Effect Of Second Phase Research Articles

Oxytocin is a principal hormone that exerts part of its effects by active fragments

Oxytocin is a nonapeptide consisting of a cyclic six amino-acid structure and a tail of three amino acids. It was originally known for its ability to induce milk ejection and to stimulate uterine contractions. More recently, oxytocin has been shown to stimulate social behaviors, and exert pain-relieving, anti-stress/anti-inflammatory and restorative effects.We hypothesize that oxytocin is a principal hormone that, in part, exerts its effects after degradation to active fragments with more specific effect profiles.Experimental findings on rats show that administered oxytocin exerts biphasic effects. For example, after an initial increase in pain threshold, a second more long-lasting increase follows. Blood pressure and cortisol levels initially increase and then reverse into a long-lasting decrease in blood pressure and cortisol. Whereas the initial effects are, the second-phase effects are not blocked by an oxytocin antagonist, but by an opioid mu-antagonist and by an alpha 2-adrenoreceptor antagonist, respectively, suggesting that other receptors are involved. Repeated administration of oxytocin induces multiple anti-stress effects, which are mediated by alpha 2-adrenoreceptors. Repeated administration of linear oxytocin and linear oxytocin fragments with a retained C-terminal reduce spontaneous motor activity, a sedative or anti-stress effect, suggesting that alpha 2-adrenoreceptors have been activated. In contrast, linear mid-fragments stimulate motor activity.Low-intensity stimulation of cutaneous nerves in rats, as well as breastfeeding and skin-to-skin contact between mothers and babies, trigger immediate anti-stress effects. Some of these effects are likely caused by open ring/linear C-terminal fragments activating alpha 2-adrenoreceptors.Oxytocin fragments may be pre-formed and released in the brain or created by metabolic conversion of the principal hormone oxytocin in the central nervous system. Oxytocin and its fragments may also be released from peripheral sites, such as peripheral nerves, the gastrointestinal tract, and blood vessels in response to decreased sympathetic or increased parasympathetic nervous tone. Smaller fragments of oxytocin produced in the periphery may easily pass the blood-brain barrier to induce effects in the brain.In conclusion, oxytocin is linked to many different, sometimes opposite effects. The intact cyclic molecule may act to initiate social interaction and associated psychophysiological effects, whereas linear oxytocin and C-terminal fragments may induce relaxation and anti-stress effects following social interaction. In this way, the principal hormone oxytocin and its fragments may take part in a behavioral sequence, ranging from approach and interaction to calm and relaxation. Linear fragments, with an exposed cysteine-residue, may exert anti-inflammatory and antioxidant effects and thereby contribute to the health-promoting effects of oxytocin.

Investigation of the effect of second phase precipitates on the corrosion and electrical conductivity of 7075 aluminum alloys

PurposeThis paper aims to investigate the effects of second phase precipitate size on microstructure, hardness, density, corrosion and electrical conductivity of 7075 aluminum alloy fabricated by the powder metallurgy method and aged at 120°C for various aging periods.Design/methodology/approachFor the aging process (T6), these alloys were solution-treated at 485°C for 2 h, quenched, aged at 120°C for four various periods and finally air cooled. After the aging process, these alloys were examined with scanning electron microscope, X-ray diffraction, density and hardness measurements. The corrosion tests were carried out using the potentiodynamic polarization technique; electrical conductivity values were measured as IACS%.FindingsResults showed that the precipitate size increased with increasing aging period and the maximum precipitate size was achieved for the sample aged for 28 h. The maximum hardness was attained for the sample aged for 24 h, while the same specimen obtained the lowest electrical conductivity and corrosion resistance.Originality/valueIn this research, second phase precipitates of heat treatment processing affected the electrical conductivity and corrosion behavior of the 7075 aluminum alloy. Also it is understood that the heat treatment period is an effective parameter on these properties.

Effects of Second Phases on Microstructure, Microhardness, and Corrosion Behavior of Mg-3Sn-(1Ca) Alloys.

