Decrease In Ultimate Tensile Strength Research Articles

The antimicrobial bio-nanocomposite containing non-hydrolyzed cellulose nanofiber (CNF) and Miswak (Salvadora persica L.) extract

Miswak (Salvadora persica L.) root extract (SPE) is known for its high antimicrobial and antioxidant activities. In this study, antimicrobial nanocomposites were prepared based on carboxymethyl cellulose (CMC), cellulose nano-fiber (CNF) and SPE. Scanning electron microscopy (SEM) was used distribution of CNF in CMC matrix and energy-dispersive X-ray (EDX) spectroscopy proved the existence of minerals and sulfur-containing compounds in SEP-activated nanocomposite. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used for CNF and SPE effects on structure of resulted nanocomposite. Incorporation of CNF increased the ultimate tensile strength (UTS) and decreased the elongation at break point (EB) while adding of 200 and 400 mg/ml caused increase of EB without decrease of UTS. Thermal gravimetric analysis (TGA) showed that SPE improved the heat stability of the nanocomposites. The pure SPE and SPE-activated nanocomposites showed good antibacterial effect against both Staphylococcus aureus (gram positive) and Escherichia coli (gram negative) bacteria.

Impact of Non-Reactive Ceria Nanoparticles on the Wettability and Reaction Kinetics Between Lead-Free Sn–58Bi and Cu Pad

Lead-free Sn–58Bi–xCeO2 (x in wt% = 0, 0.3, 0.6 and 0.9) composite solder was prepared via mechanical blending and melting route. The ceria nanoparticles (CeO2) were prepared from chemical precipitation method. Further, the variation in microstructure and phase composition, melting point, wetting and mechanical properties were studied through scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, differential scanning calorimetry, spreading ratio, contact angle and tensile testing, respectively. It was shown that Sn–58Bi–xCeO2 composite solders show 16.66 and 32.05% increase in spread ratio and wetting angle, respectively, due to the enhanced melt fluidity up to x = 0.6. The fraction of hard Bi-phase was also refined simultaneously. The tensile results showed a slight decrease in ultimate tensile strength and enhancement in ductility up to x = 0.3 and 0.6 except at x = 0.9. High temperature aging also demonstrated a reduced intermetallic compounds thickness when fraction of ceria nanoparticles in the matrix was up to x = 0.6. It is suggested that for optimum set of soldering properties, the concentration of the nanoparticles should be at 0.6 wt% in the monolithic Sn–58Bi alloy.

Electrical, mechanical and thermal properties of graphene nanoplatelets reinforced UHMWPE nanocomposites

Here, we report the electrical, mechanical and thermal properties of ultrahigh-molecular-weight polyethylene (UHMWPE) nanocomposites reinforced with 0.1 wt% to 10 wt% of graphene nanoplatelets (GNP). The electrical conductivity of GNP/UHMWPE nanocomposites shows percolation threshold at 3.0 wt% of GNP. A significant increase in electrical conductivity from 10−15 S cm−1 for neat UHMWPE to 10−5 S cm−1 at 3.0 wt% GNP loading of GNP/UHMWPE nanocomposite (i.e. 10 orders of magnitude higher) is due to the formation of an almost three-dimensional conductive network. The highest value of electrical conductivity (1.09 S cm−1) is observed at 10.0 wt% of GNP loading. The elastic modulus and yield strength increase by 30% and 21%, for the addition of 0.5 wt% and 1.0 wt% of GNP, respectively, while fracture toughness and the ultimate tensile strength decrease significantly above 0.5 wt% GNP loading. This study demonstrates the fabrication of GNP/UHMWPE bio-nanocomposites, which exhibit electrical properties useful for smart biomedical implants.

