Computer-aided Cooling Curve Analysis Research Articles

Homogenization heat treatment influence on microstructure evolution and mechanical properties of as-cast Al–Li–Cu–Mg–Zr alloy for lightweight aerospace application

Al–Li–Cu–Mg–Zr alloys are widely used in the aerospace industry for different applications and make an excellent concurrent to high-performance composites. This family of alloys has remarkable properties like low density, high elastic modulus, high strength and specific stiffness, fracture toughness, fatigue crack growth resistance, and improved corrosion resistance.The present work aims to investigate a family of Al–Li alloys by employing suitable characterization techniques such as computer-aided cooling curve analysis and thermal dilatometry to characterize the as-cast alloy. The characterization temperatures of the alloy were obtained and the phase transformation temperatures were concluded as thermal expansion inflection points as well. Furthermore, the homogenization heat treatment effect of the alloy is examined through optical microscopy (OM), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Vickers microhardness testing to determine the optimum heat treatment time. The results reveal the formation of δ′, δ and β’ precipitates in the alloy after different hours of homogenization heat treatment. Notably, our investigation identifies the optimum heat treatment time for the alloy as 26h at 515 °C, resulting in reduced hardness and barely any chemical segregation. These findings contribute to the characterization of as-cast Al–Li alloys and the understanding of microstructure evolution and mechanical properties during homogenization heat treatment that offer a valuable insight for enhancing their performance in aerospace applications.

Enhancing microstructure and mechanical properties of nickel aluminium bronze alloy through tin addition

This article describes the changes in the microstructure, cooling curve characteristics and mechanical properties of cast Nickel Aluminium Bronze alloy (NAB) alloy that were produced by the addition of various amounts of Tin (Sn). The solidification parameters were recorded using a computer-aided cooling curve analysis setup, and optical and scanning electron microscopes were utilised to study the evolution of the microstructure. The chemical composition of different phases generated in the NAB alloy with and without Tin was investigated using an X-ray diffraction technique. With the addition of tin, the alloy's microstructure changed from columnar to equiaxed grain structures, and the ideal microstructure was produced at a Tin concentration of roughly 1.0 weight percent. The formation of the high temperature α and the grain boundary Sn rich phases across the alloy microstructure as a result of further addition has a considerable impact on the alloy's increased hardness (upto 69%) and tensile strength (upto 28.4%) compared to untreated NAB alloy. Influence of Sn on microstructure transformation is confirmed by the decline in alloy nucleation temperatures, the reduction in undercooling intensity, and the decrease in cooling rate during solidification. The addition of Tin to the NAB alloy caused morphological changes in the kappa (K) phases, which are also reported in the this article. In addition to this, the research makes an attempt to describe the mechanism underlying the formation of equiaxed grains and phase transformations in Sn-treated NAB alloys.

Calorimetric analysis of Mg–Li ultra light magnesium alloy

The Thermal-Derivative Analysis, or Computer-Aided Cooling Curve Analysis, is a commonly used method for determining the solidification parameters of metals and alloys. Knowledge of the enthalpy, kinetics and broad characteristics of the transformations taking place during the cooling of an alloy can be obtained with the proper configuration of analytical equipment and arrangement of test techniques. This work practically analyses the changes occurring in the Mg–4.5Li–1.5Al alloy as a result of the modification of the structure by the addition of TiB and Sr. The results indicate that adding grain refinements significantly affects the microstructure and thermal parameters of Mg–4.5Li–1.5Al alloy. The nucleation temperature and solidus temperature decrease with the addition of chemical reagents. Compressive strength improved due to the refinement of grain size. The results confirmed that thermal-derivative analysis is suitable for analysing changes in cast magnesium alloys.

Determining the solidification characteristics of Manganese bronze (MAB) alloy using computer-aided cooling curve analysis

Computer-aided cooling curve analysis (CACCA), known for its reliability and simplicity was used to study the material properties of manganese bronze (MAB) alloy. MAB alloy, due to its high strength and corrosion resistance, is a staple material for marine applications. Since the alloy is difficult to machine, non-heat treatable, and complex to fabricate, casting is the only cost-effective process of producing products of the material. As the literature is scant on the MAB’s high-temperature properties, this study is aimed at determining the thermo-physical properties of the alloy required for casting simulation by carrying out Newtonian and Fourier analysis of the recorded temperature of the solidifying alloy from liquidus state.