The effects of second phases on microstructure, microhardness, and corrosion behavior of aged Mg-3Sn (T3) and Mg-3Sn-1Ca (TX31) alloys are investigated systematically. The thermal stability of the CaMgSn phase is higher than that of the Mg2Sn phase, and the microstructure remains essentially unchanged in the TX31 alloy after solution treatment for 28 h at 733 K. The T3 alloy exhibits double age-hardening peaks; one is 54.9 ± 2.1 HV for 7 h, and the other is 57.4 ± 2.8 HV for 15 h. However, the microhardness quickly reaches a stable value with increasing aging times in the TX31 alloy due to the no change in CaMgSn phases. It was also found by electrochemical impedance spectra that the corrosion resistance of aged T3 alloy is superior to that of aged TX31 alloy, especially T3 alloy aged for 7 h. The corrosion film of aged T3 alloy is denser, which attributes to most of dissolved Sn in the α-Mg matrix and the formation of a small quantity of tiny Mg2Sn particles, and effectively prevents the occurrence of further corrosion of the Mg matrix. However, galvanic cells formed between α-Mg and CaMgSn phases accelerate the corrosion of aged TX31 alloy.

Effect of pearlite morphology on recrystallization behaviour in cold rolled high strength automotive steel sheets

The present study is mainly focused on recrystallization behaviour and associated microstructure and texture evolution with the effect of second phase as pearlite. Two cold rolled sheets with 80% cold reduction consisted of coarse and fine pearlite bands along with ferrite. Cold rolling was followed by interrupted annealing at different soaking time to study the kinetics and recrystallization texture evolution. Results are analysed with the help of micro-Vickers hardness, microstructure and texture analysis through SEM and Electron Backscattered Diffraction (EBSD). Results clearly show the effect of pearlite band size on recrystallization kinetics and texture evolution. Faster recrystallization is observed for fine pearlite band compared to coarse band. Heterogeneous nucleation of grains took place at ferrite pearlite interface, grain boundaries of RD-ND orientations and within the deformed ferrite. Fragmentation and spherodization of pearlite lamellae takes place inside the colony of pearlite with increase in soaking time.

Effects of second phases in anode materials on discharge performance of Mg-air batteries

As-cast Mg-6Al and as-cast and hot-rolled Mg-6Al-1Ce alloys were used as anode materials in Mg-air batteries. Effects of second phases of anode materials on electrochemical properties and discharge behavior were investigated by backscattered electron (BSE), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and electrochemical test. Many β-(Mg17Al12) particles were found in as-cast Mg-6Al alloy. Deep corrosion pits were formed near these particles, which is not beneficial to improve discharge performance. The as-cast Mg-6Al-1Ce alloy forms larger γ-(Al4Ce) grains, which retard the shedding of corrosion products. The contact between electrolyte and metal anode is hindered, and corrosion product accumulation leads to a slowly decreasing voltage. With hot rolling, the γ phase breaks up into many fine and evenly distributed particles. In this way, corrosion products can easily peel off from the anode surface, leading to an improvement of anode discharge activity.

Effect of secondary phases' structure on the dielectric properties of β-SiAlON

This study investigates the effect of secondary phases microstructure on mechanical and dielectric properties in beta silicon aluminum oxy-nitride (β-SiAlON) produced by pressureless sintering at temperatures of 1650 °C–1750 °C from a mixture of silicon nitride (Si3N4), alumina (Al2O3), aluminum nitride (AlN) and yttrium oxide (Y2O3). β-SiAlON obtained at and above 1700 °C sintering temperature, which showed a fully dense structure with a good combination of hardness and strength of 21–23 GPa and 870–890 MPa, respectively. Surprisingly, the dielectric constant of β-SiAlON was found to increase significantly from 6.4 to 8.2 with an increase in the sintering temperature from 1700 to 1750 °C. Transmission electron microscopy revealed the presence of secondary crystalline phase yttrium rich silicon aluminum oxynitride in the specimen sintered at 1750 °C , whereas yttrium rich amorphous interface structure was found in the specimen sintered at 1700 °C, suggesting the importance of controlling grain boundary structures in β-SiAlON.

