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In 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.

The heat treatment from 1,000°C to 1,300°C was applied to SDSS to check the effect of the cooling rate.

The 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.

The effect of secondary phase not consider because that is well known to decreasing corrosion resistance.

Solution 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.

Manufacturers need to know the effect of the cooling rate to optimize the corrosion resistance, and this study can be applied in the industrial scene.

SDSS 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.

Detailed studies to characterise the coarsening behaviour of eutectic Sn‐Ag and near‐eutectic Sn‐Pb‐Ag solder joints were carried out on samples reflow soldered and solidified at various cooling rates. Light and scanning electron microscopy as well as EDS were used to study the microstructural evolution, while microhardness measurements were used to monitor the change in the mechanical properties. Samples consisting of copper substrates and solder paste were reflow soldered about 30 °C above their melting points and then solidified at cooling rates ranging from furnace cooling to rates associated with water quenching. Analysis of some of these samples showed that increasing the cooling rate increased the quantity (volume fraction) of primary Sn‐dendrites, decreased the (EQ) intermetallic phase in the bulk solder, and resulted in finer microstructures with higher hardness. The microstructural evaluation involved characterisation of bulk intermetallica and dendrite/eutectic ratios. Subsequent isothermal annealing of these reflow soldered joints at 125 °C for times between 0.25 h and 8 days resulted in an initially fairly rapid decrease in hardness to a given level for each alloy and each cooling rate.

Accurate prediction of residual stress requires precise knowledge of the constitutive behavior of as-quenched material. This study aims to model the flow stress behavior for as-quenched Al-Mg-Si alloy.

In the present work, the flow behavior of as-quenched Al-Mg-Si alloy is studied by the hot compression tests at various temperatures (573–723 K), strain rates (0.1–1 s⁻¹) and cooling rates (1–10 K/s). Flow stress behavior is then experimentally observed, and an Arrhenius model is used to predict the flow behavior. However, due to the fact that materials parameters and activation energy do not remain constant, the Arrhenius model has an unsatisfied prediction for the flow behavior. Considering the effects of temperatures, strain rates and cooling rates on constitutive behavior, a revised Arrhenius model is developed to describe the flow stress behavior.

The experimental results show that the flow stress increases by the increasing cooling rate, increasing strain state and decreasing temperature. In comparison to the experimental data, the revised Arrhenius model has an excellent prediction for as-quenched Al-Mg-Si alloy.

With the revised Arrhenius model, the flow behaviors at different quenching conditions can be obtained, which is an essential step to the residual stress prediction when the model is implemented in a finite element code, e.g. ABAQUS, in the future.

This study aims to focus on numerical simulation investigations of phase transformation during cooling of 55SiMnMo steel, which is commonly applied to improve mechanical properties.

A mathematical model based on the finite element method (FEM) and the phase transformation kinetics model has been proposed to predict microstructure changes during continuous cooling of 55SiMnMo steel. This model can be employed to analyze the variation of austenite, special upper bainite and lump-like composite structure with cooling time at different cooling rates.

According to the continuous cooling experiments, when the cooling rate is lower than 0.1°C/s, the special upper bainite is the only transformation product which decreases with increasing cooling rate; when the cooling rate is above 0.5°C/s, the transformation products include special upper bainite and lump-like composite structure. Meanwhile, the results of continuous cooling experiment verified the correctness of this finite element model.

This model has a great value for proper controlling of the cooling process which can improve the quality of hollow drill steel and increase the service life of the final product.

This study aims to investigate the effect of mechanical peening on the cooling rate of a subsequently deposited layer in a hybrid additive manufacturing (AM) process.

In this experimental study, 20 layers of 316 L stainless steel are built via directed energy deposition, with the tenth layer being subject to various peening processes (shot peening, hammer peening and laser shock peening). The microstructure of the eleventh layer of all the samples is then characterized to estimate the cooling rate.

The measurements indicate that the application of interlayer peening causes a reduction in primary cellular arm spacing and an increase in micro segregation as compared to a sample prepared without interlayer peening. Both factors indicate an increase in the cooling rate brought about by the interlayer peening.

