Subsequent Mechanical Properties Research Articles

Gradually Self-Strengthen DNA Supramolecular Hydrogels.

The dynamic mechanical strength of the extracellular matrix (ECM) has been demonstrated to play important role in determining the cell behavior. Growing evidences suggest that the gradual stiffening process of the matrix is particularly decisive during tissue development and wound healing. Herein, a novel strategy to prepare hydrogels with gradually enhanced mechanical strength is provided. Such hydrogels could maintain the dynamic properties at their initial states, such as self-healing and shear-thinning properties. With subsequent slow covalent crosslinking, the stability and mechanical properties would be gradually improved. This method is useful for sequence programmability and oxidation strategies, which has provided an alternated tool to study cell behavior during dynamic increase in mechanical strength of ECM.

Thermomechanical performance and multiscale modeling of hexagonal boron nitride modified out-of-autoclave manufactured silica fiber reinforced phenolic composites

In this study, high loadings of boron nitride (BN) nanoplatelets were added to silica fiber-reinforced phenolic composites to study the multifunctional impact of BN loading and manufacturing processing on the subsequent mechanical, thermal, and thermomechanical properties. A series of high-quality laminates were made with various loadings of BN using compression-molded out-of-autoclave processing. Three-point bend and short beam shear testing determined the relationship between BN loading and mechanical performance. The fracture properties were analyzed using optical and scanning electron microscopy. The thermal conductivity performance was increased up to a 93% improvement, indicating the thermal management multifunctionality of the modified composites without changing the crosslinking ability or glass transition temperature significantly. The modified performance of hybrid silica/phenolic/BN composites is demonstrated through micromechanical multiscale modeling, where BN loading and particle stress concentrations impact the modulus and strength of the composite.

Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness

Hot-work tool steels play a crucial role in applications exposed to extreme thermal, mechanical, and chemical stresses and require exceptional properties such as high strength, hardness, wear resistance, and toughness. The latter is crucial to prevent an unexpected tool failure due to the formation and propagation of fatigue cracks in demanding environments. In addition, high thermal conductivity is crucial to prevent overheating of the tool and the resulting degradation of the material. This study focuses on a new generation hot-work tool steel with increased Mo and W contents, which has excellent thermal conductivity but limited toughness, as it contains stable Mo-W carbides that remain stable up to 1100 °C. To improve toughness, an alternative heat-treatment method involving austempering at different temperatures was applied. The investigation begins with the characterisation of the chemical composition of the steel, followed by the determination of the martensite-start (MS) and martensite-finish (Mf) temperatures. Based on the results, the researchers established a set of samples for austempering heat treatment. They investigated the effects of different isothermal holding temperatures on the microstructure of the steel and its subsequent mechanical properties. The results show that reduced bainite formation, achieved by austempering at certain temperatures, led to significantly improved impact toughness and moderate hardness. This study also showed a correlation between the isothermal holding temperature and the extent of martensitic transformation, which affected the microstructure and mechanical properties of the steel.

Dislocation breakaway from nanoparticle array linear complexions: Plasticity mechanisms and strength scaling laws

Linear complexions are stable defect states, where the stress field associated with a dislocation induces a local phase transformation that remains restricted to nanoscale dimensions. As these complexions are born at the defects which control plasticity in metals, it is crucial to understand their impact on subsequent mechanical properties. In this work, atomistic modeling is used to understand how dislocation mechanics are altered by the presence of nanoparticle array linear complexions in a Ni-Al alloy. Molecular dynamics simulations are used to identify the critical shear stress needed to drive dislocation breakaway, first for nanoparticle arrays formed by Monte Carlo/molecular dynamics methods to represent realistic configurations and subsequently for simplified models that allow the effects of particle spacing and size to be varied in a controlled manner. A combined bowing and progressive unpinning mechanism is uncovered, leading to the demonstration of a new strength scaling law that differs in keys ways from classical Orowan bowing.

