Cooling Rate Research Articles

Effect of Cooling Rate on the Microstructure and Mechanical Property of Nickel-Based Superalloy MAR-M247.

Heat treatment is an important process for optimizing the microstructures of superalloys, and the cooling rate after solid solution treatment is one of the most critical parameters. In this work, we treated solid solution MAR-M247 alloys with water quenching, air cooling, and furnace cooling. Microstructure characterization, hardness, and room temperature tensile tests were conducted to investigate the effect of cooling rate on the microstructure and mechanical properties of MAR-M247 alloys. The results showed that the cooling rate after solid solution treatment mainly affected the precipitation behavior of the secondary γ' phase, but it had few effects on other microstructure characterizations, including grain size, γ/γ' eutectic, and MC carbide. The water-quenched sample had the highest cooling rate (400 °C/s) and hardness (400 HV) but suffered from premature fracture because of quenching cracks. A further decrease in cooling rate from 1.5 °C/s to 0.1 °C/s deteriorated hardness (384 HV to 364 HV) and yield strength (960 MPa to 771 MPa) but increased elongation (8.5% to 13.5%). Moreover, the deformation mechanism was transformed from dislocation shearing to Orowan bypassing. The decreased yield strength was mainly due to the weakened precipitation strengthening resulting from γ'-phase coarsening. The improved elongation was attributed to not only the higher work-hardening index caused by interface dislocation networks but also the more uniform deformation, which delayed necking.

Effect of Cooling Rate on Microstructure of In Situ TiC-Reinforced Composite Surface Layers Synthesized on Ductile Cast Iron by Laser Alloying.

The microstructure of the in situ TiC-reinforced composite surface layers developed during laser surface alloying of a ductile cast iron substrate with titanium was related to the solidification conditions in the molten pool. The solidification conditions were estimated using infrared thermography. It was found that the cooling rates of the melt up to about 700 °C/s enable the complete reaction between carbon and the entire amount of titanium introduced into the molten pool. In turn, the cooling rate of about 280 °C/s for the melt containing 8.0 wt% Ti allows the TiC particles to grow in the dendritic form with well-developed secondary arms and a total size of up to 30 µm. For a constant Ti content, the cooling rate of the melt had no effect on the TiC fraction. The increase in the cooling rate elevated the retained austenite fraction in the matrix material, lowering its hardness.

Prediction of the Secondary Arms Spacing Based on Dendrite Tip Kinetics and Cooling Rate.

Secondary dendrite arm spacing (SDAS) is one of the most important factors affecting macrosegregation and mechanical properties in solidification processes. Predicting SDAS is one of the major parameters in foundry technology. In order to predict the evolution of microstructures during the solidification process, we proposed a simple model which predicted the secondary dendrite arm spacing based solely on the tip velocity (related to the tip supersaturation) and cooling rate. The model consisted of a growing cylinder inside a liquid cylindrical envelope. Two important hypotheses were made: (1) Initially the cylinder radius was assumed to equal the dendrite tip radius and (2) the cylindrical envelope had a fixed radius in the order of the dendrite tip diffusion length. The numerical model was tested against experiments using various Pb-Sn alloys for a fixed temperature gradient. The results were found to be in excellent agreement with experimental measurements in terms of SDAS and dendrite tip velocity prediction. This simple model is naturally destined to be implemented as a sub-grid model in volume-averaging models to predict the local microstructure, which in turn directly controls the mushy zone permeability and macrosegregation phenomena.

Structure of Argon Solid Phases Formed from the Liquid State at Different Isobaric Cooling Rates

By the method of molecular dynamics, computer simulation of the processes of isobaric cooling of argon particle systems under initial conditions with a temperature of 150 K at pressure values from 0.1 to 4 MPa to a temperature of 40 K with cooling rates of 108, 109, 1010, 1011 and 1012 K/s was performed. As a result of a computer experiment, coordinate arrays of particles were obtained, which were subjected to the procedure of three-dimensional Voronoi partitioning to identify and calculate the number of elementary cells of the crystal structure. Analysis of the structure of argon solid phases formed during isobaric cooling allowed us to deduce an estimated pattern between the concentration of FCC (face-centered cubic) cells in solid argon and the cooling rate from the liquid state. The evaluation of the orientation of the axes of translation of crystal cells in the array of particle coordinates made it possible to classify the solid phases formed as a result of cooling as single crystals, glassy media with the inclusion of clusters and single cells of FCC structures. It was revealed that during isobaric cooling at a rate not exceeding 108 K/s, argon completely crystallizes, at isobaric cooling rates of 109–1010 K/s, the union of elementary cells of the crystal structure into clusters is observed in glassy argon, and at rates of 1011 K/s and higher at pressures of 1 MPa and lower, solid vitreous phases of argon are formed in which no crystal structure cells are detected.

