Decrease In Temperature Gradient Research Articles

Controlling of cellular substructure and its effect on mechanical properties of FeCoCrNiMo0.2 high entropy alloy fabricated by selective laser melting

Fine cellular substructures are typical microstructure feature of high entropy alloys (HEAs) produced via selective laser melting (SLM), playing a pivotal role in improving the mechanical properties. Nonetheless, the controlling of cellular substructure and its impact on the mechanical properties remains ambiguous. This study investigates the effect of energy densities on the cellular substructure evolution and mechanical properties of the FeCoCrNiMo0.2 HEA. It is found the increase in energy density causes a decrease in temperature gradient (G) and solidification rate (R) in molten pool, consequently leading to the increase of cellular substructure size and the intensification of Mo segregation at cellular substructure boundaries. The cellular substructure size (d) can be described by formula d=80(GR)−1/3, in which G and R can be obtained from discrete element method - computational fluid dynamics (DEM-CFD) simulation. The strength of the FeCoCrNiMo0.2 HEA is significantly affected by dislocation strengthening (σd) and segregation strengthening (σs), which are further determined by the cellular substructure size and the Mo segregation, respectively. The increase of cellular substructure size leads to the decrease of σd, while the intensification of Mo segregation results in the increase of σs. The competition between these two strengthening effects leads to an optimized and excellent tensile property of 707 MPa in yield strength, 947 MPa in ultimate tensile strength and 34 % in fracture elongation at a moderate energy density of 47 J/mm3. The findings provide guidance towards the advancement of high-performance high entropy alloys fabricated by SLM in terms of cellular substructure controlling.

Nitrate denitrification rate response to temperature gradient change during river bank infiltration.

Nitrate attenuation during river bank infiltration is the key process for reducing nitrogen pollution. Temperature is considered to be an important factor affecting nitrate attenuation. However, the magnitude and mechanism of its impact have not been clear for a long time. In this study, the effects of temperature and temperature gradient on the nitrate denitrification rate were investigated via static batch and dynamic soil column simulation experiments. The results showed that temperature had a significant effect on the denitrification rate. Temperature effects were first observed in denitrifying bacteria. At low temperatures, the microorganism diversity was low, resulting in a lower denitrification rate constant. The static experimental results showed that the denitrification rate at 19°C was approximately 2.4 times that at 10°C. The dynamic soil column experiment established an exponential positive correlation between the nitrate denitrification decay kinetic constant and temperature. The affinity of denitrifying enzymes for nitrate in the reaction substrate was ordered as follows: decreasing temperature gradient (30°C → 10°C) > zero temperature gradient (10°C) > increasing temperature gradient condition (0°C → 10°C). This study provides a theoretical basis for the biogeochemical processes underlying river bank infiltration, which will help aid in the development and utilization of groundwater resources.

Elucidating the promoting mechanism of nitrogen in the columnar-to-equiaxed transition of steel ingot

Based on the behavior of heat and mass transfer ahead of the advancing columnar front, combined with the nucleation and growth of dendrites, as well as the blocking mechanism of columnar-to-equiaxed transition (CET), the promoting mechanism of nitrogen in the CET of steel ingot was elucidated. It was found that the CET moves from the center to the edge of the ingot as the nitrogen content increases, resulting in a decrease in the columnar dendrite zone and an increase in the equiaxed dendrite zone. The occurrence of this phenomenon can be attributed to two factors. On the one hand, an increase in nitrogen content leads to an increase in critical nucleation supercooling and incubation time of dendrites, causing a decrease in the number of dendrites nucleation. Additionally, the higher nitrogen content reduces the restriction effect of solute on the growth of columnar dendrites, leading to an increase in dendrite size. On the other hand, within the constitutional supercooling (CS) zone ahead of the advancing columnar front, both the CS and temperature gradient decrease with increasing nitrogen content, while the CS increases and the temperature gradient decreases with the distance from the advancing columnar front. Consequently, the nitrogen solute primarily influences the nucleation and growth of columnar and equiaxed dendrites, as well as the length, temperature gradient, and growth restriction factor Qc of the CS zone, resulting in changes in the heat and mass transfer behavior ahead of the advancing columnar front, thereby promoting CET.

