Cooling Slope Research Articles

Modeling and Prediction of The Mechanical Properties of Feedstock by Cooling-Slope Casting Process using MOJaya Algorithm

Cooling-slope (CS) casting parameters optimization is very challenging due to the uncertainties of parameter values that are influenced by many factors. Therefore, a combination of estimation and optimization models that can solve multi-objective problems using limited data is proposed to reduce the real casting operational cost and time. In casting optimization, modeling and optimization of CS parameters have been considered to identify optimal CS parameters that would lead to better feedstock performance. Computational techniques have been suggested by previous researchers to solve the optimization in the manufacturing process. The study assessed the CS process to determine the feedstock's quality by evaluating its mechanical qualities, namely Tensile strength and Impact strength. Hence, computational methods namely the MOJaya algorithm are utilized to model and optimize the parameters of CS to address the CS problem and forecast the performance of the feedstock. This work conducted a thorough analysis of the impact of CS process parameters on the tensile strength and impact strength using an experimental design. The experiment was conducted using a three-level full factorial design (FFD) of the experiment (DOE), for the parameters of pouring temperature, slanting angle, and pouring distance. The modeling technique involved the development of multiple polynomial regression (MPR) as an objective function in the MOJaya Algorithm. The outcome of the optimization procedure revealed that the optimal solutions obtained from MOJaya were projected to surpass both the initial experimental data and the MOJaya algorithm in terms of the highest values of tensile strength and impact strength. The difference between the two sets of values is 10.92% and 15.76%, respectively. Subsequently, this technique may be employed by a caster to forecast the performance of the feedstock without using repeated experiments that are costly and time-consuming.

Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands.

Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional-scale and local-scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one-season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional-scale and local-scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot-level variation was contingent on pasture-level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture-level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture-level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot-level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture-level and plot-level favorability interacted: perennial grasses had a higher plot-level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross-scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.

Modelling and Optimisation of Cooling-slope Parameters of Magnesium AZ91D using Improvement Multi-Objective Jaya Approach for Predicted Feedstock Performance

The cooling-slope (CS) casting technique is one of the simple semi-solid processing (SSP) processes a foundryman uses to produce the feedstock. This study attempts to develop mathematical regression models and optimise the CS parameters process for predicting optimal feedstock performance, which utilises tensile strength and impact strength to reduce the number of experimental runs and material wastage. This study considers several parameters, including pouring temperature, pouring distance, and slanting angles for producing quality feedstock. Hence, multi-objective optimisation (MOO) techniques using computational approaches utilised alongside the caster while deciding to design are applied to help produce faster and more accurate output. The experiment was performed based on the full factorial design (FFD). Then, mathematical regression models were developed from the data obtained and implemented as an objective function equation in the MOO optimisation process. In this study, MOO named multi-objective Jaya (MOJaya) was improved in terms of hybrid MOJaya and inertia weight with archive K-Nearest Neighbor (MOiJaya-aKNN) algorithm. The proposed algorithm was improved in terms of the search process and archive selection to achieve a better feedstock performance through the CS. The study’s findings showed that the values of tensile and impact strengths from MOiJaya_aKNN are close to the experiment values. The results show that the hybrid MOJaya has improved the prediction of feedstock using optimal CS parameters.

Regression model based properties prediction of A356 aluminum alloy rheocast using cooling slope technique

The current research work involves experimental research of the Al-alloy rheocasting with enhanced microstructural and mechanical characteristics after using the Semi-Solid Metal (SSM) processing method, which is the cooling slope method. The studies here were carried out online with Central Composite Design (CCD) in order to create a non-linear regression model to represent the fabrication of A356 casting considering the Cooling Slope (CS) Technique. During the rheocasting, the angle as well as the length of the slope, along with nozzle height were taken as the input process parameters, whereas the microhardness, grain size, and sphericity of the sample were treated as the responses. The variation of such responses across the cross-section of the casting was measured at three different locations such as the center, mean, and outer radii. The non-linear regression techniques applied to the A356 sample were manufactured under two circumstances, such as ‘with’ and ‘without’ isothermal treatment. The regression models thus developed were validated by incorporating Analysis of the Variance (ANOVA). Further, the correctness of the regression representations was verified through ten experimental test samples. The percentage deviation of experimental outcomes from the model-predicted outputs was minimal. The developed mathematical models were representative of the physical process with reasonably good accuracy.

