Increase In Plastic Deformation Research Articles

The effect of secondary dendrite orientation on thickness debit effect of nickel-based single-crystal superalloy with tubular samples

Secondary dendrite orientation and wall thickness considerably affect the stress rupture life of thin-walled samples. However, the effect of the secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys has not been thoroughly investigated until now. Owing to geometrical constraints, typical sheet samples cannot reveal the mechanism responsible for the thickness debit effect in turbine blades. This study examined the effect of secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys at 1100°C/137 MPa in tubular samples. As the wall thickness decreased from 1.5 mm to 0.3 mm, the stress rupture life decreased from approximately 170 h to 64 h, demonstrating a noticeable thickness debit effect. Among the different secondary dendrite orientation areas, the variation in plastic deformation increased from 7% (1.5 mm) to 45% (0.5 mm) and subsequently decreased to 4% (0.3 mm). In thinner samples, the thickness contraction and microstructure evolution were more pronounced in the [100] areas than that in the [110] and [210] areas. The theoretical calculation quantitatively indicated that as the effective stress increased, the contribution of plastic deformation (45%) was slightly lower than that of oxidation (55%) in 0.3 mm samples; nevertheless, plastic deformation played a prominent role in 0.5, 0.8, 1, and 1.5 mm samples and increased from 61% (0.5 mm samples) to 85% (1.5 mm samples). In thinner samples, increased plastic deformation in the secondary dendrite orientation of the [100] areas and oxidation increased the effective stress, resulting in a shorter rupture life. These findings are conducive to the structural optimization and performance improvement of turbine blades.

Ballistic resistance of 7XXX laminate aluminum alloy plates and base alloys subjected to different projectiles

The ballistic impact of two 7XXX aluminum alloys, 7A52-T6 and 7A62-T6, as well as their combination in a 7B52 laminate plate, was simulated and experimentally tested. Three types of projectiles were utilized hard ogival nosed, hard blunt nosed, and 304 steel core projectiles to investigate the ballistic resistance and failure mechanisms of the aluminum alloy targets. Additionally, an existing modified Gurson-Tvergaard-Needleman (GTN) model incorporating shear, void growth, and spalling failure mechanisms, was employed to simulate the ballistic impact process, utilized to analyze energy dissipation during impact. The results reveal that the 7A52 alloy only experiences ductile hole expansion failure, whereas the 7A62 high-strength aluminum alloy undergoes spalling and fragmentation subsequent to penetration, leading to potential impact hazards. Due to its backing layer being the highly ductile 7A52 alloy, the laminate plate will not produce fragments after penetration. The improved GTN model provided better predictions of the impact failure modes of the aluminum alloys. Concerning impact performance, when subjected to hard ogival projectiles, the laminate alloy did not enhance material impact resistance. However, when impacted by blunt-nosed projectiles, the laminate alloy exhibited a 27 % improvement over the 7A52 plate and an 11.9 % increase over the 7A62 plate. Furthermore, when impacted by 304 steel core ogival projectiles, the laminate alloy demonstrated over a 41.3 % improvement compared to the 7A52 plate and over a 15.5 % increase compared to the 7A62 plate. The laminate plate's high ballistic performance was attributed to the increased plastic deformation energy after spalling failure, while ensuring high energy absorption during ductile hole expansion penetration.

Electrochemical and Mechanical Properties of Hexagonal Titanium Dioxide Nanotubes Formed by Sonoelectrochemical Anodization.

