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High-speed camera (HSC) is an advanced technology, which can be applied to observe the solid–liquid interface directly during solidification. It has never been reported that the temperature evolutions of solidification that was monitored by using cameras and their images. In this study, a new application of HSC technology was developed for the temperature evolution investigation. With this technology, the effects of the measured position, the thermocouple size and thermocouple sensitivity (delay) can be demonstrated in temperature measurement. It is important that the higher accuracy of temperature profiles can be obtained by the HSC technology. This method can be expected to analyze the temperature profiles of small melt-pool and subsequent rapid solidification process in additive manufacturing. In the end, we discussed the relationship of the recalescence rate and the solidification interface.

Slightly hypoeutectic ductile irons (4.10–4.2%CE) have a specific response to inoculation, which slightly decreased the temperature of the start of austenite formation (TAL), quickened up the start of eutectic freezing (nucleation) and increased the lowest and the highest (recalescence) eutectic temperatures. Temperature of the end of solidification increasing, with more negative level of the minimum value of the first derivative of cooling curve on the end of solidification, illustrates the efficiency of the applied inoculation to control the latter part of solidification. Increased graphitization factor, illustrating the graphite formation in the second part of eutectic reaction, sustains also the positive effect of inoculation. Inoculated irons show lower cooling rate for all of specific intervals than un-inoculated irons, with increasing tendency from beginning to the end of solidification, as specific values and also as difference between un- and inoculated irons. Inoculation potential, as ratio between the level of one specific parameter in inoculated and un-inoculated irons, has specific position, for each thermal analysis parameter, increasing from the beginning to the end of solidification. This treatment is useful not only to improve some metallurgical events at the beginning of solidification (carbide to graphite transition, graphite morphology control, eutectic cells count) but also it must be capitalized to control the last part of solidification, when the integrity of castings is decided.

The new generation of acid-lined medium-frequency coreless induction furnaces revolutionized the iron foundries, resulting higher overheating and lower S and Al content iron melt, characterized by higher eutectic undercooling solidification and consequently high chill [carbides] and unfavourable undercooled graphite morphologies sensitiveness. Having established that Al, Zr, Ti, Ca, Ba and La appear to have a key role in graphite nucleation in grey cast iron, thermal [cooling curves] investigations are undertaken to explore their effects on solidification parameters. The experimental heats are obtained in acid-lined coreless induction melting. Some important active elements are added to FeSi-based alloy, usually used as conventional inoculant in cast iron foundry industry, resulting complex inoculating systems [Al, Ca–La; Al, Ca–La, Zr; Al, Ca–La, Ba; Al, Ca–La, Zr, Ba; Al, Ca–La, Zr, Ti and Al, Ca–La, Zr, Ba, Ti]. In-mould [ceramic cup, cooling modulus of approximately 0.75 cm] inoculation is applied directly in the Quik-cup™ cooling curve analysis equipment, for the same alloy addition rate. The La effects are evaluated in low S and Al, high overheated electric grey iron solidification pattern with and without any other oxide-sulphides forming elements contribution. Study is focused on the representative temperatures during eutectic reaction and at the end of solidification, and it results in an undercooling referring to equilibrium eutectic temperature in the stable and metastable solidification system. As primary evaluation for general application, La, Ca, Al–FeSi alloy have a high efficiency in low S and Al and higher carbon equivalent grey cast irons, electrically melting, without any other active elements contribution. For specific applications, more complex La-bearing alloys are recommended, such as for higher dendritic austenite amount promotion [LaBaZrTi–FeSi alloy] or for lower eutectic recalescence [LaBaZr–FeSi alloy].