Experimental investigation and phase diagram of CoCrMnNi–Fe system bridging high-entropy alloys and high-alloyed steels

An investigation of equiatomic and non-equiatomic high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) was carried out by performing both thermodynamic calculations and experiments. The design strategy of the alloys was based on a constant valence electron concentration (VEC) of 8 while varying the content of Fe in a Fex(CoCrMnNi)100−x where x = 00, 20, 40, and 60. The X-ray diffraction results showed that the alloys have a single face-centered cubic structure at 900 °C. The tensile test results revealed that both the yield strength and ultimate tensile strength decrease as the amount of Fe is increased but the uniform elongation increases. Additionally, the strain-hardening rate is significantly enhanced at higher Fe concentrations due to the activation of deformation twinning as an additional deformation mechanism. Interestingly, the critical twinning stress is significantly reduced as the Fe content is increased from Fe00 to Fe60. As a result, the deformation twins were easily activated in a specimen deformed up to a true strain of 20% for Fe60, unlike the other alloys, which exhibited no deformation twinning at the same true strain. Furthermore, it was revealed that the frequency of deformation twinning increases proportionally with increase in the Fe content.

Characterization of Mechanical Properties of Epoxy Reinforced with Glass Fiber and Coconut Fiber

The present work deals with the characterisation polymer matrix composites combining glass fiber and fiber got from coconut. The composite was prepared using hand layup process and sufficient precaution has been taken to ensure there is homogeneity. The composite is composed of 60% epoxy resin, 10% glass fiber and 30% coconut fiber. Various mechanical tests like micro hardness test, tensile strength, impact strength test has been carried out to characterise the composite. The various mechanical properties like density, micro hardness and tensile strength are affected when the coconut fibers were added. The impact strength and flexural strength of the composite increases while ultimate tensile strength decreases. The study has come up with prospective results and further research has to be done to examine the effect of fiber content, fiber orientation, loading pattern etc. Studies on corrosive wear and other tribological properties can reveal newer things, which can enable us to use the composite that is combination of epoxy and coconut fibers in newer and newer applications.

Experimental Metabolic Syndrome Model Associated with Mechanical and Structural Degenerative Changes of the Aortic Valve

The purpose of this study was to test the hypothesis that an experimental high fat (HF) animal with metabolic syndrome results in structural degeneration of the aortic valve. Domestic pigs were divided (n = 12) and administered either a normal or HF diet. After 16-weeks, the HF diet group had increased weight (p ≤ 0.05), total cholesterol (p ≤ 0.05), and systolic and diastolic pressure (p ≤ 0.05). The aortic valve extracellular matrix showed loss of elastin fibers and increased collagen deposition in the HF diet group. Collagen was quantified with ELISA, which showed an increased concentration of collagen types 1 and 3 (p ≤ 0.05). In the HF diet group, the initial stages of microcalcification were observed. Uniaxial mechanical testing of aortic cusps revealed that the HF diet group expressed a decrease in ultimate tensile strength and elastic modulus compared to the control diet group (p ≤ 0.05). Western blot and immunohistochemistry indicated the presence of proteins: lipoprotein-associated phospholipase A2, osteopontin, and osteocalcin with an increased expression in the HF diet group. The current study demonstrates that experimental metabolic syndrome induced by a 16-week HF diet was associated with a statistically significant alteration to the physical architecture of the aortic valve.

Effect of temperature on tensile mechanical properties of GFRP bars with different diameters

Tensile mechanical properties of glass fiber reinforcement polymer (GFRP) bars under temperature effect is very important for engineering application. Based on three types of GFRP bars with different diameters under elevated and low temperature, change law of ultimate tensile strength and tensile elastic modulus in the temperature range of -20 °C to 300 °C were studied on GFRP bars. The results show that ultimate tensile strength decreases with the rise of temperature from -20 °C to 300 °C. Ultimate tensile strength and tensile elastic modulus decrease linearly below 100 °C. Above 100 °C, ultimate tensile strength decreases faster, temperature is higher. These

Study of heat treatment parameters for additively manufactured AlSi10Mg in comparison with corresponding cast alloy

A solution, quenching and ageing heat treatment is often performed on additive manufactured AlSi10Mg parts to dissolve the anisotropy due to the layer-by-layer building.This study investigates the influence of temperature and duration of solution and ageing treatment on microstructure, hardness and density of AlSi10Mg alloy produced by direct metal laser sintering.A parallel investigation is carried out on AlSi10Mg samples produced by gravity casting to analyse the different response to the same heat treatment conditions.The highest hardness, combined with an acceptable increase of porosity, is reached after selected heat treatment parameters. It was also found that, compared to the as-produced condition, this treatment leads to a decrease of ultimate tensile strength, without affecting the yield strength of additive manufactured samples, and reduces the difference in properties along the two building directions. The high properties of the as-produced samples are related to the finer microstructure and, as proved by the differential scanning calorimetric measurements, to the self-quenching phenomenon.