Review of thermal characterization techniques for salt-based phase change materials

Phase change materials (PCM)-based energy storage system is a quite promising technology for the efficient usage of the excess solar energy produced and utilize it at the hour of high demand. The major challenge here is the selection of PCMs for energy storage applications. Inorganic PCMs possess higher thermal conductivity and energy storage capacity when compared to organic PCMs. Thus, inorganic PCMs have a great potential to be used in energy storage systems majorly in medium to high-temperature applications where organic PCMs cannot be used. An accurate and reliable data on the thermophysical properties of the PCMs is essential before its selection and installation of a energy storage system. In this study, various characterization methods based on calorimetry, temperature difference, cooling rate, and cooling curve used to date are described. Methods such as conventionally used differential scanning calorimetry (DSC), T-history method, and computer-aided cooling curve analysis (CACCA) are reviewed and discussed in this study. The two modes of CACCA, Newtonian, and Fourier techniques are explained. The advantages and limitations associated with all these methods are outlined. Inverse heat conduction problem (IHCP)-energy balance method based on CACCA which is devoid of the limitations associated with the conventional characterization methods is discussed. Thermal conductivity is the main characterization parameter of the PCMs and therefore methods to measure thermal conductivity are critically reviewed in this study. Thermal cycling stability is discussed in the context of the review.

Solid Fraction Effect on Solidification of Semisolid Forging A380 Alloy

ABSTRACT In recent years, it has been shown that high pressurized solidification has been impeding cooling rate measurement in semisolid forging of aluminum alloys. This has restricted the establishment of solidification behavior, especially at the semisolid interface. In this paper, the solid fraction effect on semisolid forging of A380 aluminum alloy was investigated. Computer-aided cooling curve analysis, microscopic evaluation, and Archimedes density measurement were used to analyze the results. It was found that during solidification, the application of pressure at 0.2% solid fraction not only increased the cooling rate but also reduced the solidus temperature. The application of pressure at the same solid fraction also reduces the SDAS to 15.54 µm. However, pressure application at 63% solid fraction recorded the lowest porosity volume percentage and highest density values of 0.133% and 2.723 g, respectively. Further increase in the cooling rate had a slight effect on the SDAS refinement.

Understanding Solidification Behavior of Salt Phase Change Material with Added Carbon Nanoparticles Using Computer-Aided Cooling Curve Analysis

Understanding Solidification Behavior of Salt Phase Change Material with Added Carbon Nanoparticles Using Computer-Aided Cooling Curve Analysis

Functional and Environmental Advantage of Cleaning Ti5B1 Master Alloy

One of the greatest environmental goals for the aluminum alloys industry is generating higher quality products by introducing cleaner input materials while maintaining low production costs. A typical dilemma for the master alloy producers is the cleanness level of the master alloy since insoluble inclusions could serve as inoculants during the solidification process. In this work, commercial Ti5B1 master alloy is used for grain refinement of Al7Si4Cu aluminum alloy and compared with the cleaned master alloy that contained a lower amount of residual refractory oxides and salts. Metallography analysis was used for grain size measurement while Computer Aided Cooling Curve Analysis was used for assessment of the undercooling and heat release values. In all instances, specimens treated with the cleaned master alloy showed smaller grains in the final structure and lower undercooling values. The difference in released heat between liquidus and recalescence temperatures was about 25% in specimens where added 0.66 wt% of cleaned master alloys compared to specimens where the commercial master alloys were added. Using cleaner Ti5B1 master alloy with a higher number of TiAl3 and TiB2 particles improves its grain refinement efficiency and transmits fewer impurities in produced parts. Producing cleaner master alloy would be beneficial from economic and environmental aspects by increasing its value and service time of produced parts besides simplifying the recycling process at the end of parts life-cycle.