Simultaneous thermal and contraction/expansion analysis of hypoeutectic grey (lamellar graphite) and ductile (nodular graphite) cast irons solidification is recorded, using an equipment with a special designed ceramic cup, incorporating a thermocouple and contraction/expansion measuring device. Both cooling and contraction/expansion curves and their specific parameter values are displayed in a real time. The two compared cast irons occupy different and opposite positions during solidification process evolution: lower level of temperatures at the beginning and especially at the end of solidification, but higher level during the eutectic reaction for ductile cast irons. In the tested conditions, solidification of hypoeutectic cast irons with lamellar graphite is characterized by a greater undercooling during the eutectic reaction (lower ΔT1 and ΔT2, referring to the metastable eutectic temperature), with higher value for eutectic recalescence (ΔTr) and the maximum recalescence rate. Iron castings, including nodular graphite (ductile irons), show an end of solidification at higher undercooling (ΔT3), with less negative pick level of the first derivative of cooling curve. More graphitic initial expansion [edi(gr)], which favours the shrinkage formation, characterized nodular graphite iron castings. There is a good relationship between some parameters on the cooling curves and corresponding events on the contraction/expansion curves, such as solidification undercooling degrees, comparing to metastable eutectic temperature, and graphitic expansion [edi(gr)] for both tested cast irons: higher the level of ΔTr, and of ΔT1, ΔT2, ΔT3 (less negative) and GRF1 (graphitic factor), higher the [edi(gr)] level is.

The effect of Zr as a grain refiner on the solidification behavior, micro- and macrostructure of a new Al–Zn–Mg–Cu aluminum super-high strength alloy containing high Zn content was studied. The addition of 2 mass% Zr reduced the grain size from 1500 to 190 μm. Moreover, the dendritic structure of the alloy altered from a coarse, elongated and non-uniform morphology to a rosette-like shape and more uniform one. The parameters of liquidus region of cooling curve obtained from thermal analysis were in a good correlation with grain size results. The maximum of first derivative in the liquidus region was introduced beside recalescence undercooling which could predict the grain refinement level even after disappearing of recalescence in the cooling curve. Furthermore, the addition of 1 mass% Zr enhanced fraction of solid in dendrite coherency point from 21 to 31% and lessened the amounts of porosity from 2.3 to 1.4%.

The effect of cooling rate on the microstructure and solidification parameters of Mg–3Al–3Nd alloy was investigated by thermal analysis. The different cooling rates were chosen in the present work, which were attained by a stepped sand mold, ranging from 0.3 to 3.5 °C s−1. The solidification parameters were determined from the cooling curve as well as its first and second derivative curves. The results show that the microstructure and solidification parameters of Mg–3Al–3Nd alloy are influenced by changing the cooling rate. The nucleation temperature, undercooling temperature, the range of solidification temperature all increase with increasing the cooling rate. The precipitated temperature of Al2Nd and Al11Nd3 phases, recalescence undercooling temperature and total solidification time all decrease with increasing the cooling rate. The grain size of Mg–3Al–3Nd alloy is refined, and the intermetallic phases are distributed more uniformly with increasing the cooling rate. Furthermore, the volume fraction of intermetallic phases and the number density of Al2Nd particle also increase with increasing the cooling rate.

The solidification behavior of AZ Magnesium alloys in various cooling conditions was investigated using a computer-aided cooling curve thermal analysis method. In each case, the cooling curve and its first and second derivative curves have been plotted using accurate thermal analysis equipment and solidification characteristics were recognized from these curves. The cooling rates used in the present study range from 0.22 to 8.13 °C s−1. The results of thermal analysis show that the solidification parameters of AZ alloys such as nucleation temperature (T N,α), nucleation undercooling (∆T N,α), recalescence undercooling (∆T R,α), range of solidification temperature (∆T S) and total solidification time (t f) are influenced by variation of cooling rate. Also, the effect of Al content on these parameters was studied. Microstructural evaluation was carried out to determine the correlation between the cooling rate and secondary dendrite arm spacing.