Experimental Study and Optimization of Process Parameters for Producing Semi-Solid A392 Alloy Using Vibration-Assisted Cooling Slope Process Integrated with Mould Vibration

Experimental Study and Optimization of Process Parameters for Producing Semi-Solid A392 Alloy Using Vibration-Assisted Cooling Slope Process Integrated with Mould Vibration

Effect of Melt Treatment on Microstructure Evolution and Coarsening Mechanism of A356 Al Alloy During Cooling Slope Rheoprocessing

Effect of Melt Treatment on Microstructure Evolution and Coarsening Mechanism of A356 Al Alloy During Cooling Slope Rheoprocessing

Microstructure Evolution During Rheoprocessing of A356 Al Alloy Using Cooling Slope

Microstructure Evolution During Rheoprocessing of A356 Al Alloy Using Cooling Slope

Impact of Coolant Water Flow Rate and Temperature Underside Cooling Slope on Solidification with Microstructure and Mechanical Properties of Casted AZ91 Mg Alloy

Impact of Coolant Water Flow Rate and Temperature Underside Cooling Slope on Solidification with Microstructure and Mechanical Properties of Casted AZ91 Mg Alloy

Microstructure and Mechanical Properties of an In Situ Al 356-Mg2Si-TiB2 Hybrid Composite Prepared by Stir and Cooling Slope Casting

Microstructure and Mechanical Properties of an In Situ Al 356-Mg2Si-TiB2 Hybrid Composite Prepared by Stir and Cooling Slope Casting

Jaya Algorithm for Optimization of Cooling Slope Casting Process Parameters

This study proposed the Jaya algorithm to estimate an improved value of billet performance through the cooling casting process. Jaya algorithm is a recent evolution-based algorithm that simulates using stochastic behaviour. The algorithm concept is the solution obtained for a given problem should move towards the best solution and should avoid the worst solution. This algorithm requires only the common control parameters and does not require any algorithm specific control parameters. To the best our knowledge, Jaya algorithm is not yet been used computational approach for optimization practice, particularly in the Cooling casting process. Three Cooling slope parameters process that influences the billet performance measurements, a maximum degree of sphericity and minimum grain size are pouring temperature, slanting angle, and travelling distance. The results show that the Jaya algorithm gave a better optimal solution for the maximum degree of sphericity and minimum particle size than experimental data.

Investigation of Simultaneous Effects of Cooling Slope Casting and Mold Vibration on Mechanical and Microstructural Properties of A356 Aluminum Alloy

Investigation of Simultaneous Effects of Cooling Slope Casting and Mold Vibration on Mechanical and Microstructural Properties of A356 Aluminum Alloy

Effect of Cooling Slope Process Parameters on Non-dendritic Feedstock Production: A Comprehensive Review

Semi-solid metal processing is the well-known technique used for the production of Al-based alloys components with sound quality and improved properties. To produce and operate successfully, the microstructure of the molten metal at the entry point of the die should consist of a solid, non-dendrite, near-globular primary grains surrounded by a liquid matrix. In the present paper, the authors have made an attempt to present a review on the formation of non-dendrite particles through cooling slope (CS) technique and reported the effect of various process parameters in particular, cooling slope length, degree of superheat of metal, height and diameter of the nozzle, CS plate material, mold material and its temperature, coolant type, coolant temperature and flow rate on the microstructure of the fabricated alloy system.

Globularization of Primary Phase of Al–7Si–0.3Mg Alloy During Cooling Slope Processing and Isothermal Holding

This study is aimed towards process design for semi-solid slurry generation of Al–7Si–0.3Mg alloy using cooling slope as a slurry maker, and subsequent isothermal holding to promote globularization of slurry microstructure. The study primarily reports globularization mechanism of cooling slope processed semi-solid slurry of the alloy, and efforts are directed to establish process control by investigating the effect of coarsening during isothermal holding on the shape, size and distribution of primary Al grains. As an outcome of this study, we propose a modified Lifshitz–Slyozov Wagner equation to quantify the effect of coarsening mechanisms prevailing during isothermal holding of the said alloy slurry. The evolution of primary phase morphology due to addition of grain refiner has also been studied and ideal processing condition is identified for the end goal of component development through rheo pressure die casting route.