Synthesis of 2,5‐Diphenyl‐2H‐[1,2,3]triazole‐4‐carboxylic Acid Appended Phenylalanine for Thixotropic Metallogelation and Stiffness Manipulation

AbstractOrganic‐inorganic hybrid materials are highly important for designing and engineering bioinspired structures and functions. Herein, we have demonstrated the synthesis and metallogelation of triazole‐appended phenylalanine and resulting stiffness enhancement. The 2,5‐diphenyl‐2H‐[1,2,3]triazole‐4‐carboxylic acid was synthesized by sequential C−N bond formation and electro‐oxidative N−N coupling under metal‐free conditions and coupled with L‐Phe to develop the gelator. Starting with basic (pH 11) solutions (5 mg/mL) of gelator, we show that significant stiffness enhancement is achieved upon adding Ca2+. From rheology, the storage modulus exhibits 8‐fold increase by the calcium‐induced gelation. The calcium‐induced gels are thixotropic in nature. The calcium ion bivalency leads to “cross‐links” and promote assembly of gelators, which not only influences the gel microstructure but also manipulates subsequent mechanical properties of the metallogels.

Moisture Absorption Characteristics and Subsequent Mechanical Property Loss of Enset–PLA Composites

One of the drawbacks of natural fibers and their composites is their inherent hydrophilic nature. The effect of moisture on the mechanical properties of composites is irrefutable. This study deals with the hygroscopic characteristics of enset–PLA composites and their effect on the mechanical properties of the composites. To do this, injection-molded composite specimens with different fiber volume fractions, plasticizer ratios, fiber lengths, and fiber ages were considered. The specimens were exposed to distilled water, and the moisture absorption was monitored on a daily basis. Subsequently, the specimens were subjected to mechanical loading to determine the effect of moisture on their strength, stiffness, and strain at break strength. Lastly, the individual and joint effects of the considered factors were scrutinized using an optimal experimental design. The results of the study show that the maximum and minimum moisture uptakes were recorded for 25% and 15% fiber ratios, respectively. Due to the effect of moisture, the tensile and bending strength decreased by 11% and 5%, respectively, for the 15% fiber volume fraction and decreased by 16% and 13%, respectively, for the 25% fiber volume fraction. Increasing the amount of plasticizer increases the moisture resistance. The results indicate that Enset–PLA composites have competitive properties and stability when exposed to moisture.

Dependence of lithium‐ion battery separator porous structure and performance on synchronous bidirectional drawing process regulation of β‐crystal polypropylene

AbstractUneven separator porous construction inevitably raises lithium‐ion migration barriers within the separator and thus limits overall lithium‐ion battery (LIB) performance. In this research, serial LIB separators with various porous constructions were prepared precisely by adjusting the synchronous bidirectional drawing temperatures to confirm the bidirectional drawing mode‐determined porous constructions and subsequent mechanical properties, thermal stability and electrochemical properties of separators. Crystal structure analyses, porous construction diagnoses, mechanical property characterizations and electrochemical tests reveal the competitive relationship between lamella slip and separation during the synchronous bidirectional drawing process. Lamella slip weakens at lower drawing temperatures, enhancing lamella separation and molecular chain rupture within amorphous regions. Therefore, a separator with broken fibrils presents optimized permeability and smoothed ion migration channels, but inferior mechanical properties and thermal stability. Excessive temperature highlights lamella slip, which damages the pore‐forming process, worsens separator permeability and increases ion migration resistance. An appropriate drawing temperature of 100 °C maximally balances lamella slip and separation behaviors, retains intact fibrils and homogenized porous construction, which endows the separator with strengthened mechanical properties, isotropic thermal stability and optimized electrochemical performances. This study provides new insights for synchronous bidirectional drawing in practical separator fabrication and clarifies separator structure‐determined LIB performances. © 2023 Society of Industrial Chemistry.