Computer-aided cooling curve analysis is a reliable method to characterize the solidification behavior of an alloy. In this study, the effect of Al–5Ti–1B grain refiner on the solidification path, microstructure and macrostructure of a new Al–Zn–Mg–Cu super high-strength aluminum alloy containing high amounts of zinc was investigated using thermal analysis technique. The grain size measurement showed that Al–5Ti–1B reduces the grain size from 1402 to 405 μm. Solidification parameters in the liquidus region were in a good accordance with microstructural results. The addition of 1 mass% of Al–5Ti–1B grain refiner decreased ΔT N from 9.1 to 7.7 °C. It also diminished recalescence undercooling from 1.42 to 0.32 °C. The grain refinement also altered dendritic structure of the alloy from a coarse, elongated and non-uniform to a rosette and more uniform shape. Moreover, the grain refiner resulted in a more uniform distribution of eutectic structure between dendrite arms. Furthermore, the grain refinement enhanced fraction of solid at dendrite coherency point from 21 % for unrefined alloy to 25 % for the alloy containing 1 mass% Al–5Ti–1B. In the same trend, the addition of 1 mass% Al–5Ti–1B reduced the amounts of porosity from 2.3 to 1.8 %.

Light alloys like aluminum and its alloys have excellent physical and mechanical properties for a number of applications. The use of aluminum alloys can significantly decrease the mass of automobiles without decreasing structural strength. Therefore, the reason of this work was to determine the optimal cooling rate values, to achieve good mechanical properties for protection of this aluminum cast alloy from losing their work stability, and to make it more resistant to action in hard working conditions. The carried out investigations have allow to found that changes in the cooling rate do not cause changes in the phase composition, revealing the Al2Cu and Al5FeSi phase especially, but only changes the morphology of α + β eutectic as well as the particle size and secondary dendrite arm spacing. As a result, the number of fine crystals in per unit volume increases, leading to a fine grain structure, which influences the recalescence temperature. The purpose of this research work is to investigate the thermo-derivative interdependencies occurred in analyzed aluminum cast alloys using Universal Metallurgical Simulator and Analyzer. For the investigation, the cast AlSi9Cu aluminum alloy was used. As a result of this research, the cooling rate influence on the structure and mechanical properties changes was investigated. The cooling rate was set in a variable range of 0.16–1.25 °C s−1, where the cooling rate of 0.16 °C s−1 corresponds to freely cooling, without any forced air flow.

The influence of grain refinement—with the addition of 6 mass% Al–5Ti–B and 10 mass% Al–3Ti–B master alloys—on the temperature-based parameters of a commercial ADC12 die-casting alloy, modified with 0.04 mass% Sr, was investigated using computer-aided cooling curve thermal analysis. Results show that the addition of grain refiners caused the reaction area of the aluminium dendrite to shift up. With the addition of refiner reagents, the nucleation temperature and growth temperature for the evolution of the primary Al dendrite increased, while the recalescence temperature decreased. The dendrite coherency temperature (TDCP), time (tDCP), temperature (TN–TDCP), and time (tN–tDCP) interval for dendrite coherency and solid fraction at coherency point increased with the addition of Al–3Ti–B and Al–5Ti–B grain refiners. Nevertheless, the growth temperature of the eutectic aluminium–silicon phase remained at the modified range (563.5–565 °C) even after the addition of grain refiners. A grain-refined and modified structure was obtained after the addition of refiners, but no obvious mutual effect was found in terms of the coarsening of grain size or silicon demodification in the range of concentrations used in this study.

A model has been proposed for describing the solidification of undercooled metallic melts, on the basis that the solidification is considered as the sum of a liquid/solid cooling process without latent heat release and a latent heat releasing process without cooling. Application of the model to undercooled solidification of nickel, cobalt, zirconium, and Al–11.3Si–2Cu–0.4Fe alloy samples shows good fits to the temperature curves, and the fitting results of solid fraction curves are consistent with that from the available methods.

The aim of this work was to investigate the effect of different cooling rates on the microstructure and solidification parameters of 2024 aluminum alloy. Solidification characteristics are recognized from the cooling curve and its first and second derivative curves which have been plotted using thermal analysis technique. In this study, a mold having high cooling rate was designed and used to simulate the direct-chill casting process. The results of thermal analysis show that the characteristic parameters of Al2024 alloy are influenced by cooling rate. The cooling rates used in the present study range from 0.4 to 17.5 °C s−1. Increasing the cooling rate affects the undercooling parameters both in liquidus and eutectic solidification regions. Investigations showed that solidification parameters such as nucleation temperature, recalescence undercooling temperature, and range of solidification temperature are influenced by variation of cooling rates. Microstructural evaluation was carried out to present the correlation between the cooling rate and dendrite arm spacing.