Effect of Cooling Rate on Powder Characteristics and Microstructural Evolution of Gas Atomized β-Solidifying γ-TiAl Alloy Powder

Effect of Cooling Rate on Powder Characteristics and Microstructural Evolution of Gas Atomized β-Solidifying γ-TiAl Alloy Powder

Effect of Cooling Rate on Structural, Corrosion, and Mechanical Properties of Cobalt–Chromium–Molybdenum Dental Alloys

Effect of Cooling Rate on Structural, Corrosion, and Mechanical Properties of Cobalt–Chromium–Molybdenum Dental Alloys

Effect of the Cooling Rate on the Microstructure of Directionally Solidified Casting (CMSX-4 Ni Superalloy)

Effect of the Cooling Rate on the Microstructure of Directionally Solidified Casting (CMSX-4 Ni Superalloy)

Effect of Cooling Rate on Microstructure, Shape Memory Effect and Mechanical Properties of Cu–13Al–5Fe High-Temperature Shape Memory Alloy Fabricated by Laser Powder Bed Fusion

Effect of Cooling Rate on Microstructure, Shape Memory Effect and Mechanical Properties of Cu–13Al–5Fe High-Temperature Shape Memory Alloy Fabricated by Laser Powder Bed Fusion

Effects of Different Heating and Cooling Rates during Solution Treatment on Microstructure and Properties of AA7050 Alloy Wires.

In the present study, the effects of varying heating and cooling rates during the solution treatment process on the microstructure and properties of AA7050 alloy wires were investigated using tensile tests, metallographic microscopy, electron backscattered diffraction, and transmission electron microscopy. It was found that the recrystallized grain size of the alloy, subjected to method of rapid heating, exhibited a smaller and more uniform distribution in comparison to method of slow heating. The low density of η' strengthening phases after the artificial aging treatment was formed using air cooling method. Meanwhile, by using the water quenching method sufficient solute atoms and more nucleation sites were provided resulting in a large number of η' strengthening phases being formed. In addition, the alloy processed using the water quenching method displayed higher strength than that treated using the air cooling method for the T6 and T73 states. Furthermore, coarse precipitates formed and less clusters were observed in the matrix, while high density nanoscale clusters and no continuous precipitation are formed when using the water quenching method.

Influence of Cooling Rate and Alloying by “Cr, V, and Ni” on Microstructure and High-Temperature Wear Behavior of SiMo Ductile Iron

AbstractSiMo ductile irons, typical heat-resistant materials, are subjected to varied wear environments during operation in high-temperature applications. SiMo ductile iron castings of different thicknesses were cast in investment and greensand molds, achieving a wide range of cooling rates. The present work aims to investigate the effect of the cooling rate and alloying elements (Cr, V, and Ni) on the microstructure and the abrasive wear behavior of these grades of SiMo ductile iron at high-temperature 700 °C under different loads. Thermodynamic calculations were used to propose the phase diagrams, critical transformation temperatures, and phase volume fractions in all SiMo alloys by using the Thermo-Calc software then verified by and Differential Scanning Calorimetry (DSC). The microstructure of unalloyed SiMo ductile cast iron consists of graphite nodules and carbides embedded in the precipitates at the grain boundary regions in a ferrite matrix. The alloyed SiMo microstructure contains nodular graphite and the carbides promoted by the alloying elements (Cr and V). The alloyed SiMo alloys exhibit higher wear resistance than unalloyed ones. These wear results support that the microstructure plays a chief role in wear loss. The combination of M6C, VC, and M7C3 carbides embedded in a ferrite-pearlite matrix (alloyed SiMo) seems to be more resistant to wear than the ferritic matrix with lamellar pearlite and eutectic M6C carbides (unalloyed SiMo).

Physical simulation of the heat-affected zone in nickel-free high-nitrogen stainless steel weld at various peak temperatures and cooling rates

Nickel-free high-nitrogen stainless steel (NFHNSS) stands out for its remarkable strength, ductility and toughness making it a preferred choice for applications demanding robust structural integrity. Physical simulations of NFHNSS heat-affected zone under different peak temperatures and cooling rates were studied. Based on the phase diagram simulated from Thermo Calc, physical simulations were carried out on 16 specimens with varying peak temperatures ( 800 °C, 900 °C, 1000 °C and 1250 °C) and various cooling rates (CR) as (25 °C/s, 15 °C/s, 5 °C/s and 2 °C/s). The specimens were grouped and characterised based on peak temperature under varying cooling rates. The microstructural changes, precipitates, hardness and tensile properties of the base metal and heat-affected zone (HAZ), were investigated. HAZ subzones are very sensitive to peak temperature and cooling rate lead to variation in grain size. The test results showed significant refinement in HAZ grain size and significant improvement in strength with a fast cooling rate. Furthermore, transmission electron microscopy analysis showed Cr2N formation with respect to the cooling rate. Yield and tensile strength increased with an increase in CR and ductility reduced slightly. Whereas, with an increase in peak temperature yield strength, tensile strength reduced and ductility increased due to grain coarsening

Investigation of Relationship Between Cooling Rate, Microstructure, Porosity and Corrosion in As-Cast Samples of the 1050 Aluminum Alloy Subjected to Different Levels of Gamma Radiation