This work provides insight into process design for hybrid AM processes as cooling rates are known to influence mechanical properties in laser-based AM.

To the best of the authors’ knowledge, this work is the first of its kind to evaluate the effects of interlayer peening on a subsequently deposited layer in a hybrid AM process.

Currently, human hearts destined for transplantation can be used for 4.5 hours which is often insufficient to test the heart, the purpose of this paper is to find a compatible recipient and transport the heart to larger distances. Cooling systems with simultaneous internal and external liquid cooling were numerically simulated as a method to extend the usable life of human hearts.

Coolant was pumped inside major veins and through the cardiac chambers and also between the heart and cooling container walls. In Case 1, two inlets and two outlets on the container walls steadily circulated the coolant. In the Case 2, an additional inlet was specified on the container wall thus creating a steady jet impinging one of the thickest parts of the heart. Laminar internal flow and turbulent external flow were used in both cases. Unsteady periodic inlet velocities at two frequencies were applied in Case 3 and Case 4 that had four inlets and four outlets on walls with turbulent flows used for internal and external circulations.

Computational results show that the proposed cooling systems are able to reduce the heart temperature from +37°C to almost uniform +5°C within 25 min of cooling, thus reducing its metabolic rate of decay by 95 percent. Calculated combined thermal and hydrodynamic stresses were below the allowable threshold. Unsteady flows did not make any noticeable difference in the speed of cooling and uniformity of temperature field.

This is the pioneering numerical study of conjugate convective cooling schemes capable of cooling organs much faster and more uniformly than currently practiced.

The current investigation aims at observing the influence of the cooling channel on the thermal and residual stress behavior of the selective laser melting (SLM)316L uni-layer thermo-mechanical model.

On a thermo-mechanical model with a cooling channel, the effect of scanning direction, parallel and perpendicular and scan spacing was simulated. The effect of underlying solid and powder bases was evaluated on residual stress profile and thermal variables at various locations.

The high heat dissipation of solid base due to high cooling rates and steep thermal gradients can reciprocate with smaller melt pool temperature and melt pool size. Given the same scan spacing, residual stresses were found lower when laser scanning was perpendicular to the cooling channel. Moreover, large scan spacing was found to increase residual stresses.

Cooling channels are increasingly being used in additive manufacturing; however, their effect on the residual stress behavior of the SLM component is not extensively studied. This research can serve as a foundation for further inquiries into the impact of base material design such as cooling channels on manufactured components using SLM.

The aim of this research is to study the influence of laser additive manufacturing process parameters on the deposit formation characteristics of Inconel 718 superalloy, the main parameters that influence the forming characteristics, the cooling rate and the microstructure were studied.

Orthogonal experiment design method was used to obtain different deposit shape and microstructure using different process parameters by multiple layers deposition. The relationship between the processing parameters and the geometry of the cladding was analyzed, and the dominant parameters that influenced the cladding width and height were identified. The cooling rates of different forming conditions were obtained by the secondary dendrite arm spacing (SDAS).

The microstructure showed different characteristics at different parts of the deposit. Cooling rate of different samples were obtained and compared by using the SDAS, and the influence of the process parameters to the cooling rate was analyzed. Finally, micro-hardness tests were done, and the results were found to be in accordance with the micro-structure distribution.

Relationships between processing parameters and the forming characteristics and the cooling rates were obtained. The results obtained in this paper will help to understand the relationship between the process parameters and the forming quality of the additive manufacturing process, so as to obtain the desired forming quality by appropriate parameters.

This paper aims to investigate the possibilities and determination of hot and warm forging of ultrahigh-strength steel 300M and subsequent quenching with accelerated air. Analysis of microstructure and mechanical properties of forged steel 300M focused on investigation of the effect of processing conditions on final properties, such as strength, impact strength and hardness, taking into consideration temperature gradients and within-part strain nonuniformity occurring in forging and direct cooling of aircraft landing gear.