This study aimed to investigate the fabrication and characterization of hexagonal titanium dioxide nanotubes (hTNTs) compared to compact TiO2 layers, focusing on their structural, electrochemical, corrosion, and mechanical properties. The fabrication process involved the sonoelectrochemical anodization of titanium foil in various electrolytes to obtain titanium oxide layers with different morphologies. Scanning electron microscopy revealed the formation of well-ordered hexagonal TNTs with diagonals in the range of 30-95 nm and heights in the range of 3500-4000 nm (35,000-40,000 Å). The electrochemical measurements performed in 3.5% NaCl and Ringer's solution confirmed a more positive open-circuit potential, a lower impedance, a higher electrical conductivity, and a higher corrosion rate of hTNTs compared to the compact TiO2. The data revealed a major drop in the impedance modulus of hTNTs, with a diagonal of 46 ± 8 nm by 97% in 3.5% NaCl and 96% in Ringer's solution compared to the compact TiO2. Nanoindentation tests revealed that the mechanical properties of the hTNTs were influenced by their diagonal size, with decreasing hardness and Young's modulus observed with an increasing diagonal size of the hTNTs, accompanied by increased plastic deformation. Overall, these findings suggest that hTNTs exhibit promising structural and electrochemical properties, making them potential candidates for various applications, including biosensor platforms.

Dynamic behaviors of sandwich panels with 3D-printed gradient auxetic cores subjected to blast load

This study experimentally and numerically investigated the blast resistance of sandwich panels composed of steel face sheets and 3D-printed gradient auxetic chiral core. Five gradient strategies were utilized in the design of auxetic core, including uniform gradient, positive gradient, negative gradient, center positive gradient and center negative gradient. Varying blast loadings were applied by adjusting the masses of explosive charges. The deformation/failure modes of sandwich panels were obtained in the experiments, in terms of the face sheets and gradient auxetic core. The effects of impulse and gradient type of auxetic core on dynamic responses of specimens were examined. In addition, the numerical simulation was employed to clarify the deformation process of sandwich panel, and to analyze the deformation mode of auxetic cores under sufficient compression. It was shown that higher impulse was associated with increased plastic deformation in the face sheet and more serious shear and tensile tearing within the auxetic core. The auxetic cores of varying gradient types displayed distinct compress deformation behaviors. Among them, the negative gradient variant exhibited the least permanent deflection, and the superior negative Poisson's ratio effect, indicating enhanced blast resistance. This work not only contributes to a strategy for designing gradient auxetic cores with enhanced blast resistance, but also provides valuable insights into experimentally understanding the response of complex auxetic configurations under blast loads.

Enhanced steel machining performance using texture-controlled CVD alpha-alumina coatings: Fundamental degradation mechanisms

Cemented carbide inserts coated with CVD α-alumina, particularly those exhibiting a (0001) texture, have proven highly effective in steel turning. Despite the established superior performance of (0001) textured alumina coatings, the underlying reasons remain unclear. This study explores the influence of the crystallographic texture of alumina on wear mechanisms in various chip-tool contact zones on the insert rake face. The objective is to establish a fundamental understanding of the active degradation mechanisms and machining performance by relating coating texture to the orientation and deformation of individual Al2O3 grains. Two multilayered coatings, Al2O3 on Ti(C,N), featuring (0001)- and (112‾0)-textured CVD α-alumina, were assessed in dry turning of a bearing steel. The wear rate of the (112‾0) coating was double that of the (0001) coating. Worn coatings exhibit nano-terrace formation at the insert edge, likely due to chemical etching. In the sticking zone, plastic deformation leads to larger facets for grains oriented with the chip flow direction, while rounded surfaces result if this condition is not met. In the transition zone, both (0001) and (112‾0) textured coatings undergo increased plastic deformation accompanied by sub-surface dislocations. (0001) texture deforms more by basal slip creating a wavy coating pattern with steps present at larger misalignments of the lattice planes in neighboring grains while (112‾0) texture deforms by several slip systems creating elongated ridges and ruptured-like areas resulting in rougher surface. This difference in surface morphology is then inherited by the abrasion of submicron coating fragments embedded in the chip (more in (112‾0) texture) in the sliding zone resulting in an even rougher surface. Chemical reaction with the hot chip may also contribute to wear acting as an additional mechanism. This fundamental understanding contributes to the potential enhancement of steel machining using texture-controlled CVD alumina coatings, ultimately improving coated cutting tool performance.