Arctic cyclones have become more intense and longer-lived over the past seven decades

Intense cyclones driving extreme Arctic weather and climate events have been more frequently observed during recent years, causing dramatic environmental and socioeconomic impacts. However, inconsistencies have emerged about long-term changes in Arctic cyclone activity. Here we analyze multiple reanalysis datasets covering a multidecadal period with improvements to the cyclone tracking algorithm and the integrated cyclone activity metric. The results indicate an intensification of Arctic cyclone activity over the last seven decades. There has been a long-term shift of the maximum cyclone counts from weaker to stronger cyclones and a pronounced lengthening of the duration of strong cyclones. Spatial analysis shows increased strong cyclone frequency over the Arctic, driven by enhanced lower troposphere baroclinicity, amplified winter jet stream waves over the subpolar North Atlantic, and a strengthened summer tropospheric vortex over the central Arctic. The stratospheric vortex has also intensified the tropospheric waves and vortex with distinct dynamics between winter and summer. Recently enhanced baroclinicity over large areas of the Arctic and midlatitudes suggests more complicated atmospheric dynamics than what is hypothesized with Arctic-amplification-induced decrease in meridional temperature gradients.

Effect of WC Content on the Wear and Corrosion Properties of Oscillating Laser-Cladding-Produced Nickel-Based Coating

Pneumatic conveying pipe is an important part of the coal industry. Its working environment is harsh, and it is mainly affected by serious wear and corrosion, which affects its operating life. Studying a method of strengthening the pipe wall of pneumatic conveying pipe is of great significance. In this paper, nickel-based alloy coatings with different WC (tungsten carbide) contents were prepared using an oscillating laser-cladding process, and the micro-characterization characteristics, wear resistance and corrosion resistance of the laser-cladded layer were discussed. The main conclusions are as follows: The microstructure of the laser-cladded layer gradually grows from the plane crystals and cellular crystals at the bottom to the relatively coarse columnar crystals in the middle, and finally to a large number of equiaxed crystals in the upper part. Moreover, with an increase in WC content, more fine equiaxed crystals are formed, mainly due to the decrease in temperature gradient with the increase in distance from the fusion line. Also, with an increase in WC content, the hardness and wear resistance of the nickel-based alloy are improved. When 20% WC is added, the laser-cladded layer shows the best corrosion resistance in 3.5 wt.% NaCl solution, and its polarization resistance is 16% lower than that when 10% WC is added. This study provides a technical reference for improving the operating life of pneumatic conveying pipelines.

Effect of the Solidification Mode on the Pore Growth of Gasar Porous Mg‐Ag Alloy

AbstractGasar porous Mg–3 wt% Ag alloy is prepared by metal–gas eutectic directional solidification process. The pore structure is related to the solidification mode of the alloy. The pores grow stably under the solidification conditions of planar, cellular, and columnar dendrites but not under the condition of equiaxed dendrites. The numerical simulation shows that the solidification velocity and temperature gradient decrease rapidly with an increase in the sample height, but their ratio remains unchanged. During the solidification process, the solidification mode of the alloy changes from cellular crystals to columnar dendrites, and finally to equiaxed dendrites. The calculated results of the solidification mode transition are consistent with the microstructure morphologies of the Mg–Ag alloy at different heights.

Horizontal Distribution of Temperature Effect in Rubberized Concrete Pavement: A Case Study

Temperature distribution and the deformation behavior under temperature are important parameters in the design and evaluation of concrete pavements. In this paper, in order to study the horizontal distribution of the temperature effect on rubberized concrete pavement (RCP), the distribution differences of temperature, temperature gradient and strain at different horizontal locations were analyzed based on fiber Bragg grating test technology. The relationships between temperature and strain and between temperature gradient and strain were also investigated. The results show that within a cycle of temperature or temperature gradient change, the time of temperature increase or temperature gradient increase is only 1/4 of the whole cycle, significantly less than the time of the temperature or temperature gradient decrease. Comparing the center, edges and corner of the pavement, the horizontal distribution of temperature and temperature gradients in the RCP is uneven, and the greatest negative temperature gradient is experienced at the corner of the pavement, which is 25 °C·m−1 greater than the temperature gradient at the center. The negative temperature gradient at the corner of the concrete pavement exacerbates the bottom deformation at the center and edge of the pavement, especially in the X-axis direction at the center and in the Y-axis and Z-axis directions at the edge. The relationships between temperature and horizontal strain at the center and edge of the RCP have a significant hysteresis effect and are markedly stronger than those at the corner. Moreover, when the temperature gradient is less than −23.4 °C·m−1 or greater than 14.5 °C·m−1, the curling effect at the edge of the RCP is more obvious.