Synergetic effect of milling speed and duration on particle morphology and mechanical properties of nanocrystalline Al matrix containing SiC

ABSTRACT In the present study, the composite sheets were produced by powder rolling the ball-milled Al/SiC mixture. The effect of milling speed (350–550 rev min–1) and milling duration (8 and 12 h) on the Al particle morphology and subsequent mechanical properties were examined for composites with different volume fractions of SiC. From the microstructural investigation, SiC particles are evenly distributed and well dispersed in the Al matrix; those are prepared under higher milling speed (550 rev min–1) and higher milling time (12 h). Furthermore, the flattened-shaped particle morphology was obtained under lower milling conditions, whereas the reduced-granule shape was obtained under higher milling conditions (550 rev min–1, 12 h). Consequently, the Al/SiC composite sheets made from a granule-shaped Al/SiC mixture show higher density, microhardness, and tensile strength due to significant consolidation and SiC uniformity. In addition, the tensile strength of 430.26 MPa has been achieved for the Al/2vol.-%SiC sheet compared to pure Al (393.49 MPa) under similar processing conditions.

Study on Macromorphology and Microstructure of Laser Cladding NiCrBSi Alloy Cladding Layer

Laser cladding technology is an advanced surface modification technology that can achieve the coating, repair, and manufacturing of surfaces of metals, alloys, ceramics, and other materials. Laser cladding technology has the advantages of high efficiency, high accuracy, and the ability to achieve multi material composites, and is widely used in automotive, aerospace, shipbuilding, medical and other fields. However, there are also some problems with laser cladding technology, such as unstable weld pool morphology, uneven weld pool depth, and thermal stress, which limit its application range and the need to improve efficiency. Therefore, how to further improve the efficiency and quality of laser cladding technology has been an important research direction for researchers. Through nine orthogonal experiments without electromagnetic field, the effects of laser processing parameters, such as laser power, spot diameter, and scanning speed, on the quality of the cladding layer were studied. For melting height, scanning speed is the most significant influencing factor; For the melt width, the spot diameter is the most significant influencing factor; For the penetration depth, the laser power is the most significant factor. Through comprehensive comparison of subsequent morphology observation and mechanical property testing, it is concluded that laser power of 1500W, spot diameter of 3mm, and scanning speed of 4mm/s are the best process parameters, providing guidance for subsequent cladding experiments.

Microstructure, mechanical property and bonding mechanism of SiC ceramic joint using a novel Y2Si2O7/Mullite glass-ceramic interlayer

Joining of SiC ceramics with a pre-oxidized or unoxidized surface and the subsequent mechanical properties have been studied using Y2O3–Al2O3–SiO2 glass bonding method, and the mechanism of interface bonding was revealed. The joining parameter of interest was temperature from 1400 °C to 1500 °C for a dwell time 10 min. The microstructure, compositions, and interfacial properties were characterized via electron microscopy and X-ray diffractometry. A multiphase glass-ceramic interlayer mainly consisting of Y2Si2O7 and mullite was formed in the joint, which possessed good thermal matching with the SiC substrate. Moreover, the softening temperature of glass-ceramic could exceed to 1200 °C. The joint obtained from the pre-oxidized SiC substrate exhibited a more reliable interface bonding than the unoxidized surface. A preferable shear strength of 48 MPa was achieved within 10 min at 1420 °C. The elemental diffusion at the interface and the chemical bonding between glass-ceramic and SiC contributed to a reliable SiC–SiC joint.

Individual effect of Y and Nd on the microstructure formation of Mg-Y-Nd alloys processed by severe plastic deformation and their effect on the subsequent mechanical and corrosion properties