Computer aided cooling curve analysis (CACCA) of ADC-12 alloy

Computer aided cooling curve analysis (CACCA) is used for the determination of different characteristics of metals/alloy during solidification process. The recorded temperature data and the alloy characteristics such as solid fraction and latent heat of fusion derived using CACCA, provides an in-depth understanding of the alloy’s solidification process and these information can be used as an input to casting simulation processes. Newtonian analysis a mathematical technique commonly used to determine the fraction of solid during solidification and also to fit DBL to the first derivative curve. However, few researchers have further extended this technique to determine diffusivity and enthalpy of the alloys. In this context, the presented paper explores the procedures (both experimental and theoretical) of Newtonian analysis to determine the specific heat of the alloy and also to report the solidification characteristics of ADC 12 alloy. The CACCA indicates that the nucleation of ADC 12 alloy solidifying at a rate of 0.4 °C/s will start at 574 °C with an undercooling of 46 °C and grow at 577 °C with a recalescence of 3 °C. On the other hand, the specific heat of ADC12 alloy obtained using Newtonian analysis varied between 1025 and 1275 J/Kg-K for temperature range of 600–400 °C respectively.

Effect of La on microstructure and corrosion behavior of 10%TiB2(p)/Al–5%Cu composites

The effect of La on microstructure and corrosion behavior of 10%TiB2(p)/Al–5%Cu composites was studied by using computer-aided cooling curve analysis (CA-CCA), X-ray diffraction, EDS, SEM, TEM and electrochemical testing. The experimental results showed that the La addition reduced the solidification rate of composites, decreased the nucleation temperature of primary α-Al, enhanced the transformation temperature of Al–Cu eutectic and narrowed the liquid–solid interval. Meanwhile, Al2.12La0.88 phase formation was found after adding La to the composites, and the precipitation of CuAl2 phase decreased with the increase of La content. The segregation of large agglomerates containing TiB2 clusters and second phases was improved obviously after the addition of La, which resulted in more uniform microstructure of composites. Moreover, proper La enhanced the corrosion resistance of 10%TiB2(p)/Al–5%Cu composite in 3.5% sodium chloride solution.

Cooling curve thermal analysis, phase constitution, and solidification characteristics of cast Mg–5Gd–2Y–xNd–Zr alloys

Mg–RE alloys are high-strength magnesium alloys with great application potential. The solidification pathways and microstructure formation of most Mg–RE alloys are still under discussion. In the present research, phase constitution and solidification characteristics of Mg–5Gd–2Y–xNd–Zr (x = 0, 2, 4, 6) alloys were investigated using a Computer-Aided Cooling Curve Analysis (CA-CCA) system, together with microstructure observation and phase identification methods including SEM, EDS, and XRD. The results show that the solidification microstructure of Mg–5Gd–2Y–Zr alloy was composed of α-Mg and Mg24RE5 phase. And the addition of Nd leads to the formation of β phase through a eutectic reaction, L → Mg24RE5 + α-Mg + β. Combining the CA-CCA and microstructure observation results, the non-equilibrium solidification route and solid fraction–time relationship of Mg–5Gd–2Y–xNd–Zr (x = 0, 2, 4, 6) alloys was summarized. Besides, hot tearing susceptibility of the investigated alloys was evaluated according to their solid fraction–time relationship using Clyne–Davies’ criterion.

An experimental approach based on inverse heat conduction analysis for thermal characterization of phase change materials

A new method based on solution to inverse heat conduction problem for the assessment of solidification parameters of PCM salts has been proposed. The method estimates the mold -salt interfacial heat flux and it is used to calculate the latent heat of salt PCMs using calorimetry based energy balance equations. This method is more accurate compared to Computer Aided Cooling Curve Analysis (CACCA) techniques as it eliminates the drawbacks involved with base line fitting calculations and errors introduced due to the improper selection of solidification points. Pure salt PCMs such as KNO3 and solar salt were used for the validation of this technique. Both air and furnace cooling were adopted to demonstrate the effect of cooling rate on solidification characteristics. The wettability of salt samples on mild steel surface was analyzed to account for the difference in the thermal behavior of salts.