Study on divertor detachment and pedestal characteristics in the DIII-D upper closed divertor

Experiments performed in DIII-D demonstrate that higher plasma current and heating power combined with impurity seeding facilitate the achievement of divertor detachment with a higher pedestal pressure and higher plasma performance in H-mode plasmas with a baffled closed divertor compared with an open divertor. Dedicated experiments were carried out to study the impact of power, plasma current and impurity seeding on divertor detachment with ion directed into the divertor favorable for the L–H transition. With a factor of three variation in heating power and with only D2 puffing, no significant difference in the separatrix density at detachment onset was found. The higher heating power leads to higher impurity concentration and wider scrape-off layer (SOL) width, and reduces the detachment onset density to one similar to that in lower-power plasmas. Higher current requires higher pedestal and line-averaged densities to achieve divertor detachment; however, the increase in separatrix density at increasing plasma current is found to be less pronounced. Initial calculations found that both power scan and plasma current scan datasets are qualitatively consistent with theory after considering the change in impurity concentration and heat flux width. This also motivates the future extensive study of transport and divertor impurity behavior in order to have a quantitative comparison between experiment and theory. Compared with an open divertor, a closed divertor facilitates detachment onset at ∼40% lower line-averaged plasma density. Additional N2 seeding facilitates the achievement of detachment at a lower separatrix density and thus a higher pedestal temperature, which is beneficial for advanced tokamak scenarios. Higher heating power requires a higher N2 puffing rate to achieve the same degree of detachment, while a higher N2 puffing rate leads to lower detachment onset line-averaged density, both of which agree with theory. In contrast to the narrower pedestal in an open divertor approaching detachment, the pedestal density width in a closed divertor increases with density. The density gradient increases with line-averaged density at higher plasma current, but remains nearly unchanged at lower plasma current. In particular, compared with discharges with low power, at high heating power the pedestal density gradient is much weaker, while the SOL density is significantly higher and wider. At the same plasma current, both pedestal pressure gradient and temperature gradient decrease linearly with the line-averaged density but remain similar across different heating powers. Even with different plasma current and heating power, the normalized pressure gradient remains identical. As a result, achievement of divertor detachment with a higher pedestal pressure and higher plasma performance is shown in a closed divertor, which is important for improving core–edge integration as one of the critical issues for future tokamak fusion reactors.

Effect of microsegregation behaviors on solidification microstructure of IC10 superalloy fabricated by directed energy deposition

Due to the solidification process and thermal history, the microstructure and properties along the deposition direction are generally inhomogeneous in components fabricated by the directed energy deposition technique. By developing a microsegregation model, this study gives an innovative understanding of the elemental segregation behavior of an as-deposited IC10 superalloy along the different heights and its influence on the microstructure. Results indicate that the γ-γ ´ eutectic-free microstructure is only obtained at the initial deposition layer, and as the deposition height increases, eutectic phases gradually appear in interdendritic regions. By taking account of the nonequilibrium solidification and dendritic tip undercooling, the new microsegregation model can well explain the segregation behavior of the alloy at different deposition heights. Compared to the back diffusion coefficient, the partition coefficient plays a major role in microsegregation behavior under rapid solidification conditions, especially for the elements with a high diffusion coefficient in solid, such as Ti and Al. Moreover, microstructure transformation is dependent on varying solidification processes due to the change in microsegregation. Limited by the heat transfer efficiency as the increased deposition heights, the temperature gradient and solidification rate decrease, which exacerbates the enrichment of Al and Ti at interdendritic regions and promotes the eutectic phase nucleation. Restricted by the diffusion rate of alloying elements, the eutectic reaction rate slows down, γ and γ ´ lamellae thickness increase, and finally the petal-like eutectic phases form.

A New Food Ingredient Rich in Bioaccessible (Poly)Phenols (and Glucosinolates) Obtained from Stabilized Broccoli Stalks.