This work investigated the effect of sole yttrium and neodymium alloying on the microstructure formation during severe plastic deformation by equal channel angular pressing (ECAP) and an impact on the mechanical strength and corrosion resistance of binary Mg-3Y and Mg-3Nd alloys. The results are compared with a ternary Mg-4Y-3Nd alloy, which represents a simplified version of the commercially successful WE43 alloy. The extensive study comprises a thorough microstructural analysis performed by scanning and transmission electron microscopy, including electron backscatter diffraction and texture analysis performed by X-ray diffraction. It is shown that the presence of Nd primarily caused precipitation during the processing of the Mg-3Nd alloy, while Y remained dissolved in the magnesium matrix in the Mg-3Y alloy. This difference resulted in a significantly smaller average grain size in the Mg-3Y alloy (∼0.77 nm) than in the Mg-3Nd alloy (∼1.3 μm) after the final step of the processing and formation of a slightly different texture. Consequently, the composition and the processing affected the mechanical and corrosion properties of the investigated materials, measured by compression deformation tests, microhardness measurement, and electrochemical impedance spectroscopy. This study shows that the ECAP-processed W3 sample exhibits a surprisingly good combination of ultrafine-grain structure, weak crystallographic texture, high strength, and high corrosion resistance compared with the other investigated samples. These attributes make this material very interesting for utilisation in the industry and/or medicine.

High Cycle Fatigue and Very High Cycle Fatigue of Orthorhombic (O + α<sub>2</sub>)-Type Ti–27.5Nb–13Al Alloy with and without B and Fatigue Striation Analysis in Comparison with (α + β)-Type Titanium Alloys

The lightweight and high strength Ti–27.5Al–13Nb intermetallic alloy, based on the orthorhombic Ti2AlNb phase (O phase) and the α2 phase incorporated, was previously developed by the authors. This alloy would seem to have good potential for applications where fatigue behavior is a main concern, such as automobile and aircraft engine parts. The minor addition of boron (B) is known to refine the ingot grain size and thus to improve the subsequent mechanical properties. For these reasons, the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of B-free and 0.1 pct B-modified Ti–27.5Al–13Nb alloy were examined in the present study. HCF tests were performed at room temperature (RT) in tension-tension mode at an R of 0.1 and a frequency of 10 Hz, while VHCF tests were performed using an ultrasonic resonance fatigue test machine at an R of −1 and a frequency of 20 kHz. In both fatigue tests, hourglass-shaped specimens were used. With the addition of 0.1 pct B, the prior B2 grain size of an ingot was reduced drastically, from 600∼1000 µm for the B-free alloy to 100∼250 µm. The 0.1 pct B-modified Ti–27.5Al–13Nb alloy with a duplex microstructure consisting of a globular α2 phase and a lamellar microstructure exhibited superior elongation of 6.1 pct at RT. The HCF curve for this alloy with a duplex microstructure was almost the same as that for a Ti–6Al–4V alloy with a fully lamellar microstructure. Although prolonged fatigue life was previously reported in the HCF region in the 0.1 pct B-modified Ti–6Al–4V alloy, the addition of 0.1 pct B to the Ti–27.5Al–13Nb, Ti–6Al–4V and Ti–4Al–2.5V–1.5Fe alloys had no such effect in the VHCF region. VHCF strength for a lamellar microstructure was ranked in the order of Ti–4Al–2.5V–1.5Fe, Ti–6Al–4V and Ti–27.5Al–13Nb from the highest. Well-defined striations were observed at the propagation stage area of the fatigue fracture surface of B-free Ti–27.5Al–13Nb, and the measured striation spacing kept a constant of 0.29 µm through the propagation distance of 300 µm. The calculation based on this observation showed that the fatigue life spent in the propagation stage was very short and thus almost 100 pct of HCF life was thought to be spent in the fatigue initiation stage. For the B-free Ti–6Al–4V alloy with an equiaxed microstructure, the striation spacing increased from 0.06 µm to 4 µm as the fatigue crack propagated for a distance of 1,000 µm. Calculation based on the striation spacing revealed that, similar to the case with the Ti–27.5Al–13Nb alloy, the fatigue initiation stage consumed almost 100 pct of fatigue life regardless of the B addition.

