Interface Of Dissimilar Materials Research Articles

Generation and propagation mechanism of cracks in welded joints of thin-walled capsules during hot isostatic pressing

The quality of the capsule has an important effect on the quality of hot isostatic pressing (HIP) products. The reliability of the capsule is a key factor in determining the success or failure of HIP. The capsule is mainly formed through a sheet welding process. In order to ensure the reliability of the weld in HIP, stainless steel with better high-temperature and high-pressure performance than Q235 steel needs to be used. In this case, the fusion line becomes a dissimilar-material interface, which is more prone to fusion-line failure. This paper focuses on examining and studying the formation mechanism of fusion line cracks in welded joints during HIP. The results show that, first, the increase of the HIP temperature weakens the strength near the fusion line significantly. Second, the higher the HIP temperature, the more severe the grain coarsening, and the grain size along the radial direction of the capsule exhibits a monotonic change. Third, since the HIP process changes the micro-zone grain orientation of mild steel, the distribution characteristics of ferrite and pearlite change as well. when the temperature and pressure are higher, the texture still exhibits a strong and complex distribution.

Tri-system integration in metal-oxide nanocomposites via in-situ solution-processed method for ultrathin flexible transparent electrodes

For stable operation of ultrathin flexible transparent electrodes (uFTEs), it is critical to implement effective risk management during concurrent multi-loading operation of electrical bias and mechanical folding cycles in high-humidity environments. Despite extensive efforts in preparing solution-processed uFTEs with cost-effective and high-throughput means, achieving in-situ nano-adhesion in heterogeneous metal-oxide nanocomposites remains challenging. In this work, we observed by serendipity liquid-like behaviour of transparent metal-oxide-semiconductor zinc oxide nanoparticles (ZnONPs) onto silver nanowires (AgNWs) developed by in-situ solution processed method (iSPM). This enabled us to address the long-standing issue of vulnerability in the nanocomposite caused by the interface of dissimilar materials between AgNWs and ZnONPs, resulting in a remarkably improved multi-loading operation. Importantly, substrate-integrated uFTEs constituted of the metal-oxide nanocomposite electrode semi-embedded in the polymer matrix of greatly thin <0.5 μm thickness is successfully demonstrated with the smooth surface topography, promoted by the tri-system integration including (i) AgNW-AgNW, (ii) ZnONP-ZnONP, and (iii) AgNW-ZnONP systems. Our finding unveils the complex interfacial dynamics associated with the heterogeneous interface system between AgNWs and ZnONPs and holds great promise in understanding the in-situ nano-adhesion process and increasing the design flexibility of next generation solution-processed uFTEs.

Investigation of identification method of crack tip location for obtaining fracture toughness of dissimilar material interface using displacement data by DIC

Investigation of identification method of crack tip location for obtaining fracture toughness of dissimilar material interface using displacement data by DIC

Modeling of temperature- and strain-driven intermetallic compound evolution in an Al–Mg system via a multiphase-field approach with application to refill friction stir spot welding

The prospect of joining dissimilar materials via solid-state processes presents an opportunity to obtain multi-material structures having a synergy of desirable properties of the joined materials. However, the issue of the formation of intermetallic compounds at the weld interface of dissimilar materials arises with that, depending upon the temperature and pressure conditions as per phase diagram. As the thickness of the intermetallic compounds may determine the mechanical properties of the joint, understanding the driving mechanisms and evolution of these intermetallic compounds in solid-state joining processes, such as refill friction stir spot welding (refill FSSW), is crucial. In this contribution, we account for the effect of different driving forces in a multiphase-field approach and investigate the evolution of the intermetallic compounds driven by chemical and mechanical forces. A finite-element simulation of the refill FSSW is pursued to obtain the peak temperature and strain at different locations of the weld interface. The microstructure simulations obtained via the multiphase-field model give insight into the morphology and kinetics evolution of the intermetallic compounds for both, the absence of strain (purely chemically-driven model) as well as presence of strain (chemo-mechanically-driven model). The consideration of strain proves to result in thicker intermetallic compound layer. Furthermore, the impact of interface energy and initial grain configuration is found to be significant on the overall intermetallic compounds evolution.