Dependence of mechanical properties on the microstructural parameters of TA15 titanium alloy with tri-modal microstructure

Revealing the microstructural parameters-mechanical properties relationship is very critical for the microstructure tailoring and properties optimization of titanium alloy. In this work, the dependence of mechanical properties on microstructural parameters of TA15 titanium alloy with tri-modal microstructure was investigated. The results indicate that at a certain lamellar α (αl) content (28%), both of yield strength (σ0.2) and ultimate tensile strength (σb) decrease continuously with the increase of equiaxed α (αp) content, while the decrease speed slows down at higher αp content. At a certain content of αp of 20%, σ0.2 and σb both increase first and then decrease as the content of αl increases. The above effect laws result from the competition between the softening effect caused by increasing the softer αp and αl contents and the strengthening effect relating to αl/βt interfaces and βt hardening. As for the elongation (δ) and reduction of area (Φ), they show an increase trend with αp content increasing at a certain αl content of 28%. However, they decrease first and then increase with αl content increasing at a certain αp content of 20%. The early plasticity decrease at lower αl content is due to the popular rapid void nucleation and cleavage fracture along αl/βt interfaces. When αp or αl content increases to higher level, the deformation compatibility and homogeneity improves, which suppress the rapid void nucleation and cleavage fracture along αl/βt interfaces. Meanwhile, the fracture mechanism changes from the coexistence of void coalescence and cleavage fracture to the void coalescence dominated fracture, thus the plasticity increases. Moreover, a back-propagation neural network model was developed to correlate the mechanical properties with microstructural parameters of tri-modal microstructure. The prediction results suggest that better combination of strength and plasticity can be achieved by controlling the contents of αp and αl in the range of 10–15% and 22–27%, respectively.

Effect of Si addition and applied pressure on microstructure and tensile properties of as-cast Al-5.0Cu-0.6Mn-1.2Fe alloys

Abstract The effects of Si addition and applied pressure on the microstructure and tensile properties of as-cast Al-5.0Cu-0.6Mn-1.2Fe alloys were studied. The results show that Si addition promotes the formation of Chinese script α-Fe, and suppresses the precipitation of Al3(FeMn) and Al6(FeMn). For the alloys produced without pressure, Si addition increases the volume fraction of porosity, resulting in remarkable decrease in ultimate tensile strength (UTS) and yield strength (YS). For the alloys produced with 75 MPa pressure, Si addition improves UTS and YS owing to the formation of high number density of Al2Cu (θ) phases. The tensile properties of alloys increase with increasing applied pressure at the same Si content level, which is attributed to elimination of porosity, grain refinement strengthening and solid-solution strengthening. The alloy with 1.1% Si addition and 75 MPa pressure shows the best tensile properties, where the UTS, YS and elongation are 237 MPa, 140 MPa and 9.8%, respectively.

Microstructures and mechanical properties of Cu-Sn alloy subjected to elevated-temperature heat deformation

Cu-Sn alloy was subjected to elevated-temperature isothermal compression with 0.01 s−1 strain rate and 500 ∼ 700 °C temperature range. The thermal compression curve reflected a competing process of work hardening versus dynamic recovery (DRV) and recrystallization, which exhibited an obvious softening trend. Meanwhile, high-temperature deformation and microstructural features in different regions of the alloy was analyzed through EBSD. The results show that grains grow as the temperature rises, competition among recrystallization, substructural, and deformation regions tends to increase with the increase of temperature, and distribution frequency of recrystallization regions gradually increases and then drops suddenly at 650 °C. At 500 ∼ 550 °C, preferentially oriented texturing phenomenon occurs, low angle boundaries(LABs) are gradually transformed into high angle boundaries (HABs) and the Σ (CSL) boundaries turn gradually into Σ3 boundaries. In tensile test of tin bronze, elongation at break increases slowly, whereas yield strength (YS) and ultimate tensile strength (TS) decrease gradually.