The research involved semi-industrial physical modeling of hot deformation and direct cooling, aided with numerical analysis of both deformation and kinetics of phase transformations on cooling, with process conditions determined on the basis of numerical simulation of industrial process. Examination of forged and quench-tempered samples involved testing mechanical properties (tensile properties, hardness and impact strength) and microstructure.

Three major findings were arrived at: first, assessment of the effects of energy-saving method of cooling conducted directly after forging. Second, tensile properties, hardness and impact strength, were analyzed on the background of microstructure evolution during hot-forging and direct cooling; hence, applied temperature and cooling rates refer to actual condition of the material including varied deformation history. Third, the accelerated air cooling tests were carried out directly after forging with accurately measured and described cooling efficiency, which enabled the acquisition of data for heat treatment simulation with use of untypical cooling media.

The conclusions formulated on the strenght of studies carried out in semi-industrial conditions with the use of model samples, despite strain and strain rate similarity, wait for full-scale verification in industrial conditions. The direct cooling tests carried out in semi-industrial conveyor Quenchtube are of cognitive value. Industrial realization of the process for the analyzed part calls for special construction of the cooling line and provision of higher cooling rate for heavy sections.

The results present microstructure properties’ relations for good-hardenability grade of steel, which is representative of several similar grades used in aircraft industry, which can support design of heat treatment (HT) cycles for similar parts, regardless of whether direct or conventional quenching is used. As they illustrate as-forged and direct-cooled microstructure and resultant mechanical properties, the studies concerning processing the steel of areas of lower temperature are transferable to warm forging processes of medium-carbon alloy steels. The geometry of the part analyzed in the case study is typical of landing gear of many aircrafts; hence, there is the high utility of the results and conclusions.

The direct heat treatment technologies based on utilization of the heat attained in the part after forging allow significant energy savings, which besides cost-effectiveness go along with ecological considerations, especially in the light of CO₂ emission reduction, improving economical balance and competitiveness. The presented results may encourage forgers to use direct cooling, making use of the heat attained in metal after hot forging, for applications to promote environmentally friendly heat treatment-related technologies.

Direct heat treatment typically seems to be reserved for micro alloyed steel grades and sections small enough for sufficient cooling rates. In this light, taking advantage of the heat attained in forged part for energy-saving method of cooling based on direct quenching as an alternative to traditional Q&T treatment used with application to relatively heavy sections is not common. Moreover, in case the warm-work range is reached in any portion of the forged part, effect of direct cooling on warm-forged material is addressed, which is a unique issue to be found in the related studies, whereas in addition to warm forging processes, the results can be transferable to coining, sizing or shot peening operations, where gradient of properties is expected.

The purpose of this paper is to investigate the morphology of intermetallic (IMC) compounds and the mechanical properties of SAC305 solder alloy under different cooling conditions.

SAC305 solder joints were prepared under different cooling conditions/rates. The performance of three different etching methods was investigated: simple chemical etching, deep etching based on the Jackson method and selective removal of β-Sn by a standard three-electrode cell method. Phase and structural analyses were conducted by X-ray diffraction (XRD). The morphology of etched solder was examined by a field emission scanning electron microscope. The hardness evaluations of the solder joints were conducted by a Vickers microhardness tester.

The Ag₃Sn network was significantly refined by the ice-quenching process. Further, the thickness of the Cu₆Sn₅ layer decreased with an increase in the cooling rate. The finer Ag₃Sn network and the thinner Cu₆Sn₅ IMC layer were the results of the reduced solidification time. The ice-quenched solder joints showed the highest hardness values because of the refinement of the Ag₃Sn and Cu₆Sn₅ phases.

The reduction in the XRD peak intensities showed the influence of the cooling condition on the formation of the different phases. The micrographs prepared by electrochemical etching revealed better observations regarding the shape and texture of the IMC phases than those prepared by the conventional etching method. The lower grain orientation sensitivity of the electrochemical etching method (unlike chemical etching) significantly improved the micrographs and enabled accurate observation of IMC phases.