The Role of Second Phases on the Creep Behavior of As-Cast and Hot-Extruded Mg-Ca-Zr Alloys

The effect of second phases on the creep behavior of Mg-Ca-Zr alloys was investigated. Casting and hot-extrusion processes were performed to prepare Mg-xCa-0.5Zr (x = 0 wt.%, 0.3 wt.% and 0.6 wt.%) alloys with different morphologies and distributions of second phases. The as-cast microstructures of Mg-Ca-Zr alloys consisted of an Mg matrix and coarse Mg2Ca intermetallic compounds distributed at the grain boundaries. The hot-extruded microstructures exhibited finer Mg2Ca spherical particles and precipitates distributed homogeneously inside the matrix and along the grain boundaries. The results of creep tests suggested that the viscous glide of dislocation and dislocation climb were the dominant creep mechanisms of Mg-Ca-Zr alloys crept at 200°C. The creep property was strongly related to the morphology and distribution of the Mg2Ca phases. The finer and more homogeneously distributed particles showed a better strengthening effect than the coarser intermetallic compounds distributed along the grain boundaries.

Microstructure-based model of nonlinear ultrasonic response in materials with distributed defects

Nonlinear ultrasonic technique is one of several promising nondestructive evaluation methods for monitoring the evolution of nanosized defects such as radiation-induced defects in nuclear materials. In this work, a microstructure-based phase-field model of dynamic deformation in elastically nonlinear materials has been developed for investigating the dynamic interaction between distributed defects and a propagating longitudinal sound wave. With the model, the effect of second phase precipitates’ size and properties on the nonlinearity parameter β that describes the magnitude of the 2nd harmonic wave was simulated. The results showed that (1) the nonlinearity parameter β increases as the elastic inhomogeneity increases regardless of whether the precipitates are softer or harder than the matrix; (2) β linearly increases with the increase of lattice mismatch strain; and (3) for a given volume fraction of second phase precipitates, β strongly depends on the precipitate size. The predicted precipitate size dependence of β agrees with the experimental data. These results demonstrate that the developed model enables one to predict the contributions of different nonlinear sources to β, to explain the signal physics behind the measured nonlinear ultrasonic response, and to guide the development of nonlinear ultrasound nondestructive detection of material defects in nuclear reactor materials.

Effect of I(Mg3YZn6)-, W(Mg3Y2Zn3)- and LPSO(Mg12ZnY)-phases on tensile work-hardening and fracture behaviors of rolled Mg–Y–Zn alloys

The effects of secondary phases (W, Mg3Y2Zn3), long-period stacking-ordered (LPSO, Mg12ZnY) and icosahedral (I, Mg3YZn6) phases on the tensile properties and work-hardening behavior of Mg–Y–Zn alloys (Mg–1.32Zn–1.79Y, ZW12; Mg–4.4Zn–2.2Y, ZW42; and Mg–5.2Zn–1.1Y, ZW51) prepared after application of differential speed rolling on their cast microstructures were studied at room temperature. The volume fractions of LPSO, W and I-phase in ZW12, ZW42 and ZW51 were 4.7, 6.3 and 4.8%, respectively. The rolled alloys exhibited a similar level of yield strength but different work hardening characteristics and tensile fracture behavior. The rolled ZW51 with I-phase particles exhibited the highest work-hardening rate and the largest tensile elongation (with ductile fracture). The ZW42 with W-phase particles exhibited a work-hardening rate slightly lower than that of the rolled ZW51, despite having the larger amount of secondary phase, and premature fracture occurred far before neck formation in ZW42, while fracture occured after neck formation in ZW51. The fractured surface showed that the coherent interface between the I-phase and Mg matrix phase is significantly more resistant to cracking than is the incoherent interface between the W-phase and Mg matrix phase. The rolled ZW12 with LPSO-phase, forming a coherent interface with the Mg matrix phase, exhibited a considerably lower work-hardening rate than the rolled ZW51, though they had the similar amounts of secondary phase. Thus, the uniform strain of the rolled ZW12 was quite small compared with that of the rolled ZW51, though fracture occurred after necking in both alloys. The same work-hardening and tensile elongation behaviors were retained after annealing treatment on the rolled alloys.