The study investigates the effects of tool pin length, rotation speed, and dwell time on the microstructure and tensile strength of dissimilar joints between low-carbon galvanized steel and aluminium T6-6061 through friction stir spot welding

Friction stir welding is an efficient method for joining steel and aluminum plates at a point of disturbance. In many studies, the tool is only introduced into the aluminum plate, avoiding penetration into the steel plate due to its high strength and the need for a robust tool. Under such conditions, the created connection usually possesses low mechanical properties. In this research, by increasing the strength of the H13 steel tool through thermal operations, the possibility of penetration and bonding of aluminum 6061 with galvanized low-carbon steel has been provided. Moreover, by penetrating the steel plate, the integration of galvanized layers in the disturbance region has been facilitated. The examined variable parameters include pin length, rotational speed, and tool dwell time. Mechanical properties such as tensile strength, fracture force, and Vickers hardness were investigated. Furthermore, the weld microstructure and intermetallic layers were examined using scanning electron microscopy (SEM) and EDS analysis. Tensile and shear strength increase with an increase in pin length, rotational speed, and tool dwell time. Shear fracture loading showed a decrease with increasing pin length, then reached its maximum value when using long pins, while continuously increased with higher rotational speed and longer tool dwell time. As we approach the center of the weld in both the steel and aluminum parts, smaller grain sizes are observed due to increased plastic deformation, more material mixing, and increased mechanical tool pressure, while in the heat-affected zone, a coarse grain structure forms. Hardness in the aluminum plate decreased in the heat-affected zone and reached its minimum value in the thermo-mechanical-affected zone, then increased to the maximum value in the nugget zone, while hardness changes in the steel plate were uncertain. The most influential parameter on mechanical and microstructural properties was pin length, followed by rotational speed and tool dwell time.

Ultrahigh intermediate-temperature strength and good tensile plasticity in chemically complex intermetallic alloys via lamellar architectures

As a newly emerged class of materials, chemically complex intermetallic alloys (CCIMAs) with exceptional thermal and mechanical properties are a promising candidate for high-temperature structural use. However, serious intergranular embrittlement at intermediate temperatures (600∼800 °C) is frequently found in those CCIMAs, obstructing their large-scale engineering applications. In this study, through deliberately tailoring thermomechanical processing, we designed a lamellar-structured (LS) L12-type Co-Ni-Al-Ti-Ta-Nb-B-based CCIMA that effectively overcomes this critical issue. The LS-CCIMA exhibits an excellent yield strength (YS) of ∼1.0 GPa with a large tensile elongation of ∼17% at room temperature. More prominently, it also presents an anomalous YS of ∼1.2 GPa combined with an acceptable tensile elongation of ∼10% at intermediate temperatures ranging from 600 to 800 °C, outperforming those of many other simple ordered intermetallics and conventional superalloys. Such superb immediate-temperature strengths primarily originate from the high anti-phase boundary energy caused by the addition of multiple alloying elements (Ti, Ta, and Nb) and the pile-ups of geometrically necessary dislocations. Moreover, we attribute the acceptable tensile plasticity to the increased plastic deformation capacities from the activation of various deformation-induced substructures (e.g., dislocation pairs at 600 °C and superlattice intrinsic stacking faults at 800 °C) and the inhibiting mechanisms of the lamellar structures on oxygen-induced grain boundary damage and microcrack's propagation. This work provides a new pathway for the innovative design of strong-yet-ductile heat-resistant CCIMAs.

Low cycle fatigue behavior of additively manufactured Haynes 282: Effect of post-processing and test temperature