Semi Solid Casting of Aluminum Alloy Using a Cooling Slope Technic.

Semi Solid Casting of Aluminum Alloy Using a Cooling Slope Technic.

Cooling slope casting of AA7075 alloy combined with reheating and thixoforging

Abstract Cooling slope casting has been applied to aluminium casting alloys for producing ingots with non-dendritic microstructure. Semi-solid forming of the AA7075 was studied via cooling slope casting, reheating and thixoforging processes in order to determine the effect of semi-solid casting on the microstructure of the alloy. AA7075 ingots with non-dendritic microstructure were produced with cooling slope pouring. Castings were characterized by light microscopy, image analysis, scanning electron microscopy and EDS analysis. The resulting structures are promising in terms of grain size and sphericity. It was realized that grain coarsening may occur very suddenly in the reheating process. Cooling slope castings were obtained with 30° and 60° inclination angles, and in comparison, 60° castings showed better results. Moreover, by using short reheating periods, semi-solid forging causes trace formation in the solid grains.

Kesan Proses Pembentukan Tuangan Reo terhadap Sifat Mikrostruktur dan Mekanikal Aloi Al-5.7Si-2Cu-0.3Mg

This study shows the results of an experimental investigation of semisolid rheocasting of Al-5.7Si-2Cu-0.3Mg alloy using a cooling slope (CS) casting technique. However, the challenge is to determine process parameters of the CS process to get a desirable microstructure in the semisolid feedstock material. cooling slope technique was employed to create feedstock material for thixoforming under an argon gas atmosphere, where on an inclined plate that was fixed at a 60° slope angle, molten alloy is poured at different temperatures of 640°C, 650°C and 660°C at lengths 300, 400 and 500 mm. Examination the microstructure with optical microscope observed that the microstructure of conventionally cast alloy presented coarse and dendritic primary α-Al phase, whereas rheocast alloy included fine and nondendritic primary α-Al phase with homogeneous distribution of eutectic phase. The best CS processing condition has been identified for optimum pouring temperature of 650°C and the slope length of 400 mm as average globular grain size of around 31.67 ± 3 μm and a shape factor of about 0.66 ± 0.09 were obtained. The mechanical properties of conventional cast alloy were enhanced by the CS casting process. The ultimate tensile strength, the yield strength and elongation of the rheocast alloy were increased by 10%, 12% and 22% respectively compared to the conventional cast alloy. due to a reduction in shrinkage and porosity of the microstructure of the CS alloy.

Microstructural Development of Aluminum A201 Alloy Semi-Solid Processing Feedstock Produced by Different Routes

Thixoforming or Semi-Solid Metal (SSM) forming is a manufacturing route that relies on a non-dendritic microstructure, a structure that is retained after processing resulting in components of fine and uniform microstructures with enhanced mechanical properties as compared to conventional cast products. In this project, an investigation is conducted on the microstructural development of Aluminium A201 alloy in the semi-solid range, through a combination of variable time and temperature conditions. Using equilibrium and non-equilibrium (Scheil) curves, the solidus and the liquidus temperatures as well as the melting behaviour of this alloy are estimated. The temperature range for the thixoforming process typically lies within the 40-60% fraction liquid and this is found to be between 620oC to 637oC for this particular alloy. The aim is to heat treat specimens of this alloy within the semi-solid range (the process window) and observe the resulting microstructures to establish if they comprise of near-spheroidal solid phase particles surrounded by a liquid phase. This microstructure gives the material its thixotropic properties; i.e. the material flows like a liquid when sheared but thickens and behaves like a solid when it is allowed to stand. Three different routes for obtaining the non-dendritic microstructure necessary for thixoforming are investigated in this work: Magneto-Hydrodynamic (MHD) stirring, Strain Induced Melt Activated (SIMA) and Semi-Solid Rheocasting via Cooling Slope (SSR+CS) route. These routes are compared and their potential for future thixoforming applications studied.