Effect of secondary phases on the thermoelectric properties of Zn2GeO4 nano-crystals grown by thermal evaporation on Au coated Si substrate

This study reported the growth of Zn2GeO4 nano-crystals on Au coated Si substrate by thermal evaporation technique using vacuum tube furnace for thermoelectric power generation applications. The thermoelectric properties of nano-crystals were improved by generating the secondary phases in the grown samples using the post-growth annealing at various temperatures (600–900 °C). The low energy carriers filtered out at the interface of secondary phases and caused an enhancement in Seebeck coefficient and power factor. The emergence of secondary phases with annealing temperature was confirmed by various characterization techniques. XRD data suggested that samples annealed at 800 and 900 °C consisted of three extra secondary phases along with the phases related to Zn2GeO4, ZnO, Si and Au. Raman spectroscopy data demonstrated the presence of strong peak due to Si substrate for all samples but two weak peaks appeared at 375 and 800 cm−1 for samples annealed at 800 and 900 °C. The SEM images shows the presence of randomly oriented nano structures as annealing temperature increase up to 900 °C. The Hall measurements were also performed to strengthened our argument.

Deformation mechanism and dynamic precipitation in a Mg-7Al-2Sn alloy processed by surface mechanical attrition treatment

The effect of second phases on the deformation mechanism of as-cast, solution-treated and aged Mg-7Al-2Sn (AT72) alloys during surface mechanical attrition treatment (SMAT) was investigated. Twinning was suppressed in the alloys containing second phases, which can provide nonuniform microstructures and phase boundaries as dislocation sources. Dynamic precipitation in AT72 alloys was studied during SMAT deformation as well. Mg2Sn particles can dynamically precipitate on the surface of all AT72 alloys during SMAT process. The quantity of Mg2Sn particles in the as-cast alloy, which is determined by the initial quantity of second phases, is larger than that of T4 and T6 alloys after the SMAT process.

Effect of Ta particles on the fracture behavior of notched bulk metallic glass composites

The existence of second phase usually promotes the formation of multiple shear bands under uniaxial loading, leading to the apparent strain hardening and enhanced plasticity in bulk metallic glasses (BMGs). However, the effect of second phase on the fracture behavior of BMGs has been rarely investigated when shear banding is suppressed. In this work, the effect of Ta particles on the fracture behavior of notched bulk metallic glass composites (BMGCs) was investigated, where shear banding is suppressed due to the introduction of high triaxial stress state. With an increase in the volume fraction of Ta particles from 0 to 3.3%, the fracture strength significantly decreases from 2.70 to 1.20 GPa. Different from the vein-like patterns caused by shear banding, the fracture surface of notched BMGCs displays numerous equiaxed dimples and micro-cracks, indicating that voids nucleation and coalescence govern the fracture process. Due to the relatively weak bonding of the interface and the mechanical incompatibility between Ta particles and amorphous matrix, voids tend to nucleate at the interface during tensile deformation, giving rise to a reduction in the fracture strength of BMGCs.

Precipitation condition and effect of volume fraction on corrosion properties of secondary phase on casted super-duplex stainless steel UNS S32750

PurposeThe secondary phase decreased the corrosion resistance because of the segregation of Cr and Mo. Therefore, this paper aims to study the precipitation condition and the effect of secondary phase with volume fraction on corrosion behavior.Design/methodology/approachSecondary phase precipitated approximately from 375°C to 975°C because of saturated Cr and Mo at grain boundary by growth of austenite. Therefore, heat treatment from 800°C to 1,300°C was applied to start the precipitation of the secondary phase.FindingsThe secondary phase is precipitated at 1,020°C because of segregation by heterogeneous austenite. The growth of austenite at 1,000°C needs the time to saturate the Cr and Mo at grain boundary. When the volume fraction of austenite is 56 per cent (14 min at 1,000°C), the secondary phase is precipitated with grain boundary of austenite. The secondary phase increased the current density (corrosion rate) and decreased the passivation. That is checked to the critical pitting temperature (CPT) curves. The 1 per cent volume fraction of secondary phase decreased CPT to 60°C from 71°C.Research limitations/implicationsThe precipitation of secondary phase not wants anyone. Casted super-duplex stainless steel (SDSS) of big size precipitates the secondary phase. This study worked the precipitation condition and the suppression conditions of secondary phase.Social implicationsManufacturers need precipitation condition to make high-performance SDSS.Originality/valueThe corrosion resistance of SDSS is hard the optimization because SDSS is dual-phase stainless steel. The precipitation of the secondary phase must be controlled to optimize of the corrosion resistance of SDSS. Anyone not studied the precipitation condition of secondary phase and the effect of secondary phase with volume fraction on corrosion behavior of SDSS.