In this research, effect of integrated Al–10Sr–1Ti–2B master alloy has been studied on the microstructure and solidification characteristics of 380.3 aluminum alloy. Thermal Analysis has been used as a technique to study the cooling curves and first derivative curves during solidification of the alloy. Effect of integrated grain refiner and modifier on solidification parameters such as α-Al dendrite growth temperature (T G,α), α-Al dendrite recalescence undercooling (∆T R,α), aluminum–silicon eutectic growth temperature (T G,E), and eutectic recalescence undercooling (∆T R,E) has been determined. By increasing master alloy content, T G,α and ∆T R,E have been increased, but, ∆T R,E has been decreased, and T G,E increases first and then decreases. Aluminum–silicon eutectic depression temperature ( $$ \Updelta T_{\text{G,E}}^{{{\text{Al}} - {\text{Si}}}} $$ ) can be used as a parameter to control the modification of eutectic silicon. The results of this research indicate that the optimum level of Al–10Sr–1Ti–2B master alloy for the simultaneous grain refinement and modification of 380.3 alloy is about 0.5 mass%.

Bismuth, antimony and strontium concentrations were optimised to alter the eutectic Al–Si phase in a commercial Al–Si–Cu–Mg alloy by way of computer-aided cooling curve thermal analysis. The results show that the eutectic growth temperature shifted to lower temperatures for all three inoculants. However, addition of Sr resulted in more depression of growth temperature compared with Bi and Sb. No further significant changes were observed with increasing the concentrations to more than 1, 0.5 and 0.04 wt% of Bi, Sb and Sr, respectively. The recalescence of these concentrations, meanwhile, showed a significant increase of magnitude. A good correlation was found between the results of thermal and microstructural analysis. For Bi and Sb, the eutectic depression temperature can be used as an individual criterion to gauge optimal levels of content in the refinement of Si, whereas for Sr, both depression temperature and recalescence magnitude must be considered. Based on the observed depression in eutectic growth temperature and recalescence, it can be concluded that the optimal concentrations to refine the eutectic Al–Si phase with Bi and Sb and to modify it with Sr at the given solidification conditions were 1, 0.5 and 0.04 wt%, respectively.

In this research, the effects of Al–5Ti–1B grain refiner and Al–10Sr modifier were studied on solidification characteristics and microstructural features of 319 aluminum alloy. Important solidification events such as recalescence and nucleation undercooling temperature and aluminum–silicon eutectic depression temperature have been evaluated using cooling curve and its first derivative curve obtained from thermal analysis of a sample. The aim of this article is to show the ability of the thermal analysis technique to predict some key parameters controlling solidification and casting process. It has been found that the thermal analysis is the identified method for a rapid on-line monitoring of metallurgical characteristics of aluminum alloy melts without conventional metallographic examination.

This article is dedicated to develop an experimental approach for directly visualizing the global freezing phase change behavior of micro liquid droplets. The infrared (IR) thermograph was proposed to image the basic solidification phenomena of droplet and to acquire its temperature variations during the transient process. In particular, the volumetric recalescence event, regarded as initiation of freezing, was revealed by IR images for the first time. Preliminary results demonstrated that the involved temperature transition due to release of the latent heat can be accurately characterized by evident color break in IR images. Further, experiments were also performed simultaneously on three kinds of droplets made of pure water, dimethylsulfoxide (DMSO) and nano liquid to grasp more precise temporal and spatial temperature distribution. Types of the occurring solidification and the initial frozen volume produced from the recalescence were generally discussed. The IR monitoring method suggests a straightforward way for detecting the freezing phase change activity and its temperature evolution at micro scale.