Determination of the latent heat of fusion and solid fraction evolution of metals and alloys by an improved cooling curve analysis method

In this work, a new computer-aided cooling curve analysis method (CA-CCA) called metal/mold energy balance method (MEB) is presented. Its originality relies on taking into account the thermal history, the mass, and the heat capacity of both the sample and the mold containing it, for the determination of the latent heat of fusion and the evolution of the solid fraction of metallic samples contained into metallic molds without using a baseline curve. The MEB method is based on the numerical processing of the cooling curves of the sample and the mold, which are obtained using two thermocouples, one located at the thermal center of the sample and the other placed into the mold wall. The mold containing the sample is thermally isolated at its top and bottom. The method was applied to explore its capability to determine values of latent heat of fusion and solid fraction evolution when compared to reported values in the literature of five metals of commercial purity (Cd, Zn, Sn, Pb, and Al) and two Al-based alloys (Al–7%Si and Al–14%Cu). The performance of the MEB method was compared with the results obtained by processing the cooling curves of the metal and alloys under study using the Newton baseline method, the dynamic baseline method, and the equation-based Newtonian method. The obtained results suggest that MEB method offers a simple and easy way to obtain accurate experimental values of latent heat of fusion with small errors respect to the reference reported values, while results on solidification paths are similar to those predicted by the other CA-CCA methods.

Effect of Biodiesel Mixture Derived from Waste Frying-Corn, Frying-Canola-Corn and Canola-Corn Cooking Oils with Various ‎Ages on Physicochemical Properties

Waste frying, corn and canola cooking oil biodiesels were produced through the transesterification ‎process and their properties were measured. Three different mixtures of biodiesel with the same blending ratio, namely, WCME1 (frying-corn biodiesel), WCME2 (frying-canola-corn biodiesel) and WCME3 (canola-corn biodiesel), were prepared. The effect ‎of ‎blending ‎biodiesel with various ages ‎‎(zero months (WCME3), eight months (WCME1), and 30 months (WCME2)) on kinematic ‎viscosity and‎ density was investigated under varying temperature and volume fraction. It was found that the kinematic viscosity of WCME2 remained within the ranges listed in ASTM D445 (‎1.9–6.0‎ mm2/s) and EN-14214‎ (‎3.5–5.0‎ mm2/s) at 30 months. It was also observed that both viscosity and density decreased as the temperature increased for each fuel sample. In order to improve the cold flow properties of the samples, the Computer-Aided ‎Cooling Curve Analysis (CACCA) technique was used to explore the crystallization/melting ‎profiles of ‎pure ‎methyl biodiesel as ‎well their blends. The results show that pure WCME2 has the lowest cold flow properties compared to other samples. Furthermore, 10 ‎correlations ‎were developed, tested and compared with generalized ‎correlations for the ‎estimation of the ‎viscosity and densities of pure biodiesels and their ‎blends. These equations depend on the temperature and volume fraction of pure components as well as the properties of the fuel.

Assessment of Solidification Parameters of Salts and Metals for Thermal Energy Storage Applications Using IHCP-Energy Balance Combined Technique

Solar energy storage technologies have proved to be promising in terms of providing uninterrupted power supply. The phase change materials (PCMs) with their higher heat storage capacity are more efficient than sensible heat storage materials. In this study, a new method for thermal analysis of PCM salts was proposed. The method was based on the estimation of heat flux at the mold–salt interface using solution to inverse heat conduction problem and characterizing the salt using a simplified energy balance method. It was advantageous over other computer-aided cooling curve analysis methods as it eliminated the use of curve fitting approach involved in baseline calculations. KNO3 and NaNO3 salts were used to validate this method. The solidification parameters like cooling rate, liquidus and solidus temperatures, solidification time and latent heat were assessed. The results of the analysis were in agreement with the data reported in the literature.

Effects of Ca/Al ratio and extrusion process on Mg–Al–Ca alloys to produce a high toughness in-situ composite