Investigation of Relationship Between Cooling Rate, Microstructure, Porosity and Corrosion in As-Cast Samples of the 1050 Aluminum Alloy Subjected to Different Levels of Gamma Radiation

On the Effect of the Melt Cooling Rate upon Spinning on the Structure of the Surface Layers of Fe77Ni1Si9B13 Alloy Ribbons

On the Effect of the Melt Cooling Rate upon Spinning on the Structure of the Surface Layers of Fe77Ni1Si9B13 Alloy Ribbons

Effect of Cooling Rate on Microstructure, Phases, and Properties of Al-Si Coated Hot-Press-Forming Steel Sheets

Effect of Cooling Rate on Microstructure, Phases, and Properties of Al-Si Coated Hot-Press-Forming Steel Sheets

The Role of the Weld Metal Structure Formation in Selecting Rational Cooling Rates When Welding K80 Strength Grade Steel

The Role of the Weld Metal Structure Formation in Selecting Rational Cooling Rates When Welding K80 Strength Grade Steel

Regulation Law of Tempering Cooling Rate on Toughness of Medium-Carbon Medium-Alloy Steel.

Temper embrittlement is a major challenge encountered during the heat treatment of high-performance steels for large forgings. This study investigates the microstructural evolution and mechanical properties of Cr-Ni-Mo-V thick-walled steel, designed for large forgings with a tensile strength of 1500 MPa, under different tempering cooling rates. Optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to analyze the microstructural features. The results demonstrate that the embrittlement occurring during air cooling after tempering is attributed to the concentration of impurities near Fe3C at the grain boundaries. The low-temperature impact toughness at -40 °C after water quenching reaches 29 J due to the accelerated cooling rate during tempering, which slows down the diffusion of impurity elements towards the grain boundaries, resulting in a reduced concentration and dislocation density and an increased stability of the grain boundaries, thereby enhancing toughness. The bainite content decreases and the interface between martensite and bainite undergoes changes after water quenching during tempering. These alterations influence the crack propagation direction within the two-phase microstructure, further modifying the toughness. These findings contribute to the understanding of temper embrittlement and provide valuable guidance for optimizing heat treatment processes to enhance the performance of high-performance steels in large forgings.

Investigation of Melt Pool Geometry, Cooling Rate, and Microstructure Formation in Laser Surfacing of Al 7075 Alloy: Numerical Simulation and Experimental Analysis

Investigation of Melt Pool Geometry, Cooling Rate, and Microstructure Formation in Laser Surfacing of Al 7075 Alloy: Numerical Simulation and Experimental Analysis

The Influence of the Cooling Rate of the Melt during Spinning on the Structure of the Contact and Free Sides of the Fe77Ni1Si9B13 Alloy Tapes

The Influence of the Cooling Rate of the Melt during Spinning on the Structure of the Contact and Free Sides of the Fe77Ni1Si9B13 Alloy Tapes

Modeling Competitive Reaction Heat Sources and Variable Cooling Rates Applicable to Thermal Runaway Onset in Lithium-Ion Batteries

Two main types of exothermic processes are known to initiate thermal runaway in Lithium-Ion batteries. If mechanical failure of the separator causes an electrical short circuit, the cell’s energy can be released through electrochemical discharge reactions. The full stored energy can be released as heat within the cell for internal short circuits, raising the cell temperature by several hundred degrees Celsius. Different thermochemical reactions occur when Lithium-Ion cells are heated; the anode and cathode materials decomposing with the electrolyte can result in similarly large temperature rises. Our work shows that thermodynamics constrain key reactant species for both decomposition paths to be in common. Interactions and competition between these chemical pathways for heat release are considered in this modeling study, including relative magnitudes of thermal contributions from each reaction pathway and limiting reactant effects. An effective oven temperature concept is defined, which allows thermal runaway initiation via internal short circuits versus external heating to be compared. Temperature and reaction inhomogeneities occurring in the presence of internal localized internal short circuits lead to variations in the balance between electrochemical and thermochemical reactions across the domain of the cell. A simple homogeneous analysis is compared to a higher-dimensional inhomogeneous analysis. The effectiveness external cooling strategies to mitigate an internal short circuit event is investigated. Acknowledgements: This article has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in and to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan https://www.energy.gov/downloads/doe-public-access-plan. This abstract has been approved for release as SAND2023-01585A.

Influence of the Cooling Rate on Austenite Ordering and Martensite Transformation in a Non-Stoichiometric Alloy Based on Ni-Mn-In

The effect of the melt cooling rate on the atomic ordering of austenite and, as a consequence, on the martensitic transformation of a nonstoichiometric alloy of the Ni-Mn-In system has been studied. In situ TEM observations revealed differences in the mechanism of phase transformations of the alloy subjected to different cooling conditions. It is shown that during quenching a high density of antiphase boundaries (APB) is formed and the alloy is in the austenite–martensitic (10M and 14M) state up to a temperature of 120 K. In a slowly cooled alloy, a lower APB density is observed, and a two-stage transformation, L21/B2 → 10M → 14M, occurs in the range of 150–120 K.