Broccoli (Brassica oleracea var. italica) stalks account for up to 35% of the broccoli harvest remains with the concomitant generation of unused waste that needs recovery to contribute to the sustainability of the system. However, due to its phytochemical composition, rich in bioactive (poly)phenols and glucosinolates, as well as other nutrients, the development of valorization alternatives as a source of functional ingredients must be considered. In this situation, the present work aims to develop/obtain a new ingredient rich in bioactive compounds from broccoli, stabilizing them and reducing their degradation to further guarantee a high bioaccessibility, which has also been studied. The phytochemical profile of lyophilized and thermally treated (low-temperature and descending gradient temperature treatments), together with the digested materials (simulated static in vitro digestion) were analysed by HPLC-PDA-ESI-MSn and UHPLC-3Q-MS/MS. Broccoli stalks and co-products were featured by containing phenolic compounds (mainly hydroxycinnamic acid derivatives and glycosylated flavonols) and glucosinolates. The highest content of organosulfur compounds corresponding to the cores of the broccoli stalks treated by applying a drying descendant temperature gradient (aliphatic 18.05 g/kg dw and indolic 1.61 g/kg dw, on average, while the breakdown products were more abundant in the bark ongoing low temperature drying 11.29 g/kg dw, on average). On the other hand, for phenolics, feruloylquinic, and sinapoylquinic acid derivatives of complete broccoli stalk and bark, were more abundant when applying low-temperature drying (14.48 and 28.22 g/kg dw, on average, respectively), while higher concentrations were found in the core treated with decreasing temperature gradients (9.99 and 26.26 g/kg dw, on average, respectively). When analysing the bioaccessibility of these compounds, it was found that low-temperature stabilization of the core samples provided the material with the highest content of bioactives including antioxidant phenolics (13.6 and 33.9 g/kg dw of feruloylquinic and sinapoylquinic acids, on average, respectively) and sulforaphane (4.1 g/kg dw, on average). These processing options enabled us to obtain a new product or ingredient rich in bioactive and bioaccessible compounds based on broccoli stalks with the potential for antioxidant and anti-inflammatory capacities of interest.

Elevated Temperature Baseplate Effect on Microstructure, Mechanical Properties, and Thermal Stress Evaluation by Numerical Simulation for Austenite Stainless Steel 316L Fabricated by Directed Energy Deposition

In the present study, the effect of material deposition at the elevated temperature baseplate on the microstructure and mechanical properties was investigated and correlated to the unique thermal history by using numerical simulation. Numerical results agreed well with the experimental results of microstructure and mechanical properties. Numerical results revealed a significant decrease in temperature gradient and a 40% decrease in thermal stress due to material deposition on the elevated temperature baseplate. The reduced thermal stress and temperature gradient resulted in coarser grain features, which in turn led to a decrease in hardness and tensile strength, especially for the bottom region near the baseplate. Meanwhile, no significant effect could be found for ductility. In addition, an elevated temperature baseplate promoted less heterogeneity in hardness and tensile properties along the building direction. The current work demonstrates a collective and direct understanding of the baseplate preheating effect on thermal stress, microstructure and mechanical properties and their correlations, which is believed beneficial for the better utilization of baseplate preheating positive effects.

Microstructure evolution and mechanical properties of SUS301L stainless steel sheet welded joint in ultrasonic vibration assisted laser welding

Ultrasonic assisted laser welding (ULW) is a newly developed welding method. In this paper, a new kind of ultrasonic assisted laser welding method, which is named trailing ultrasonic assisted laser welding (T-ULW) is proposed. First, the welding temperature fields as well as the weld pool temperature evolution in trailing ultrasonic assisted laser welding (T-ULW) and conventional laser welding (LW) are numerically simulated, and the shapes of the molten pools during T-ULW and LW are observed by a high-speed camera monitoring system. Both the simulation and monitoring results show that ultrasonic can reduce the temperature gradient of the weld pool and prolong the solidification time. Then, such three kinds of welding methods as T-ULW, common fixed-position ultrasonic assisted laser welding (F-ULW) and LW are used to weld SUS301 stainless steel sheet with a thickness of 0.6 mm respectively, and their performances are comparatively investigated by analyzing the experimentally-obtained macro morphologies, microstructures of welded joints. Macro morphology analysis results show that ultrasonic vibration not only elongates the molten pool, but also changes the cross-sectional shapes of the welds in such a way that decreases the top width and increases the bottom width. Microstructure analysis results indicate that the fusion zone of the welds obtained by T-ULW is uniformly distributed mainly by the refined equiaxed grains. Subsequently, the crystal refinement mechanisms of the welds in ultrasonic-assisted laser welds of SUS301 stainless steel are theoretically analyzed and experimentally verified, which show that due to ultrasonic disturbance, the temperature gradient of the molten pool is decreased, a stress field is generated in the welds and a so-called ultrasonic cavitation effect is produced in the molten pool. Such three mechanisms play very important roles in refining crystals in different ways that the decreased temperature gradient provides a good nucleation condition for the growth of equiaxed dendrite, and both the generated stress and ultrasonic cavitation cause the grain boundary to fracture, thereby form more new grain boundary, which finally lead to form fine and uniform grains in the welds. Finally, the mechanical properties of the joints are measured, and the results demonstrated that ultrasonic assisted laser welding especially T-ULW enables not only to increase the tensile strength of the welds, but also to improve the ductility of the welds.

