (010)Cu//(310)β', exhibiting six variants. With increasing aging time, discontinuous precipitates (DP) of β-Cu4Ti grow at the grain boundaries, displaying an orthorhombic structure (a = 0.453 nm, b = 0.4342 nm, and c = 1.293 nm). The orientation relationships between the DP and the Cu-matrix are determined as (Laughlin and Cahn, 1975; Han et al., 2016; Datta and Soffa, 1976; Han et al., 2020; Huang et al., 2023; Soffa and Laughlin, 2004; Wang et al., 2021; Si et al., 2016; Markandeya et al., 2004; Nagarjuna et al., 2001) [1-10]Cu//[501]β and (111)Cu//(010)β. Typical diffraction pattern models of the CP and DP in different directions were simulated, and the simulations were in good agreement with the experimental data.

Influence of trace silicon addition on the strengthening precipitates, mechanical properties and stress relaxation resistance of Cu-Cr alloy

First-principles calculations and experimental studies, including transmission electron microscopy (TEM), electrical conductivity measurements, and yield strength and stress relaxation resistance tests, were carried out to determine the influence mechanism of trace Si on the precipitates and stress relaxation resistance of a Cu-Cr alloy. TEM observation and aging precipitation kinetic analysis showed that the addition of trace Si significantly refined the Cr-rich precipitates of the Cu-Cr alloy but did not appreciably promote the nucleation of the precipitated phase. The influence of trace Si on the Cr-rich precipitates was assessed in terms of the Si-Cr and Si-vacancy interactions. The first-principles calculations reveal that there exists a strong attraction between Si and Cr with an interaction energy of − 0.27 eV for the nearest neighbor, which could promote the formation of Si-Cr clusters in the early aging stage that serve as heterogeneous nucleation particles for precipitates and induce the refinement of body-centered cubic (bcc) Cr-rich precipitates, resulting in an increase in the yield strength of the Cu-Cr alloy. The strengthening precipitates of the Cu-Cr-Si alloy mainly consisted of fcc Cr-rich precipitates and bcc Cr-rich precipitates, the strengthening mechanisms of which were the dislocation shear mechanism and dislocation bypass mechanism, respectively. In terms of performance, the conductivity of the Cu-Cr alloy decreased with the addition of trace Si from 94.5% IACS to 92.5% IACS, the yield strength increased from 178 MPa to 193 MPa, and the stress relaxation rate decreased from 18.93% to 15.27%. The improvement in the stress relaxation resistance of the Cu-Cr alloy with the addition of trace Si was mainly attributed to the drag effect of the element on dislocation movement and the refinement effect of the element on Cr-rich precipitates.

Effect of Co/P micro-alloying on stress relaxation behaviour of Cu-15Ni-8Sn alloy

To improve the stress relaxation resistance of the Cu-5Ni-S8n alloy, the effects of Co or P addition on its stress relaxation resistance were investigated by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction), X-ray diffraction, and high-temperature creep durability tester. The results revealed that the relaxation rate increased dramatically as the temperature rose. The thermal stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition; After 100 h of stress relaxation tests at 200°C or 250°C, the residual stress value of the Cu-15Ni-8Sn alloy increased by 23 MPa or 22 MPa with Co addition, which was associated with the consumption of vacancies by Co atoms and the pinning effect of Co atoms on dislocation. However, at 250°C, the stress relaxation resistance of the Cu-15Ni-8Sn-0.2P alloy was lower than that of the Cu-15Ni-8Sn alloy. This difference was due to the inclusion of P, which promoted the recrystallization reaction. Article highlights Recrystallization and the decrease of dislocation density are the major reasons for the stress relaxation of the samples. The stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition. The addition of the P element is not conducive to the improvement of thermal stress relaxation resistance.

Effect of σ-Phase on the Strength, Stress Relaxation Behavior, and Corrosion Resistance of an Ultrafine-Grained Austenitic Steel AISI 321

This paper reported the results of research into the effect of Equal Channel Angular Pressing (ECAP) temperature and 1-h annealing temperature on mechanical properties, stress-relaxation resistance, and corrosion resistance of austenitic steel AISI 321L with strongly elongated thin δ-ferrite particles in its microstructure. The formation of α′-martensite and fragmentation of austenite grains takes place during ECAP. Ultrafine-grained (UFG) steels demonstrate increased strength. However, we observed a reduced Hall–Petch coefficient as compared with coarse-grained (CG) steels due to the fragmentation of δ-ferrite particles. UFG steel specimens were found to have 2–3 times higher stress-relaxation resistance as compared with CG steels. For the first time, the high stress-relaxation resistance of UFG steels was shown to stem from a internal stress-relaxation mechanism, i.e., the interaction of lattice dislocations with non-equilibrium grain boundaries. Short-time 1-h annealing of UFG steel specimens at 600–800 °C was found to result in the nucleation of σ-phase nanoparticles. These nanoparticles affect the grain boundary migration, raise strength, and stress-relaxation resistance of steel but reduce the corrosion resistance of UFG steel. Lower corrosion resistance of UFG steel was shown to be related to the formation of α′-martensite during ECAP and the nucleation of σ-phase particles during annealing.