Effects of second phases on the formation mechanism and corrosion resistance of phosphate conversion film on AZ80 Mg alloy

PurposeThe formation and corrosion processes of a conversion film on the AZ80 Mg alloy with different second phases were compared to clarify the effect of microstructure on the quality of protective coatings.Design/methodology/approachThe size and distribution of second phases in the edge and central regions of the AZ80 cast ingot exhibit a great difference. The film growth processes and their corrosion resistance on the edge and central regions of the AZ80 cast ingot were investigated by scanning electron microscope observations, immersion tests and electrochemical measurements.FindingsThe results indicate that second phases act as micro-cathodes and hydrogen evolution reaction occurs on their surface, which is not beneficial for the deposition of the conversion film.Originality/valueThe conversion film formed on the central regions of AZ80 cast ingot with a low volume fraction of second phases exhibits a more uniform surface and higher corrosion resistance than that formed on the edge regions of the sample with a higher volume fraction of second phases.

Formation of Secondary Phases and Their Effect on the Mechanical Properties of Joints Formed by TLP Bonding Using Fe–B–Si Insert Metal in Duplex Stainless Steel

We studied the effects of secondary phases on the mechanical properties of joints formed by transient liquid-phase bonding in nitrogen-containing duplex stainless steel UNS S32750. Transient liquid-phase bonding was carried out using Fe–B–Si amorphous insert metal over the temperature range of 1423–1473 K for 0–1000 s under a vacuum of 5 × 10−5 Torr. Area fraction of austenite (γ) in the joint region decreased with increasing bonding temperature and holding time. In particular, when the holding time was sufficiently prolonged, γ phase-depleted region were observed in the base metal adjacent to the joint. Secondary phases formed at the joint after short holding times were predominantly chromium borides. For specimens bonded with longer holding times (up to 1000 s), boron nitrides were formed at the interface with the joint. Formation of secondary phases in a joint area during the bonding process was expressed by diffusion equation. Tensile strength was improved in accordance with increase of bonding temperature and holding time. Especially, the bonding efficiency was over 98% for the specimen held for 1000 s at 1473 K. Tensile strength of the joint after short holding times was affected by brittle residual eutectic constituents and borides, whereas tensile strength after longer holding time was influenced by boron nitride formed at the joint interface. The results showed that the mechanical properties were strongly related to the secondary phases (CrB, BN) formed during the bonding process.

Tomographic investigation of the effects of second phases on the biodegradation and nano-mechanical performance of a Mg–Zn–Ca alloy

A combination of 3D tomography techniques provides direct evidence that links the phase assemblage to the bio-corrosion behaviour of a magnesium–zinc–calcium (Mg–Zn–Ca) alloy. The true shape, connectivity and volume fraction of the components have been determined using focused ion beam (FIB) tomography. The mechanism of the effect of the components with different morphologies on biodegradation was studied with the help of FIB. Micro X-ray CT (MicroCT) was used to investigate the degradation of the magnesium (Mg) alloys after 10 days’ immersion in simulated body fluid (SBF). Furthermore, the second phases affect the mechanical performance of the alloys. Nanoindentation was used to evaluate the nanohardness and elastic modulus of the (α-Mg + Ca2Mg6Zn3) eutectic products. The amount of second phase, however, is the key controlling factor in the bio-corrosion behaviour: any effect of configuration is undetectable.

Effect of cooling rate after heat treatment on pitting corrosion of super duplex stainless steel UNS S 32750