Analysis of local characteristics and microstructure of dissimilar metal interface in scrubbing refill friction stir spot welding joint

Friction stir spot welding (FSSW) is one of the solid-state welding methods and dissimilar material joining by FSSW has been investigated. ‘Scrubbing refill FSSW (Sc-RFSSW)’ has developed as a new dissimilar material joining method, and it was shown that Sc-RFSSW provides higher joint strength than conventional FSSW methods in joining the aluminum alloy and non-coated steel. In this study, the microscale testing was performed to evaluate the dissimilar material interfacial strength of Sc-RFSSW joints. The relationship between the interfacial strength distribution and the macroscopic strength of the Sc-RFSSW joint was analyzed. In addition, the microstructure of the dissimilar material interface was observed, and the relationship between the microstructure and the interface strength was shown.

Peridynamic analysis of materials interface fracture with thermal effect

A thermomechanical peridynamic framework is established for fracture analysis of dissimilar material interface coupled with residual thermal effect. In this frame, an extended peridynamic mixed-mode failure model considering thermal effect is proposed for interfacial fracture prediction, and the peridynamics-based methods for interface crack energy release rate and mode mixity computations are given. Meanwhile, a new peridynamic contact model is proposed for frictional contact modeling of crack surfaces. Then, three examples of the single edge-notched bimaterial (SENB), asymmetric bimaterial cantilever beams (ABCB) and four-point shearing (FPS) tests, are analyzed for the model verification and application. The elastic and interfacial fracture behaviors of these tests are predicted by the proposed peridynamic models, and compared to the analytical and the FEM solutions. The results show that the proposed peridynamic models can successfully predict the failure characteristics of materials interface, and capture the role of residual thermal effect on the interfacial fracture.

Ultrasonic elastography for nondestructive evaluation of dissimilar material joints

Dissimilar material joints or multilayered metals have become inevitable in the manufacturing industry due to the increasing demand for multifunctional materials with variable mechanical, thermal, or electrical characteristics in a single assembly. Lattice mismatch of materials at the interface of dissimilar materials leads to inferior mechanical characteristics. In particular, the mismatch in elastic properties indicated by a large initial elastic deformation is critical to determine the extent of variation in stress. However, nanoindentation, the most common and accepted technique to measure elastic modulus, is destructive, time-consuming, and can only examine mechanical properties within a limited area. A non-invasive elastographic mapping technique evaluates the mechanical properties using ultrasonic elastography to study incompressibility. The dissimilar joint between steel and copper was obtained via friction stir welding. The variation of the stress developed at the welded joint of the two different metals was evaluated from the dynamic bulk modulus map. A tensile test of the involved workpiece confirmed a good agreement with our analysis based on the dynamic bulk modulus elastographic mapping results. This study provides a rapid and non-invasive technique for the bulk metallurgic elastic modulus inspection to overcome the limitations of conventional methods.

Influencing mechanism of inherent aluminum oxide film on coach peel performance of baked Al-Steel RSW

A traditional resistance spot weld process in combination with Multi-Ring Domed welding electrodes was applied to join AA5754-O to low carbon steel. The coach peel performance of welds was compared between the as-welded (unbaked) and post-paint bake condition (baked). The unbaked joints exhibited button pullout fracture mode, whereas the baked joints were severely weakened and demonstrated an interfacial fracture mode which is attributed to the baking process inducing thermal stress at the dissimilar material interface which cracked the semi-continuous oxide film inclusions at the edge of the solidified aluminum nugget to form a more continuous defect layer across the diameter of the aluminum nugget. These defects act as low energy crack paths under applied loads and reduce joint strength by promoting undesirable interfacial fracture in baked welds.

On the Stress State of a Heterogeneous Plate Made of a Material with a Step Change in Elastic Characteristics in the Presence of an Inclusion System and Temperature Influence

In the formulation of thermoelasticity and in the framework of the conventional theory of thermal stresses, the problem on the stress state of an elastic piecewise-homogeneous plane or an infinite plate at non-uniform steady-state heating is considered. On the interface of dissimilar materials, the compound plane is reinforced by a collinear system of absolutely rigid thin inclusions and is subjected to mechanical and thermal influences. First, to determine the temperature distribution in a piecewise-homogeneous plane the corresponding boundary value problem of the theory of steady-state heat conduction is solved using the integral Fourier transform. Solving this problem is reduced to solving a singular integral equation (SIE) that allows an exact solution. Further, the elastic displacements of points of the compound plane, caused by mechanical and temperature influence, are determined by the known methods of thermoselasticity. Based on these results, solving the problem of the contact interaction between the system of inclusions and a compound plane is again reduced to solving SIE, which also allows an exact solution. A special case is considered.