Electrochemical Properties of Diluted Al-Mg Alloys With Columnar-To-Equiaxed Transition

The objective of the present research is to study the corrosion susceptibility of two Al-Mg diluted alloys (Al-0.5wt.%Mg and Al-2wt.%Mg) with different grains structures obtained by directional solidification (columnar, equiaxed and columnar-to-equiaxed transition, CET) in 0.5% NaCl solution, at room temperature. The corrosion resistance is analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in both longitudinal and transversal sections of the samples. The columnar grain zone presents higher corrosion resistance than the equiaxed grain zone. In addition, the transversal section shows higher corrosion resistance than the longitudinal section of the samples. Then, the Al-0.5wt.% Mg alloy displays higher corrosion resistance than the Al-2wt.% Mg alloy. The values of the polarization resistance are used as a basic criterion for the evaluation of the corrosion resistance of both alloys. In this way, when the polarization resistance decreases with the increasing in the distance from the base, the grain size, secondary dendritic arm spacings and hardness increases. In addition, when the polarization resistance increases, the critical temperature gradient decreases.

Laser printing path and its influence on molten pool configuration, microstructure and mechanical properties of laser powder bed fusion processed rare earth element modified Al-Mg alloy

ABSTRACT This work investigated the influence of laser scan strategy, which essentially determines the molten pool path, on microstructure evolution, residual stress and mechanical properties of the LPBF processed Al-4.2Mg-0.4Sc-0.2Zr alloy. Laser scan strategies including parallel, bi-directional, island and remelting modes were applied for comparison. The remelting specimen exhibited a relatively smooth surface with R a = 10.2 ± 0.9 μm combined with minimum residual stress of ϵ = 0.195, which was attributed to the decreased temperature gradient within the molten pool during the remelting process. The tensile properties for the remelting mode were decreased from 500 MPa to 473 MPa combined with elongation reduced from 15% to 7% compared to those of the other strategies. It was mainly caused by the precipitation coarsening, which further changed the strengthening mechanism from precipitate shearing to Orowan dislocation looping mechanism. This study proves that the surface roughness, residual stress and properties can be well tailored through optimising laser scan strategies.

Orientation selection of particles growing in an alloy melt

The dynamics of orientation selection of a particle in an alloy melt is studied by using the method of multiple scales. The dynamic model accounts for two sources of anisotropic interfacial energy, which is characterized by two anisotropy parameters ε1 and ε2. The anisotropy parameters and the initial concentration are systematically changed to investigate the continuous orientation variations of the growing particle. In the <100> directions, as the anisotropy parameter ε1 increases, the interface temperature and concentration gradient increase, and the interface of the particle accelerates its growth and becomes locally convex, whereas in the <110> directions, the interface temperature and concentration gradient decrease, and the interface decelerates its growth and becomes locally concave. During this growth process, the particle changes continuously its preferred growth direction from <110> to <100>. As negative ε2 increases, a reversed process occurs that the particle changes continuously its preferred growth direction from <100> to <110>. In the preferred growth direction, the initial concentration inhibits the growth of the particle, whereas in other growth directions the initial concentration facilitates the growth of the particle. The orientation selection of the particle displays the rich interface morphologies of the particle with deformed petal-shaped patterns.

Numerical modelling of electron beam welding (EBW) of Zhs6u superalloy and its experimental validation

ABSTRACT In this paper, the electron beam welding of Zhs6u superalloy is modelled numerically by a combined heat input model. Also the welding process was performed experimentally on Zhs6u samples to validate the numerical results. The results showed that weld pool shape obtained by the numerical model was in accordance to the experimental analysis of the weld cross section. Also the numerical model was able to predict the susceptibility to formation of liquation cracks in the heat-affected zone based on the study of the temperature gradient during the solidification stage. It was found that by increasing the heat input the temperature gradient decreases and it takes more time for the workpiece to solidify which decreases the susceptibility to liquation crack formation.