Prediction of the temperature recorded in lap joint at during the friction stir welding

The objective of the present work is the modelling of parameters influencing the temperature during friction stir lap welding. The area of physical understanding is the influence of the tool pin geometry and material on the temperature field, microstructural refinement, resulting material flow, and the influence of flow variations on the subsequent mechanical properties of FSW butt lap joints in aluminium 3003 Alloy. The results obtained allowed us to propose a mathematical model to study the interactions between different factors. Thus, it was shown that the most influential parameters are respectively the rotational speed and weld speed.

Flexural characteristics of material extrusion steel 316L: Influence of manufacturing parameters

• Material Extrusion Steel 316L specimens build with different raster angles and layer heights were tested under bending loading, under ‘on edge’ and ‘flat’ orientation; • Comparable flexural strength results were obtained for the two print orientations; • The ‘on edge’ print orientation specimens outperformed the flat orientation specimens; • The ±30° raster angled specimens outperformed all other specimens in both the print orientations, recording the highest flexural strengths; • Uniform deformation modes of the specimens were evidenced from the digital image correlation analysis. This short communication paper reports the effects of manufacturing parameters (raster angle, layer height, and print orientation) on the flexural properties of material extrusion (ME) Ultrafuse Steel 316L. Flexural specimens were produced with four raster angles: ±30°, ±45°, ±75°, and 0°/90°, with each raster angle printed at three layer heights: 0.1, 0.15, and 0.2 mm. The former combinations were of ‘flat’ print orientation, and a limited amount of ‘on-edge’ print orientation specimens were included for a general comparison. Statistical analysis was performed on the flexural strength data. Furthermore, the digital image correlation (DIC) technique was employed to study the deformation modes/mechanisms of the specimens. Comparable flexural strength results were obtained for the two print orientations. However, the ‘on edge’ print orientation specimens outperformed their counterparts. The ±30° raster angled specimens outperformed all other specimens in both the print orientations, recording the highest flexural strengths. Uniform deformation modes of the specimens were evidenced from the DIC analysis, where the effects of internal voids/porosity on subsequent mechanical properties were found to be minor. Overall, the results presented herein will increase confidence in employing the ME process for Steel 316L for applications involving bending loads.

On the short-time thermal phase-stability of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy

The present work deals with the short-time thermal phase-stability of the as-cast eutectic AlCoCrFeNi2.1 high entropy alloy. Toward this end, the effect of different temperatures (800–1000 °C) and soaking times (15–60 min) on the stability of primary dendritic regions and formation of the ordered phases was explored. Microstructural characterization was supported by thermodynamic calculations and assessment of the subsequent mechanical properties. Upon the increase in annealing temperature and soaking time, the primary FCC dendritic areas grown and destabilized owing to elemental partitioning. This was followed by dendrite fragmentation and formation of needle shape B2 ordered phases within the primary FCC regions. Despite the unstable nature of the primary constituent phases, the material hardness increased considerably to a peak point corresponding to the moderate soaking time of 45 min. The variation of the subsequent mechanical properties was discussed relying on the characteristics of the ordered and primary phases.

Effects of initial microstructure on the aging behavior and subsequent mechanical properties of Ti–Nb–O titanium alloy

Effects of initial microstructure on the aging behavior and subsequent mechanical properties of Ti–Nb–O titanium alloy

Secondary Nucleation-Triggered Physical Cross-Links and Tunable Stiffness in Seeded Supramolecular Hydrogels.

Mechanistic understanding and the control of molecular self-assembly at all hierarchical levels remain grand challenges in supramolecular chemistry. Functional realization of dynamic supramolecular materials especially requires programmed assembly at higher levels of molecular organization. Herein, we report an unprecedented molecular control on the fibrous network topology of supramolecular hydrogels and their resulting macroscopic properties by biasing assembly pathways of higher-order structures. The surface-catalyzed secondary nucleation process, a well-known mechanism in amyloid fibrilization and chiral crystallization of small molecules, is introduced as a non-covalent strategy to induce physical cross-links and bundling of supramolecular fibers, which influences the microstructure of gel networks and subsequent mechanical properties of hydrogels. In addition, seed-induced instantaneous gelation is realized in the kinetically controlled self-assembled system under this study, and more importantly, the extent of secondary nucleation events and network topology is manipulated by the concentration of seeds.