This study investigated the fully reversed (R = -1), strain-controlled low cycle fatigue behavior of laser powder bed fused Haynes 282 at temperatures ranging from −195 to 871 °C and at strain amplitudes of 0.010 and 0.005 mm/mm. By comparing the fatigue behaviors of hot isostatically pressed (HIP) specimens in machined surfaces (HIP/M) and the Non-HIP ones in un-machined surfaces (Non-HIP/UM), the combined effect of surface condition and hot isostatic pressing was analyzed and discussed. The Non-HIP/UM specimens showed shorter fatigue lives compared to HIP/M ones from −195 to 649 °C, which was attributed to the presence of surface micro-notches and volumetric defects. This difference attenuated above 649 °C due to the combined effects of increased plastic deformation, which mitigated the negative impact of surface anomalies, and oxidation, which accelerated crack initiation and growth. The tests at −195 °C tended to suppress cyclic plastic deformation, especially at the lower strain amplitude, which led to improved fatigue lives. Lastly, both HIP/M and Non-HIP/UM specimens exhibited similar stress responses with respect to test temperature; at 21, 204, 760, and 871 °C, cyclic softening occurred due to shearing of γ′ precipitates by persistent slip bands, while at other temperatures, the softening was balanced or overcome by cyclic hardening due to deformation twinning (i.e., at −195 °C) and dislocation multiplication during ordinary slip (i.e., at 427 and 649 °C).

Effect of strain rate on fractography texture descriptor of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y = 2–6%)composite after multiple ECAP passes: second order statistical texture analysis conjunction with regression analysis

The tensile strength of the ECAP processed composite of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y=2-6%) at various strain rates from 0.0001 to 1s-1 with an increment of 10 was examined in relation to the seven-fracture image texture descriptor through void features such as void size and distribution. In order to measure the matrices of voids on the fracture surface created through the coalescence of void results to enhance the material hardening as strain rate increases, the second order statistical texture analysis has been used. With respect to the rising strain rate, it was observed that the composite fracture image feature parameter correlation, homogeneity improved by 6 %, and 20.74% for AA6063/12%Si3N4/6%Cu(NO3)2 after I passes as compared to AA6063/12% Si3N4 after III pass. The contrast was reduced by around 58.643% when reinforcement went from a single reinforcement of 12% Si3N4 with I Pass to a composite of two reinforcements (Si3N4, Cu(NO3)2) that had 6% Cu(NO3)2 with I Pass. After three passes on AA6063/12%Si3N4/2%Cu(NO3)2, the maximum entropy was seen due to the material's increased plastic deformation, which led to an uneven particle distribution. As strain rate and copper nitrate percentage grew from 0 to 6 percent, the tensile strength of the composite improved by 34.69%. To assess the importance of fracture image features in relation to tensile strength with respect to strain rate, a regression model was developed. In order to get information about the fracture studies from fractography, the contrast with varying strain rate was nevertheless the aspect, which had the greatest influence.

Improving the Corrosion Resistance of TNTZ in Hanks’ Solution after Thermomechanical Treatment

Ti-29Nb-13Ta-4.6Zr (TNTZ) is a new titanium alloy potentially to be used as bone implant material because of its advantages in terms of strength, ductility, non-toxicity, corrosion resistance, and biocompatibility. Its mechanical properties are suitable for bone applications; however, there are still problems related to its corrosion behavior when used for a long time. Therefore, this research aims to determine the corrosion rate and types, and provide corrosion prevention by applying the thermomechanical treatment on TNTZ in Hanks’ solution. The limitation of this research was in not conducting the TNTZ biocompatibility tests. This research was conducted using the potentiodynamic polarization method in Hanks’ solution as the corrosive medium at a temperature of 37°C and a pH of 6.8. Before corrosion testing, a TNTZ sample was treated with thermomechanical treatment combined with solution treatment at a temperature of 850°C and a holding time of 45 minutes, followed by rapid cooling (water quenching), and plastic deformation with deformation variations of 10%, 15%, and 20%, and it was ended with aging heat treatment at a temperature of 300°C and holding time for 1 hour. The novelties of this research are the valid data of corrosion rate and type of TNTZ, which were unavailable before, and corrosion prevention through thermomechanical treatment of TNTZ in Hanks’ solution. The thermomechanical treatment is proved to reduce the pitting corrosion in TNTZ. The results show that thermomechanical treatment and increased plastic deformation can reduce the value of the corrosion rate, as evidenced by the pre-thermomechanical and thermomechanical TNTZ corrosion rates with deformation variations of 10%, 15%, and 20%, respectively, which were 5.522 x 10-4 mmpy; 2.754 x 10-4 mmpy; 2.290 x 10-4 mmpy; and 2.064 x 10-4 mmpy, respectively. TNTZ, after thermomechanical treatment, had the lowest corrosion rate, i.e., 2.064 x 10-4 mmpy, while Ti-6Al-7Nb had the highest one, i.e., 3.05 x10-2 mmpy. The type of TNTZ corrosion is pitting corrosion, as shown by the loss of zirconium that reduced the volume, causing pits to occur. Meanwhile, after thermomechanical treatment, pitting corrosion happened on TNTZ because of the loss or release of zirconium. This research shows that after thermomechanical treatment, TNTZ is the best material compared to other materials for biomedical applications based on corrosion resistance.