Numerical simulation and experimental validation of joint performance in aluminum-steel lap welds formed by friction stir dovetailing

Abstract Friction stir dovetailing (FSD) is a new dissimilar material joining process that simultaneously forms a mechanical interlock and metallurgical bond at the dissimilar material interface. This work presents development of a modeling and simulation approach to predict mechanical performance of FSD thick section aluminum to steel joints. A finite element analysis (FEA) was carried out in order to predict the load-carrying capacity and failure location for aluminum thicknesses between 12.7 mm and 50.8 mm with different numbers of dovetails. The numerical results and corresponding experimental investigation are in agreement and suggest that the developed methods can be used effectively for design and analysis of FSD joints using standard FEA tools.

On the Feasibility of Tailoring Copper–Nickel Functionally Graded Materials Fabricated through Laser Metal Deposition

In this study, pulse-width modulation of laser power was identified as a feasible means for varying the chemical gradient in copper–nickel-graded materials. Graded material deposits of 70 wt. %. copper-30 wt. %. nickel on 100 wt. %. nickel and vice versa were deposited and characterized. The 70/30 copper–nickel weight ratio in the feedstock powder was achieved through blending elemental copper and 96 wt. %. Ni–Delero-22 alloy. At the dissimilar material interface over the course of four layers, the duty cycle of power was ramped down from a high value to optimized deposition conditions. This change was theorized to influence the remelting and deposition height, and by extension, vary the chemistry gradient. X-ray Energy Dispersive Spectroscopy (EDS) analysis showed significant differences in the span and nature of chemistry gradient with varying duty cycles. These observations were also supported by the variation in microhardness values across the interface. The influence of different chemistry gradients on the tensile performance was observed through mini-tensile testing, coupled with Digital Image Correlation (DIC). The strain fields from the DIC analysis showed variations in strain for different chemistry gradients. The strength measurements from these specimens were also different for different chemistry gradients. The site of failure was observed to always occur within the copper-rich region.

Adhesive strength and delamination behavior on micro textured dissimilar material interface

Adhesive strength and delamination behavior on micro textured dissimilar material interface

Emerging solar cells energy trade-off: Interface engineering materials impact on stability and efficiency progress

Emerging solar cell (ESC) carrier's dynamic transfer difficulties and instability at dissimilar material's interface seems to be potential distress. Electrical permittivity influences on photo carrier dynamics of nonpolarized organic and polarized organic-inorganic perovskite solar cell. ESC electrical efficiency and stability are consider to be managed broadly by carrier accumulation, extraction, and conduction techniques. Active materials optoelectric interaction and carrier accumulation are petite known. Its energetic dealings with dissimilar interface materials how support to faster carrier extraction and conduction are still in haze. In this drill, focus on active to interface materials key properties are imperative to find a way to promote electrical energy conversion and its steadiness. Selected advanced interface engineering materials (IEMs) architectures, conduction, and multifarious relations to active materials for efficient energy transfer ability and stability are reported precisely by the model. The interface structure consistency supports to systematize energy transfer, otherwise, disorder or energy loss is anticipated. Therefore, active material linkage to IEM photophysical, quantum, and choice of materials technologies are focused comprehensively to explore the pathway of ESC stability and efficiency progression.

Control of fracture at the interface of dissimilar materials using randomly oriented inclusions and networks

Fracture at or near the interface between two isotropic materials has been a subject of extensive research relevant to the problems encountered in aerospace, naval, electronic packaging, biomechanical engineering and other applications. The problems of edge cracks, semi-infinite interface cracks and substrate cracks under a thermally stressed film considered in the paper are representative of such analyses. We consider a possible improvement in the fracture resistance achieved by embedding randomly distributed stiff inclusions such as fibers, nanotubes, fiber or nanotube networks and ellipsoidal or spherical particles in the more compliant material. This results in a smaller mismatch between the stiffness of the joined materials that may prevent or alleviate fracture. Numerical examples demonstrate both the benefits and the limitations of enhancing the stiffness of the compliant material. In particular, the examples refer to the boundary between singular and non-singular interfacial edge stresses attempting to avoid the stress singularity by embedding random carbon nanotubes or networks. In the semi-infinite interfacial crack problem it is demonstrated that a small reduction in the stiffness mismatch of two materials at the interface causes a significant decrease in the strain energy release rate. The approach to the analysis of substrate cracks under a thermally stressed film is outlined accounting for the history of thermal loading and the effect of temperature on the properties of the film, substrate and embedded inclusions. The solutions presented in the paper rely on effective properties of randomly reinforced materials. The limitations of such approach in fracture problems and an estimate of its validity based on a comparison of scales at the tip of the crack and in the representative volume cell are discussed. It is suggested that fracture involving nanoparticle and nanotube reinforced materials can be characterized using effective properties.