Influence of Yttria on Oxide Dispersion Strengthened (ODS) Ferritic Steel

Oxide dispersion strengthened (ODS) ferritic steels are the most promising candidate materials for advanced fast breeder reactors of future. They exhibit excellent swelling, corrosion resistance and superior high temperature strength. Fe-18Cr-2W-0.2Ti-(0.3-0.5)Y2O3 (all in wt.%) alloys were prepared by mechanical alloying of elemental powders in Zoz Simoloyer attritor. The mechanical alloyed powders were heated in hydrogen atmosphere at 1423K in a steel can. The can was hot forged in a 100ton friction screw forging press. Increase in yttria content from 0.3 to 0.5wt.% causes a decrease in ultimate tensile strength and ductility. Reasons for this are discussed. Observed properties are related with the microstructure.

Effects of strain rate on mechanical properties and deformation behavior of an austenitic Fe-25Mn-3Al-3Si TWIP-TRIP steel

The effects of quasi-static and low-dynamic strain rate (ε̇ = 10−4 /s to ε̇ = 102 /s) on tensile properties and deformation mechanisms were studied in a Fe-25Mn-3Al-3Si (wt%) twinning and transformation-induced plasticity [TWIP-TRIP] steel. The fully austenitic microstructure deforms primarily by dislocation glide but due to the room temperature stacking fault energy [SFE] of 21 ± 3mJ/m2 for this alloy, secondary deformation mechanisms such as mechanical twinning (TWIP) and epsilon martensite formation (TRIP) also play an important role in the deformation behavior. The mechanical twins and epsilon-martensite platelets act as planar obstacles to subsequent dislocation motion on non-coplanar glide planes and reduce the dislocation mean free path. A high-speed thermal camera was used to measure the increase in specimen temperature as a function of strain, which enabled the use of a thermodynamic model to predict the increase in SFE. The influence of strain rate and strain on microstructural parameters such as the thickness and spacing of mechanical twins and epsilon-martensite laths was quantified using dark field transmission electron microscopy, electron channeling contrast imaging, and electron backscattered diffraction. The effect of sheet thickness on mechanical properties was also investigated. Increasing the tensile specimen thickness increased the product of ultimate tensile strength and total elongation, but had no significant effect on uniform elongation or yield strength. The yield strength exhibited a significant increase with increasing strain rate, indicating that dislocation glide becomes more difficult with increasing strain rate due to thermally-activated short-range barriers. A modest increase in ultimate tensile strength and minimal decrease in uniform elongation were noted at higher strain rates, suggesting adiabatic heating, slight changes in strain-hardening rate and observed strain localizations as root causes, rather than a significant change in the underlying TWIP-TRIP mechanisms at low values of strain.

High strength SiCp/AZ91 composite assisted by dynamic precipitated Mg17Al12 phase

The 5μm10 vol % SiCp/AZ91 composite was extruded successfully at 250 °C by the slow speed extrusion (0.01, 0.1 and 1 mm/s). Results indicated that the composite with the yield strength of ∼371.5 MPa and ultimate tensile strength of ∼443.9 MPa exhibited much higher tensile strength than present particle reinforced magnesium matrix composites (PMMCs). Such high tensile strength in present work might be attributed to ultra-fine grains and submicron sized Mg17Al12 phases precipitated during extrusion. As the extrusion speed increased from 0.01 to 1 mm/s, both the average size of grains and Mg17Al12 phase increased, while volume fraction of Mg17Al12 phase decreased. All these led to the decrease of yield strength and ultimate tensile strength, however, accompanied by the increase of elongation.