Microstructure and Properties of Semi-solid ZCuSn10P1 Alloy Processed with an Enclosed Cooling Slope Channel

Semi-solid ZCuSn10P1 alloy slurry was fabricated by a novel enclosed cooling slope channel (ECSC). The influence of pouring length of ECSC on the microstructures of ZCuSn10P1 alloy semi-solid slurry was studied with an optical microscope an optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Liquid squeeze casting and semi-solid squeeze casting were performed under the same forming conditions, and the microstructure and properties were compared. The results show that primary α-Cu phase gradually evolved from dendrites to worm-like or equiaxed grains under the chilling action of the inner wall of the ECSC. The mass fraction of tin in the primary α-Cu phase increased from 5.85 to 6.46 after the ECSC process, and intergranular segregation was effectively suppressed. The finest microstructure can be obtained at 300 mm pouring length of ECSC; the equivalent diameter is 46.6 μm and its shape factor is 0.73. The average ultimate tensile strength and average elongation of semi-solid squeeze casting ZCuSn10P1 alloy reached 417 MPa and 12.6%, which were improved by 22% and 93%, respectively, as compared to that of liquid squeeze casting.

Multiphase Model of Semisolid Slurry Generation and Isothermal Holding During Cooling Slope Rheoprocessing of A356 Al Alloy

In the present paper, we present an experimentally validated 3D multiphase and multiscale solidification model to understand the transport processes involved during slurry generation with a cooling slope. In this process, superheated liquid alloy is poured at the top of the cooling slope and allowed to flow along the slope under the influence of gravity. As the melt flows down the slope, it progressively loses its superheat, starts solidifying at the melt/slope interface with formation of solid crystals, and eventually exits the slope as semisolid slurry. In the present simulation, the three phases considered are the parent melt as the primary phase, and the solid grains and air as secondary phases. The air phase forms a definable air/liquid melt interface as the free surface. After exiting the slope, the slurry fills an isothermal holding bath maintained at the slope exit temperature, which promotes further globularization of microstructure. The outcomes of the present model include prediction of volume fractions of the three different phases considered, grain evolution, grain growth, size, sphericity and distribution of solid grains, temperature field, velocity field, macrosegregation and microsegregation. In addition, the model is found to be capable of making predictions of morphological evolution of primary grains at the onset of isothermal coarsening. The results obtained from the present simulations are validated by performing quantitative image analysis of micrographs of the rapidly oil-quenched semisolid slurry samples, collected from strategic locations along the slope and from the isothermal slurry holding bath.

Thermal segregation drives patterns of alder and willow expansion in a montane ecosystem subject to climate warming

Summary Tall‐shrub expansion into low‐statured communities, a hallmark of recent vegetative change across tundra ecosystems, involves three major genera: Alnus, Betula and Salix. Which genus expands most into tundra landscapes will determine ecosystem properties. We show that Alnus and Salix shrubs segregate thermal space (elevation × insolation) and colonize tundra landscapes differently in response to climate warming, thereby replacing different tundra types. Vegetative change estimated from repeat photography should account for hill‐slope. Methodologically, slope determines surface area estimated from orthophotos as projected pixel area times secant of pixel slope. Ecologically, the change in thermally responsive vegetative area is sensitive to terrain steepness, scaling as the cosecant of hill‐slope, so that studies should expect more shrub expansion in areas of shallow slopes than steep slopes. Repeat aerial photography in Alaska's Chugach Mountains from 1972 to 2012 orthorectified on a high‐resolution lidar digital elevation model indicated tall Salix was rare in 1972 and colonized warmer slopes by 2012. Tall Alnus colonized steeper, cooler slopes both by 2012 and by 1972. Salix and forest colonized similar thermal space. Colonization probability for both shrub genera was maximized at intermediate elevations. Alnus colonization adjacent to dwarf‐shrub tundra was twenty times as likely as Salix colonization. Salix colonization adjacent to low‐shrub/herbaceous tundra was three times as likely as Alnus colonization. Replacement of dwarf‐shrub tundra by Alnus and of low‐shrub/herbaceous communities by Salix will affect herbivores and soil properties. Good agreement between observations of plant functional type and multinomial predictions in a thermal space defined by elevation and insolation suggested that these two variables were sufficient for forecast modelling. Spatially explicit, climate‐driven generalized linear multinomial and random forest classification models in available thermal space forecast surface areas of forest, Alnus, Salix and tundra over a range of warming, modelled as upward shifted isotherms, including expected IPCC scenarios. Both modelling approaches indicated that shrubs may respond nonlinearly to warming. Synthesis. The provision of taxon‐specific coefficients for climate‐driven, spatially explicit models using high‐resolution digital elevation models is necessary for accurately forecasting vegetative change due to climate warming in montane and arctic regions.