Evaluation of stress field along dissimilar material interface with misfit dislocation in nano-scale

Evaluation of stress field along dissimilar material interface with misfit dislocation in nano-scale

A case study of thin film stress evolution at a dissimilar material interface via molecular dynamics simulations

Evolution of deformation and stress in growing thin films has been studied in this work using computational simulations that resolve matter at atomic length and time scales. For the surface layers of films laying on the substrate of a dissimilar material, the stress distribution analysis around defects becomes more challenging. Herein, spatial and temporal distribution of deformation and associated stress evolution are presented for different thin film formation events including (1) sub-monolayer growth during an early film nucleation stage and (2) coalescence of adjacent monolayer “islands.” Validity of the stress computed via local computations of the virial expression for stress in a system of interacting particles was checked by comparing to results obtained from considerations of local atomic deformation in conjunction with existing expressions for epitaxial thin film growth stress. For the geometries studied here, where a monolayer of film with a highly characterized linear defect, as in the case of a stacking fault, was simulated for coalescence, fairly good agreement was found. This result demonstrates that, for similar defects at the surface layer, with sufficient sub-ensemble averaging of the standard virial expression for stress, semiquantitative spatial stress distribution information can be obtained from atomic scale simulations. Using our validated stress computation method, we reveal significant stress localization during thin film growth processes, leading to pronounced differences in maximum and minimum stress observed over very small spatial extent (of order multiple GPa over 3–6 nm distances). One prominent mechanism of stress localization revealed here is coalescence between adjacent growing islands. For geometries explored here, stress manifesting during coalescence is highly localized.

Thermal-mechanical modeling on friction stir spot welding of dissimilar materials based on Coupled Eulerian-Lagrangian approach

A model of friction stir spot welding (FSSW) between aluminum alloy 6061-T6 and TRIP 780 steel is developed in this work based on the Coupled Eulerian-Lagrangian (CEL) method, which considers the material flow at the dissimilar material interface and also the interaction between the welding tool and workpiece. The cross-sectional view from the numerical result agrees well with the experimental observations. The material distribution at different plunge depths calculated by the model illustrates the formation of the hook during the welding process. The force and thermal history generated by the numerical work also correspond well with the experimental data. A force history generated through a tool with a smaller shoulder diameter is studied to further validate the model. The developed model can be useful for better understanding the effect of the welding tool on FSSW and optimization of the tool geometry.

Bonding of lithium niobate to silicon in ambient air using laser irradiation

In this paper, we introduce a bonding method in ambient air using laser irradiation to the face-to-face interface of dissimilar materials. This method is performed while keeping whole wafers of the materials at room temperature. We demonstrate the bonding of LiNbO3 to Si using pulsed nanosecond green laser irradiation. Laser use can minimize thermal stress owing to a large thermal expansion mismatch. The bonding characteristic obtained by an irradiation laser up to 2.5 J/cm2 in fluence is investigated. It is found that a LiNbO3 chip is strongly bonded to a Si chip by setting the laser fluence at the optimum range. A bond strength of over 2 MPa, which may be enough for the device applications, can be obtained.

ChemInform Abstract: Interfacial Magnetism in Complex Oxide Heterostructures Probed by Neutrons and X‐Rays

AbstractReview: 117 refs.

A geometrical approach to remove stress singularities in continuum models of multi‐material structures

AbstractIn the frame of stress based topology optimisation multi‐material structures are investigated. At the interface of dissimilar materials an adhesive joint shall be considered. Selecting a continuum approach to model the two adherends and the adhesive, stress singularities occur at the material‐interfaces due to the difference in the impedance [1].This contribution investigates a geometrical opportunity to remove singularities at the interface of two different linear elastic structures. Sensitivities of important parameters are qualitatively shown by a simple example consisting of two cubes under tension. (© 2015 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)