Effect of paint baking treatment on the properties of press hardened boron steels

This study comprehends the effect of a typical paint baking process on the properties of press hardened boron steels. Bake hardening response of four 22MnB5 steels with different production histories and two other boron steels of 30MnB5 and 34MnB5 type were analyzed. In particular, the effect of steel carbon content and prior austenite grain size on the strength of the bake hardening treated steels was investigated. Press hardened steels showed a relatively strong bake hardening effect, 80–160MPa, in terms of yield strength. In addition, a clear decrease in ultimate tensile strength, 30–150MPa, was observed due to baking. The changes in tensile strength showed a dependency on the carbon content of the steel: higher carbon content led to a larger decrease in tensile strength in general. Smaller prior austenite grain size resulted in a higher increase in yield strength despite the micro-alloyed 34MnB5. Transmission electron microscopy analysis carried out for the 34MnB5 revealed niobium rich mixture carbides of (Nb, Ti)C, which have most likely influenced the different bake hardening response. The present results indicate that the bake hardening response of press hardened steels depends on both prior austenite grain size and carbon content, but is also affected by other alloying elements. The observed correlation between prior austenite grain size and bake hardening response can be used to optimize the production of the standard grades of 22MnB5 and 30MnB5. In addition, our study suggests that baking process improves the post-uniform elongation and ductile fracture behavior of 34MnB5, but do not significantly influence the ductile fracture mechanisms of 22MnB5 and 30MnB5 representing lower strength levels.

Effect of Coiling Temperature on Microstructure, Properties and Resistance to Fish-Scaling of Hot Rolled Enamel Steel.

The microstructure, mechanical properties, and hydrogen permeation behavior of hot rolled enamel steel were investigated. Three coiling temperatures were adopted to gain different sizes of ferrite grain and TiC precipitates. The results show that a large number of interphase precipitates of nano-sized TiC can be obtained at coiling temperatures of 650 and 700 °C, while a few precipitates are found in experimental steel when coiling temperature is 600 °C. The yield strength and ultimate tensile strength decrease with increasing coiling temperature, while elongation increases. The experimental steel has the best resistance to fish-scaling at coiling temperature of 700 °C, due to the large quantities of nano-sized interphase precipitates of TiC.

Microstructural evolution and mechanical characterization for the A508–3 steel before and after phase transition

Nuclear power, as a reliable clean and economical energy source, has gained great attention from all over the world. The A508–3 steel will be introduced as the structural materials for Chinese nuclear reactor pressure vessels (RPVs). This work investigated the temperature–dependence microstructural evolution during high–temperature heat treatments, and built the relationship between the microstructure and mechanical properties for the steel before and after phase transition. The results show that the original steel consists of the bainite, allotriomorphic ferrite, retained austenite and few Mo–rich M2C carbides. The phase–transition temperature of the steel is determined to be 750 °C. The tensile tests performed at 20–1000 °C indicate that both of the yield strength and ultimate tensile strength decrease monotonously with increasing the temperature. Before phase transition, precipitation of cementite from the retained austenite and coarsening of cementite at the austenite–ferrite interphases should be responsible for their sharp decrease. After phase transition, the growth of austenite grain reduces the strength moderately. As for the elongation, however, it increases dramatically when the testing temperature is over 750 °C, due to the dissolution of cementite and formation of austenite. The obtained results will provide some fundamental data to understand and implement the In–Vessel Retention strategy.

Crystal growth and morphology evolution of D88 (Mn, Fe)5Si3 phase and its influence on the mechanical and wear properties of brasses