Wear Characteristics of Wire-Arc Additive Manufactured SS308L

Abstract Wire arc additive manufacturing (WAAM) is an efficient metal additive manufacturing technology. It can be easily accomplished with a gas metal arc welding (GMAW)—cold metal transfer (CMT) machine due to low heat input and low spatter generation characteristics. Austenitic stainless steel (ASS 308L) single thin walls were fabricated using ER308L filler wire having 1.2 mm diameter. The wear summary of the WAAM-processed 308L ASS under dry sliding at severe loading conditions is presented. Wear tests were done under dry (unlubricated) conditions, using a typical high-load pin-on-disc tribometer. AM-ASS processed with a lower heat input exhibited a low coefficient of friction (COF) and wear-rate. The microhardness is observed to be reducing steadily from the bottom layer to the top layer along the building direction to roughly 11.73%, 10.09%, and 8.44% in low, medium, and high heat input, respectively. This is attributed to the thermal history experienced by the material. X-ray diffraction (XRD) analysis of wear debris reveals that martensite is the most prevalent phase. In the wear behavior of AM-ASS, austenite transforms into martensite due to the metastability of ASS during plastic deformation. At severe stresses, plastic deformation of sliding surfaces is more prevalent. Ferrite (%) concentration decreases with the increasing load due to increased plastic deformation, which converts austenite to martensite. As deformation wear debris rolls, it hardens, fractures, and becomes cylindrical, which confirms the adhesive wear mechanism.

Alginate ester: New moisture-scavenging excipients for direct compressible pharmaceutical tableting

The objective of this work is to evaluate methyl ester alginates and alginic acid (AA) as moisture-scavenging excipients for the formulation of aspirin tablets obtained by direct compression. The tablets were stored at accelerated conditions (40 °C/75 % RH) and assessed for changes in tensile strength, mass, thickness and disintegration time. While moisture caused a reduction in the hardness of MCC and AA tablets, hardness of the tablets made from methylated materials was virtually unaffected. The physical stability of alginate ester tablets was found to be related to their increased plastic deformation leading to extended interparticle contact with less impact on tablet porosity. Finally, the combination of higher moisture affinity and lower water dissociation exhibited by alginates esters resulted in tablets with the lowest aspirin degradation. These findings suggest that excipients with high water retention can act as moisture-scavengers without losing their functional properties and reducing the degradation of moisture-sensitive drugs.

Strain rate dependence of tensile properties and strengthening mechanism of Ti6Al4V alloy undergoing different coverage layers of laser shock peening

Understanding the response of the Ti6Al4V alloy undergoing different coverage layers of laser shock peening (LSP) and the strain rate dependence of tensile properties is indispensable for its wide applications. Herein, the Ti6Al4V alloy specimens subjected to different coverage layers of LSP were employed in the uniaxial tensile testing with the strain rate of 0.001 s−1, 0.005 s−1, 0.01 s−1, and 0.02 s−1. The effects of the coverage layer on the tensile properties and its sensitivity to the strain rate were determined. The relationship between the microstructural morphologies, tensile behaviors, and strengthening mechanism were revealed. Moreover, the corresponding fracture behaviors of the tested specimens were summarized. It evidently shows that, the tensile properties and fracture behaviors of the Ti6Al4V alloy subjected to LSP treatment strongly depend on the strain rate. The ultimate tensile strength and the total elongation exhibit reverse trends with increasing strain rates and coverage layers, also, the typical ductile fracture pattern gradually evolves into the mixed ductility/cleavage fracture simultaneously. Upon the increasing plastic deformation process of LSP, the dislocation density, as well as the grain size are two intrinsic factors for controlling the strain hardening behavior and strain rate sensitivity, and the deformation twin provides another alternative factor.