Assessing the mechanical behavior of glass and basalt reinforced vinyl ester composite under artificial seawater environment

Glass and basalt fiber reinforced vinyl ester epoxy (GFRP and BFRP) composites offer considerable potential for underwater and deep sea applications. In spite of their increasing usage in various sectors, there are still questions concerning their long term reliability in marine environment. In this article, the response of GFRP and BFRP to seawater ageing and their subsequent mechanical properties were evaluated. The composites were fabricated by vacuum assisted resin injection technique and seawater aged at 30 0C for 18, 28, 38, 258 and 305 days. By using scanning electron microscope (SEM), the failure of dry and seawater aged specimen after mechanical testing showed fiber breaking, debonding and sporadic fracturing along the laminate. This was due to higher moisture concentration in these areas during ageing. The results also revealed an overall steady decrease in tensile, flexural and impact strengths of seawater aged laminates with increasing ageing duration. Overall, the seawater ageing property of BFRP composites is almost identical to that of GFRP. The use of different nano-materials could also be explored in future works to address some drawbacks in the fiber–matrix interface durability after seawater ageing.

Mechanical performance improvement of Al–Cu–Mg using various thermomechanical treatments

A thermomechanical treatment (TMT) geared to stimulate solute atom clustering was devised to achieve a comprehensive balance of engineering properties in an Al–Cu–Mg alloy. The effect of the TMT on the microstructure and properties of an AA2524 like Al–Cu–Mg alloy were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and atom probe tomography (APT) along with tensile testing and fatigue crack growth testing. Our goal was to exceed threshold levels for fatigue crack growth (FCG) resistance, ductility and strength, using the T3 condition as a benchmark. During the TMT, dislocations and vacancies were introduced by solution treatment, quenching and pre-ageing, followed by asymmetric rolling. This enables short-circuit diffusive pathways that facilitate the formation of Mg–Cu co-clusters that effectively regulate the subsequent precipitation and influence mechanical properties. The contribution to critically resolved shear stress (CRSS) of these clusters of TMT alloys was significantly higher than the T3 state. It is proposed that Goss-grain orientations and shear textures introduced by the asymmetric rolling are also partly responsible for the enhancement of FCG resistance. The potential for solute clusters to contribute to fatigue properties is discussed in terms of the cyclic deformation shearing them, thus liberating their solute which can then bind with vacancies that would otherwise condense at the crack tip.

Effect of increased stretching deformation at cryogenic temperature on the precipitation behavior and mechanical properties of 2060 Al–Li alloy

A three-step process, which involved solution treatment, stretching deformation at cryogenic temperature, and artificial aging treatment, is a potential route to fabricate complex shaped thin-walled components of aluminum alloy. This study analyzed the influence of the cryogenic stretching deformation on subsequent aging behavior and mechanical properties of 2060 Al–Li alloy. The results showed that more dislocations accumulated in the sample with a larger deformation due to the suppressed dynamic recovery rate at low temperature, which provided more nucleation sites for the precipitation of T1 phase, thus leading to a markedly homogeneous distribution. The increased number of T1 phase consumed many copper atoms in aluminum matrix, which resulted in the decrease of the nucleation and growth rate of the θ′ phase. Optimized after-aging mechanical properties were obtained by increasing the stretching strain to 16%, with a yield strength of 538 MPa, an ultimate strength of 560 MPa, and a fracture elongation of 10.1%. The high strength resulted from the combination of precipitation strengthening and retained dislocation strengthening. The reason why the alloy still maintains a high ductility after being subjected to a larger stretching deformation was its high homogeneous deformation ability at cryogenic temperature. The further increase of the deformation resulted in the formation of defects, such as slip bands, and micro-cracks in the sample, leading to decreased after-aging ductility.