The crystal growth and morphology evolution of D88 transition metal silicide and its influence on the mechanical properties of alloys have yet to be determined. In this paper, the effect of in situ-formed D88 (Mn, Fe)5Si3 phase on the mechanical and wear performances of brasses is presented. By means of deep etching and phase extraction technologies, the morphology of (Mn, Fe)5Si3 phase is found to exhibit long hexagonal prism, due to the higher growth velocity in the <0001> direction than that of <11 2̅ 0> according to the Mn–Si bond chain arrangement. Two kinds of hollows, i.e. internal hollow and prism facet hollow, are formed on the coarse primary (Mn, Fe)5Si3 prisms, which can be ascribed to the restrained solute diffusion within the prism and attachment limited kinetics on the prism facet, respectively. With increasing the (Mn, Fe)5Si3 content, the hardness and yield strength increase effectively, which mainly results from the load transferring effect and grain refinement, supported by the good agreement between calculated and experimental results. The fracture mode transforms from ductile failure to quasi-cleavage and cleavage failure. Severe cracking tendency of high aspect ratio primary (Mn, Fe)5Si3 particles containing large-sized hollows leads to slight increment in ultimate tensile strength and great ductility decrease at high (Mn, Fe)5Si3 content. In addition, the fine eutectic (Mn, Fe)5Si3 particles are beneficial to improve the ductility by acting as effective barriers to crack cleavage and void growth. The proper combination of thinner primary and eutectic (Mn, Fe)5Si3 particles is found to efficiently restrain the crack creation and result in a good wear resistance. This study may be helpful to design high performance alloys reinforced with transition metal silicides by tailoring their morphology.

Effect of trace HA on microstructure, mechanical properties and corrosion behavior of Mg-2Zn-0.5Sr alloy

Effect of the addition of trace HA particles into Mg-2Zn-0.5Sr on microstructure, mechanical properties, and bio-corrosion behavior was investigated in comparison with pure Mg. Microstructures of the Mg-2Zn-0.5Sr-xHA composites (x=0, 0.1 and 0.3wt%) were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Results of tensile tests at room temperature show that yield strength (YS) of Mg-2Zn-0.5Sr/HA composites increases significantly, but the ultimate tensile strength (UTS) and elongation decrease with the addition of HA particles from 0 up to 0.3wt%. Bio-corrosion behavior was investigated by immersion tests and electrochemical tests. Electrochemical tests show that corrosion potential (Ecorr) of Mg-2Zn-0.5Sr/HA composites significantly shifts toward nobler direction from −1724 to −1660mVSCE and the corrosion current density decreases from 479.8 to 280.8μAcm−2 with the addition of HA particles. Immersion tests show that average corrosion rate of Mg-2Zn-0.5Sr/HA composites decreases from 11.7 to 9.1mm/year with the addition of HA particles from 0wt% up to 0.3wt%. Both microstructure and mechanical properties can be attributed to grain refinement and mechanical bonding of HA particles with second phases and α-Mg matrix. Bio-corrosion behavior can be attributed to grain refinement and the formation of a stable and dense CaHPO4 protective film due to the adsorption of Ca2+ on HA particles. Our analysis shows that the Mg-2Zn-0.5Sr/0.3HA with good strength and corrosion resistance can be a good material candidate for biomedical applications.

Effect of Nickel Contents on the Microstructure and Mechanical Properties for Low-Carbon Bainitic Weld Metals

Multi-pass weld metals were deposited on Q345 base steel using metal powder-flux-cored wire with various Ni contents to investigate the effects of the Ni content on the weld microstructure and property. The types of the microstructures were identified by optical microscope, scanning electron microscope, transmission electron microscope, and micro-hardness tests. As a focusing point, the lath bainite and lath martensite were distinguished by their compositions, morphologies, and hardness. In particular, a number of black plane facets appearing between lath bainite or lath martensite packets were characterized by laser scanning confocal microscope. The results indicated that with the increase in Ni contents in the range of 0, 2, 4, and 6%, the microstructures in the weld-deposited metal were changed from the domination of the granular bainite to the majority of the lath bainite and/or the lath martensite and the micro-hardness of the weld-deposited metal increased. Meanwhile, the average width of columnar grain displays a decreasing trend and prior austenite grain size decreases while increases with higher Ni content above 4%. Yield strength and ultimate tensile strength decrease, while the reduction in fracture area increases with the decreasing Ni mass fraction and the increasing test temperature, respectively. And poor yield strength in Ni6 specimen can be attributed to elements segregation caused by weld defect. Finally, micro-hardness distribution in correspondence with specimens presents as a style of cloud-map.