Diffusivity of a point defect in the passive film on Ti with plastic deformation in 3.5% NaCl solution

The influence of plastic deformation on the diffusivity (D0) of the point defect in the passive film on Ti in 3.5% NaCl solution was investigated. Electrochemcial measurements including chronoamperometry measurement, electrochemical impedance spectroscopy and Mott-Schottky plots were performed, and the passive films were characterized by the Auger electron spectroscopy. The values of D0 were calculated based on the point defect model. The results shown that the passive film exhibited the n-type semiconductive property at different conditions. With the increased plastic deformation, the donor density and D0 increased, and the passive film became more defective. The relationship between D0 and stress corrosion cracking of Ti was discussed.

Improvement of the Corrosion Resistance and Potential for Metal Ion Release of Titanium Alloy Ti-6Al-4V ELI in Hanks Balanced Salt Solution (HBSS) after Thermomechanical

Ti-6Al-4V ELI is one of the titanium alloys commonly used as an implant material for its good biocompatibility. However, it has problems related to its corrosion behavior, especially when it is used for a long time. This study aimed to analyze the corrosion behavior of the implant material Ti-6Al-4V ELI in Hanks’ Balanced Salt Solution (HBSS) for a certain period, using the weight loss method in HBSS as the corrosive medium at 37°C. The immersion time was varied from two, four, until six weeks. Before immersion, the sample was thermomechanically treated with a combination of solution heat treatment at a temperature of 950°C and a holding time of 1 hour, water quenching, plastic deformation with deformation variations of 10%, 15%, and 20%, and, finally, aging heat treatment at a temperature of 550°C and holding time for 1.5 hours. The study results show that thermomechanical treatment and increased plastic deformation could reduce the corrosion rate and the metal ions released into the solution. These findings were evidenced by the corrosion rates of the pre-thermomechanical and the thermomechanical Ti-6Al-4V ELI with deformations of 10%, 15%, and 20% at the 6-week immersion of 6.57 x 10-6 mmpy, 4.27 x 10-6 mmpy, 3.89 x 10-6 mmpy, and 2.76 x 10-6 mmpy, respectively, and the metal ions released of 7.3 μg/L, 7 μg/L, 6.3 μg/L, and 6 μg/L, respectively. The corrosion rate of Ti-6Al-4V ELI under thermomechanical treatment, namely 2.76 x 10-6 mmpy, was the lowest compared to other materials in HBSS, while the highest one was that of Ti-6Al-7Nb of 3.05 x10-2 mmpy. In addition, the study results show that Ti-6Al-4V ELI under thermomechanical treatment is the best material compared to others for biomedical applications, based on corrosion resistance and metal ions released into HBSS.

Effects of Boriding, Nitrocarburizing, Nitriding and Post-oxidation Treatments on The Tribological Properties of DIN 32CrMoV12-10 Steel