The influence of twin boundary on lattice thermal conductivity of thermoelectric InSb

Twin boundaries (TBs) can increase interface scattering to reduce the lattice thermal conductivity. InSb has good electronic transport properties, but its high thermal conductivity constrains its thermoelectric application. In this work, we aim to study the role of TBs on lattice thermal conductivity of InSb. We use non-equilibrium molecular dynamics simulation to investigate how the TB spacing and orientation influence the lattice thermal conductivity of InSb. We find that TBs can hinder the heat flow, leading to decreased temperature gradient and, hence, remarkably reduced lattice thermal conductivity. The relationship between κL and λ can be described by a proportional function. Nanotwinned InSb with TB spacing of 1.1 nm has a lattice thermal conductivity of 12.6 W/m K, a decrease in 22.2% compared with its single crystal (16.2 W/m K). We also find that a minimum lattice thermal conductivity of InSb can be obtained when the TB orientation is perpendicular to the direction of heat flow. These findings provide a theoretical guidance for TBs engineering to reduce the thermal conductivity of thermoelectric materials.

The Seesaw of Seasonal Precipitation Variability Between North China and the Southwest United States: A Response to Arctic Amplification

AbstractSurface albedo over the ice‐covered polar ocean is decreased in a highly idealized numerical experiment, which leads to stronger (weaker) warming at high (low) latitudes, and forms Arctic amplification. With stronger warming at both high and low latitudes, the meridional temperature gradient decreases (increases) at midlatitudes (subtropical regions). A cyclonic wind anomaly appears and results in a weak Kuroshio current and warm interdecadal Pacific Oscillation phase. In response to Arctic‐amplified‐warming, the subtropical high weakens, leading to summer monsoon anomaly on its southside and increased westward transport of water vapor, resulting in a seesaw pattern: dry (wet) conditions in summer in North China (southwest United States, SWUS). In winter, the East Asian trough (North American high) decreases and induces decreased (increased) cold air transport to North China (SWUS) in response to Arctic‐amplified‐warming, which makes rain unlikely (likely) and exhibits a seesaw pattern. Moisture convergence always appears in a warmer SWUS winter, and increases precipitation there, which strengthens (counteracts) the precipitation anomaly led by the North American high in a warm (cold) interdecadal Pacific Oscillation phase. It may even shut down the seesaw pattern in winter in the cold interdecadal Pacific Oscillation phase.

Shaping quality, microstructure, and mechanical properties of melt-grown mullite ceramics by directed laser deposition

Directed laser deposition (DLD) has demonstrated the potential for rapid preparing high-performance melt-grown ceramics applied for the aero-engine hot section components. Mullite has excellent potential for applications in harsh environments and extreme conditions. However, there are defects (pores and cracks) in melt-grown mullite ceramics (MGMC), limiting its application, related to unclear processes, microstructure, and properties. In this work, we investigated the impact of z-increment on shaping quality, microstructure, and mechanical properties. The results reveal that oxygen vacancy concentration is responsible for the variety of sample colors. Low z-increment is beneficial to decreasing porosity, while high z-increment is beneficial to crack suppression. The formation and propagation mechanism of internal cracks at low z-increment are discussed in detail. Mullite crystals in the sample center are "tabular cellular", which are 2:1 high-alumina mullite. While mullite crystals at the sample edge are 3:2 mullite, undergo four stages as z-increment increase; "tabular cellular", "facet dendrite", "rod cellular", and mixed crystal. This evolution of crystal morphology is attributed to the decrease in temperature gradient and the increase of supersaturation. Besides, the flexural strength and microhardness increase first and then decrease with the rise of z-increment, which is the function of defects, compactness, and microstructure.

Effects of thermal radiation on Eyring–Powell fluid flow and heat transfer over a power-law stretching permeable surface

The main objective of this paper is to investigate the effects of thermal radiation on Eyring–Powell fluid flowing over a power-law stretching sheet in presence of suction/blowing. Similarity transformations are used to find the self-similar form of the governing equations. It is established that for a particular value of power-law stretching velocity self-similar solutions exist for the problem. Shooting technique is applied for solving numerically the reduced ordinary differential equations. The effects of fluid parameters, suction/blowing parameter on velocity, skin friction co-efficient, temperature, and wall temperature gradient are analyzed and presented through tables and graphs as far as practicable. The effect of radiation parameter on wall temperature gradient is presented graphically. Velocity decreases with the increasing values of one of the fluid parameter and increases with increasing values of the other fluid parameter. Velocity and momentum boundary layer thickness decrease with the increasing values of suction/blowing parameter. For one fluid parameter, the absolute values of skin friction co-efficient decrease but the absolute values of temperature gradient at the wall increase. On the other hand, reverse trend is noted for other fluid parameter. The values of wall temperature gradient decrease with increasing Prandtl number and radiation parameter. Dimensionless temperature and thermal boundary layer thickness decrease with rise in Prandtl number, radiation parameter, and suction/blowing parameter.