Combination of enhanced strength-ductility trade-off and stress relaxation resistance of MWCNTs reinforced Sn–5Sb-0.3Cu matrix composite

In this study, the strength-ductility trade-off and stress relaxation (SR) behavior of Sn–5Sb-0.3Cu (SSC503) alloy reinforced with (0, 0.05and 0.1 wt%) multi-walled carbon nanotubes (MWCNT) have been investigated under different pre-strains and initial stress levels. The results show that the pre-deformation can extend the duration of initial SR stage and significantly promote the stress reduction rate. The SSC503–0.05MWCNT composite alloy exhibits the optimum increase in SR resistance, yield strength (σy), ductility, and creep threshold stresses with the values of 75.8%, 17.3%, 77.9% and 10.6%, respectively. The scanning transmission electron microscopy (STEM) images and electron probe microanalyzer (EPMA) revealed that the distribution of MWCNT in SSC503 alloy was concentration dependent. 0.05MWCNT concentration induced a dendritic/cellular transition of β-Sn grains and restrained the growth of β-Sn, Cu6Sn5, SnSb, Sn3Sb2 and Cu2Sb IMC compositions, whereas 0.1MWCNT led to the partial agglomeration of MWCNT into β-Sn grain surfaces. MWCNTs are adsorbed at the surface-active atoms of Sb metalloid to form Sb-coated MWCNTs (Sb/C) in situ, which act as a bridge between MWCNT and Cu6Sn5 particles. The modified composites represent a vital technological progress for utilization in high temperature solder applications.

Distribution of the mechanical properties of Ti–Cu combinatorial thin film evaluated using nanoindentation experiments and molecular dynamics with a neural network potential

The combinatorial approach is a prominent method for synthesizing samples with composition gradients and that enables the high-throughput discovery of new materials. It enables high-throughput property screening to delineate the composition–structure–property relationship and identify atomic compositions with desired properties. Titanium–copper (Ti–Cu) alloy is widely used in electronic devices because of its excellent mechanical properties, such as stress relaxation resistance, bond formality, and workability. Synthesizing Ti–Cu thin film using the combinatorial approach could reveal a new application of the alloy. Aiming to discover a new application of the alloy, Ti-Cu thin film was synthesized using combinatorial approach. After synthesizing Ti-Cu thin film, we conducted XRD analysis of Ti-Cu thin film and then nanoindentation test. In addition to these experimental procedures, we have utilized reverse analysis method to obtain the mechanical properties of the thin film. We finally obtained the mapping of crystal structures and mechanical properties with respect to the atomic composition. To reveal the mechanical properties and their mechanisms, we employed molecular dynamics (MD) simulation as a tool to predict mechanical properties from the perspective of atomic simulation; however, it requires interatomic potentials to depict the movements of atoms. Because of the complex structure of Ti–Cu thin film synthesized using the combinatorial approach, the creation of interatomic potentials is a difficult and time-consuming process. Therefore, interatomic potentials were developed in this study using a neural network (NN), which enabled MD simulations of the Ti–Cu thin film, which is our particular interest. These were referred to as neural network potentials (NNPs). MD simulations were conducted with NNPs to study the mechanical properties of Ti–Cu thin film. First, ab initio molecular dynamics (AIMD) simulations were performed to obtain the relationships between the atomic coordinates and the corresponding total potential energies (as well as interatomic forces) of each atom. Subsequently, the relationship between the atomic coordinates and atomic energies were used as a training dataset for the NN, and a desirable NNP was developed by optimizing the parameters of the NN. The developed NNP was then tested to check its reliability and accuracy. It was found that the NNP could accurately predict the energies and forces calculated by the AIMD simulations. The mechanical properties of the Ti–Cu thin film were then computed using the NNP and MD simulations. Some material cases were verified with many-body interatomic potentials (e.g., modified embedded-atom method (MEAM) potential) and results obtained by experiments and ab initio calculations. Finally, using MD simulations with the developed NNP, we investigated the mechanism of the mechanical properties from the perspective of atomic scales. The mechanical properties and their distribution were examined via a comprehensive experiment and MD simulation approach. • This study reveals mechanical properties and their mechanisms of Ti-Cu thin film using nanoindentation experiments and Molecular Dynamics (MD) simulation. • Ti–Cu thin films with different composition ratios were created using a combinatorial synthesis approach. • The mechanical properties of the film and its distribution were measured using nanoindentation experiments. • Ab initio MD simulations were performed to create Neural Network potential (NNP). • MD simulation using a NNP was conducted to clarify the mechanical properties of the film.

Discontinuous precipitation in a Cu-10Ni-1Si alloy with ultra-high strength, high shock absorption, and good stress relaxation resistance

The discontinuous precipitation in a Cu-10Ni-1Si alloy aged at 500 °C and 550 °C was studied to clarify the types of discontinuous precipitates, and the crystal relationships between precipitates and the matrix. The continuous δ-Ni2Si precipitates were detected in the initial aging stage, then discontinuous β-Ni3Si and continuous δ-Ni2Si precipitates were detected simultaneously. The crystal relationship between discontinuous β-Ni3Si precipitates and the copper matrix at the beginning of aging was that: (1̅11̅)Cu//(111̅)β, [011]Cu//[011]β. The lamellar discontinuous β-Ni3Si precipitates significantly improve stress relaxation resistance and damping properties, which are attributed to the interaction between lamellar structure and dislocation motion. These findings indicated that the formation of the lamellar discontinuous precipitates tends to prevent dislocation slip and promote precipitation, resulting in enhanced mechanical properties and conductivity properties simultaneously.