In this study, the effect of different surface treatments was investigated to improve the friction and wear properties of DIN 32CrMoV12-10 steel. For this purpose, chrome plating, boriding, nitrocarburizing+oxidation, nitriding+oxidation processes were applied to the samples prepared from DIN 32CrMoV12-10 steel. After the procedures, the structural, morphological and mechanical properties of the samples were determined by XRD, SEM, hardness measurement device and profilometer. In order to determine the tribological properties of the samples, pin-on-flat wear tests were carried out. It was observed that a chromium layer was formed on the surface of the material after chrome plating. In boronized samples, it was observed that a boron layer was formed on the surface of the material and a diffusion layer was formed below it. The formed layers contain Fe2B and FeB phases. In nitrocarburized+oxidized and nitrided+oxidized samples, it was observed that the oxide layer on the material surface, a white layer just below it and a diffusion zone extending to the inner parts of the material were formed. The oxide layer formed on the surface consists of Fe2O3 and Fe3O4 phases, while the white layer and diffusion layers consist of ε-Fe2-3N and γ'-Fe4N phases. Due to the increased plastic deformation resistance with oxide layers, hard nitride phases and diffusion layers, the highest wear resistance was obtained from nitrocarburized+oxidized and nitrided+oxidized samples.

Mathematical modeling of planar physically nonlinear inhomogeneous plates with rectangular cuts in the three-dimensional formulation

Mathematical models of planar physically nonlinear inhomogeneous plates with rectangular cuts are constructed based on the three-dimensional (3D) theory of elasticity, the Mises plasticity criterion, and Birger’s method of variable parameters. The theory is developed for arbitrary deformation diagrams, boundary conditions, transverse loads, and material inhomogeneities. Additionally, inhomogeneities in the form of holes of any size and shape are considered. The finite element method is employed to solve the problem, and the convergence of this method is examined. Finally, based on numerical experiments, the influence of various inhomogeneities in the plates on their stress–strain states under the action of static mechanical loads is presented and discussed. Results show that these imbalances existing with the plate’s structure lead to increased plastic deformation.

Influence of plastic deformation on the corrosion behavior of CrCoFeMnNi high entropy alloy

In this research, the influence of plastic deformation on the corrosion behaviors of CrCoFeMnNi high entropy alloy were comprehensively investigated. As the degree of plastic deformation increases, both the acceptor density of the passive film and the thickness of the space charge layer increase, while the resistance of the passive film gradually weakens. The Fe and Cr oxides on the passive films decrease with the increasing plastic deformation degree, resulting in the weaker resistance of the passive film. Numerous dislocations formed after plastic deformation promote the increase of electrochemical dynamics and galvanic corrosion rate. Therefore, severe plastic deformation lowers the corrosion resistance of the alloy.

Investigation of the adhesive contact between a diamond indenter and single-Crystal copper substrate at low temperatures

ABSTRACT Considering the elastoplastic deformation of a single-crystal copper substrate, based on the atomic scale, a mixed potential function (EAM and Morse) and the Verlet algorithm were used to simulate the adhesion contact and separation process between a hemispherical diamond indenter and a single-crystal copper substrate at low temperatures. The influences of the temperature on the micro/nanomechanical properties of the material surface and on the mechanism of the subsurface deformation process were analysed. The results show that as the simulated temperature decreases, the time for adhesion to occur is delayed, and the adhesion forces increase slightly. While the indenter is being pressed, the temperature affects the generation and interaction of the dislocations in the substrate. As the temperature decreases, a large number of dislocations in the substrate are generated and then relatively reduced, and the load on the indenter fluctuates. A calculation of the mechanical properties of the material found that the contact stiffness was related to the elastic recovery energy. A smaller elastic recovery energy leads to a greater contact stiffness; thus, the indentation hardness is related to the plastic deformation energy. An increased plastic deformation energy results in a decreased indentation hardness.

Effect of Temperature and Moisture on the Impact Behaviour of Adhesive Joints for the Automotive Industry

This study focuses on evaluating the impact of aluminum adhesive joints as a function of temperature and moisture, in an effort to understand how these conditions affect their mechanical properties and behavior. After preparing the required specimens (using two different adhesives and adherend thicknesses), several tests have been made in order to determine these properties and compare their values to the predictions made using analytical methods. These tests were repeated with several distinct combinations of temperatures and moisture levels so that the effect of these properties can be properly interpreted. It was observed that higher temperatures strongly increase the ductility of the adhesive but mixed with moisture this can degrade them. Moisture can increase the energy absorbed through increased plastic deformation of the adhesive and improve behaviour at low temperatures.