ABSTRACTThe microstructures and tensile properties of Mg–Al2Ca–Mg2Ca in situ composites (Mg–17Al–8Ca, Mg–14Al–11Ca and Mg–12.5Al–12.5Ca) with different Ca/Al ratios have been studied in both as-cast and extruded conditions. The results indicated that by increasing Ca/Al ratio, new Mg2Ca intermetallic introduces to the Al2Ca phase in eutectic structure. Computer-aided cooling curve analysis confirmed the formation of these phases during solidification. Extrusion process not only altered the size of large bulk Al2Ca intermetallic, but also changed the size and morphology of intermetallics in eutectic structure considerably. The results showed that with increasing Ca/Al ratio, tensile properties of cast composites changes slightly, but significant enhancement is observed after extrusion process. The strength and elongation values of Mg–12.5Al–12.5Ca (Ca/Al = 1) alloy improved from 166 MPa and 2% in as-cast condition to 465 MPa and 12% in hot-extruded condition. The reason for the improved toughness may be attributed to the formation of finer and well-dispersed distribution of hard (Al2Ca) and ductile (Mg2Ca) phases. It was found that hot extrusion easily deforms ductile Mg2Ca phase in comparison with Al2Ca phase. In as-extruded condition, there are more very fine dimples than as-casted condition because extrusion process leads to formation of fragmented tiny particles and more uniformity distribution of Al2Ca particles.

Assessment of solidification characteristics of carbon-inoculated Mg-3%Al melt by thermal analysis

Abstract The Mg-3%Al melt was inoculated by carbon with different holding time. The effect of holding time on grain refining efficiency was evaluated. The solidification characteristics of the carbon-inoculated Mg-3%Al melt with different holding time were assessed by computer-aided cooling curve analysis. The results showed that Mg-3%Al alloy could be effectively refined by carbon inoculation. Slight fading phenomenon occurred with increasing the holding time to 60 min. Carbon inoculation could significantly influence the shape of cooling curves of Mg-3%Al melt. The nucleation starting and minimum temperatures increased. The recalescence undercooling and duration decreased to almost zero after carbon inoculation. The grain refining efficiency of carbon inoculation could be assessed by the shape of the cooling curve and solidification characteristic parameters including nucleation starting and minimum temperatures, recalescence undercooling and duration.

Variation of solid fraction with cold flow properties of biodiesel produced from waste frying oil

Biodiesel sample utilized in the study was produced from waste frying oil by a base catalyzed one step transesterification reaction. The feedstock oil and the samples produced were tested in accordance with the standards designated by European Committee for Standardization and also by American Society for Testing and Materials. Cold Flow Properties (CFP), namely Cloud Point (CP), Cold Filter Plugging Point (CFPP) and Pour Point (PP) were determined. Since the three CFP should occur at specific solid fractions during freezing, the objective was to examine in details the whole solidification history to estimate the corresponding solid fractions at these temperatures. The so-called computer-aided cooling curve analysis employed in metal casting industry was modified and applied to the current biodiesel sample. Indications of CP, CFPP and PP were noted as slope changes on the cooling curve and also on its first derivative curve. The Newtonian thermal analysis was utilized to estimate the solid fractions in the solid-liquid mixture at CP, CFPP and PP during solidification. The fraction of the solidified biodiesel in the mixture jumped from 0.18 to 0.39 when the CFPP temperature was reached. The visual observations were in agreement with the calculations.

Cooling Curve Analysis of Micro- and Nanographite Particle-Embedded Salt-PCMs for Thermal Energy Storage Applications

In recent years, the focus of phase change materials (PCM) research was on the development of salt mixtures with particle additives to improve their thermal energy storage (TES) functionalities. The effect of addition of microsized (50 μm) and nanosized (400 nm) graphite particles on TES parameters of potassium nitrate was analyzed in this work. A novel technique of computer-aided cooling curve analysis was employed here to study the suitability of large inhomogeneous PCM samples. The addition of graphite micro- and nanoparticles reduced the solidification time of the PCM significantly enhancing the heat removal rates, in the first thermal cycle. The benefits of dispersing nanoparticles diminished in successive 10 thermal cycles, and its performance was comparable to the microparticle-embedded PCM thereafter. The decay of TES functionalities on thermal cycling is attributed to the agglomeration of nanoparticles which was observed in SEM images. The thermal diffusivity property of the PCM decreased with addition of graphite particles. With no considerable change in the cooling rates and a simultaneous decrease in thermal diffusivity, it is concluded that the addition of graphite particles increased the specific heat capacity of the PCM. It is also suggested that the additive concentration should not be greater than 0.1% by weight of the PCM sample.

Effects of Mg2Sn intermetallic on the microstructure and tensile properties of Al–15% Mg2Si–X% Sn composite

Abstract