PurposeIn this study, super duplex stainless steel (SDSS) was heat-treated. The purpose of this study is to assess the effect of the cooling rate after heat treatment on the pitting corrosion of SDSS.Design/methodology/approachThe heat treatment from 1,000°C to 1,300°C was applied to SDSS to check the effect of the cooling rate.FindingsThe heat treatment temperature produced a different SDSS microstructure, and the cooling rate led to the growth of austenite. The casted SDSS indicated the presence of heterogeneous austenite, and the precipitation secondary phase under 1.6 per cent precipitated to bare metal. By applying heat treatment and cooling SDSS, its corrosion resistance changes because of the change in the chemical composition. The cooling rate at 5,600 J/s has the highest critical pitting temperature (CPT) at 1,100°C, and the cooling rate at 1.6 J/s has the highest CPT at 1,200°C. Low cooling rate (0.4 J/s) made the secondary phase at all temperature range.Research limitations/implicationsThe effect of secondary phase not consider because that is well known to decreasing corrosion resistance.Practical implicationsSolution annealing is taken into account to optimize the corrosion resistance. But that is not consider the cooling rate at each temperature. This study assessed the effect of the cooling rate at each temperature point.Social implicationsManufacturers need to know the effect of the cooling rate to optimize the corrosion resistance, and this study can be applied in the industrial scene.Originality/valueSDSS is hard the optimization because SDSS is a dual-phase stainless steel. Corrosion resistance can be optimized by controlling heat treatment temperature and the cooling rate. Anyone not studied the effect of the cooling rate at each temperature. The effect of the cooling rate should be considered to optimize the corrosion resistance.

Effects of second phases on deformation behavior and dynamic recrystallization of as-cast Mg-4.3Li-4.1Zn-1.4Y alloy during hot compression

Hot compression and dynamic recrystallization (DRX) behavior corresponding to the second phases of as-cast Mg-4.3Li-4.1Zn-1.4Y (wt.%) alloy was investigated in the range of 250–450 °C and 0.001–10 s−1. True strain-true stress curves showed typical characteristics DRX process. Constitutive relationship yielded an average activation energy (Q) and stress exponent (n) of 147.183 kJ/mol and 5.49, respectively. The hot deformation was mainly controlled by climb of edge dislocations, which turned into cross-slip of screw dislocations at ≥400 °C. The volume fraction of second phases changed the dislocation movement and resulted in the variation of the rate-controlling mechanism. The peak power dissipation efficiency (η) was observed at 450 °C/0.1 s−1 (32%), and the corresponding uniform and fine microstructure was attributed to the dynamic precipitation and complete DRX from uniformly distributed second phase particles. A wide flow instability region was observed at all temperatures and relatively high strain rates, corresponding to the non-uniform microstructure of the incomplete DRX and deformation band composed of ultrafine DRXed grains, which resulted from local distributed second phase particles. DRX process was attributed to the nucleation at second phase particles by the mechanism of particle stimulated nucleation (PSN), and the incomplete DRX process was accompanied by the dynamic recovery (DRV) process.

Influence of Cr on microstructure and elastocaloric effect in Ni–Mn–In–Co–Cr polycrystalline alloys

Ni–Mn-based metamagnetic shape memory alloys have been proposed as potential elastocaloric refrigerants. The intrinsic brittleness of the alloys has limited their cooling application. Introducing a soft second phase is an effective way to reduce the brittleness. From the viewpoint of application, the effect of second phase on elastocaloric effect should be illustrated. In this paper, we have investigated the microstructure, martensitic transformation and elastocaloric effect of Ni45Mn37-xIn13Co5Crx (x=0,1 and 2) polycrystalline alloys. Single-phase and precipitates-containing microstructures are obtained for the undoped and doped alloys, respectively. The precipitates in Cr-doped alloys enhances the fracture strength but significantly hinders the martensitic transformation. Balancing the fracture strength and martensitic transformation, the Ni45Mn36In13Co5Cr alloy with small amount of precipitates along grain boundaries exhibits large cooling effects of 4–6 K in the temperature range of 317–353 K.

Effects of secondary phases on texture and mechanical properties of as-extruded Mg–Zn–Er alloys

Abstract The effects of kinds of secondary phases on texture and mechanical properties of Mg–Zn–Er alloys were investigated. The results suggest that the I-phase has a great effect on modification of the texture via the discontinuous dynamic recrystallization mechanism (DDRX), which tends to form well-developed equiaxed recrystallized grains. Meanwhile, the W-phase plays an important role in refining the grain size via continuous dynamic recrystallization (CDRX), companied with a higher maximum texture intensity. Thus, the Mg–6Zn–1Er alloy containing I-phase shows a performance of higher elongation of 20.4%. The Mg–2Zn–2Er alloy including W-phase displays a better tensile strength, and the yield strength (YS) is about 247 MPa.