Cooling Curve Thermal Analysis Research Articles

Effect of Zr grain refinement on solidification behavior of Mg–3Nd alloy by cooling curve thermal analysis

Effect of Zr grain refinement on solidification behavior of Mg–3Nd alloy by cooling curve thermal analysis

Microstructure and mechanical properties of as-cast and wrought Mg–Ni in-situ formed alloys

The effects of nickel addition to magnesium in the hypoeutectic range were investigated in the as-cast and extruded conditions. At low Ni content of 5 wt-%, the grain-boundary eutectics were present in the grain refined α-Mg matrix; while at high Ni content of 15 wt-%, the eutectic constituent became the matrix of the alloy with the appearance of α-Mg rosettes. The addition of Ni up to 15 wt-% led to a significant enhancement of the strength-ductility balance. Moreover, the formation of long Mg2Ni particles at the boundaries of eutectic colonies was explained based on the cooling curve thermal analysis results. Furthermore, remarkable grain refinement by dynamic recrystallisation (DRX) and fragmentation/dispersion of intermetallic particles during hot extrusion led to the improvement of tensile strength, ductility, and toughness.

Microstructure evolution and improvement of thermal conductivity in Mg–2Sn alloy induced by La addition

Rare earth elements are commonly used to improve the properties of magnesium alloys. In this paper, the effects of various La contents on the microstructure and thermal properties of Mg–2Sn alloys were investigated. Cooling curve thermal analysis technique was adopted to reveal the microstructure evolution of Mg-2Sn-xLa alloys. La addition contributed a new eutectic reaction to occur at 639 °C and the eutectic structure was determined to be LaMgSn phase. Mg12La, Mg2Sn and matrix precipitated phases may be generated in the microstructure with further increase of La content. The thermal conductivity of Mg–2Sn alloy can be effectively improved by La addition and the maximum value 149 W/(m·K) was achieved at the Sn/La atomic ratio of 1. The thermal conductivity of Mg-2Sn-2.3La alloy could further increase to 152 W/(m·K) after solution heat treatment. The addition of La reduced the amount of solute atoms and eliminated the Sn enriched region, resulted in a rapid increase in the thermal conductivity of the Mg–2Sn alloy. The spheroidization of Mg12La phase contributed to the further improvement of the thermal conductivity after solution treatment.

Effect of microalloying by Ca on the microstructure and mechanical properties of as-cast and wrought Mg–Mg2Si composites

The effects of calcium addition at microalloying levels and hot extrusion process on the modification of the microstructure and enhancement of the mechanical properties of the Mg–3Si metal matrix composite (MMC) were studied. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), cooling curve thermal analysis, simulation based on the finite element method (FEM), thermodynamics predictions, tensile testing, and optical microscopy were used for characterization. The Ca addition modified the primary and eutectic Mg2Si phase, resulted in grain refinement of the matrix, led to better tensile properties in the as-cast condition, and gradually changed the isothermal eutectic reaction to a non-isothermal route. Moreover, hot extrusion led to the extreme grain refinement induced by dynamic recrystallization (DRX) and the break up of the eutectic structure into fine and well-distributed particles. For the Ca-containing composites, the modified primary Mg2Si particles enhanced the particle stimulated nucleation (PSN) mechanism, leading to the formation of a higher volume fraction of DRX grains with more random orientations (crystallographic texture). Accordingly, remarkable improvements in tensile properties (such as tensile toughness) were observed via extrusion of the modified in situ composites.

Role B4C Addition on Microstructure, Mechanical, and Wear Characteristics of Al-20%Mg2Si Hybrid Metal Matrix Composite

In the current study, the effect of different B4C additions (0, 2.5, 5, and 10 wt%) on the microstructural, solidification behavior, mechanical, and tribological properties of Al-20%Mg2Si composite were studied by means of scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Vickers hardness, tensile, and dry sliding wear tests. The cooling curve thermal analysis (CCTA) approach was utilized to monitor the influence of B4C particles on the solidification behavior of Al-20%Mg2Si composite. The results revealed that the addition of B4C particles up to 10 wt% reduced the nucleation temperature (TN) and growth temperature (TG) of the primary Mg2Si phase. Moreover, the proper amount of B4C added to Al-20%Mg2Si composite has a significant effect on the microstructural alteration, mechanical, and tribological properties of the composite. The mean size of primary Mg2Si in Al-Mg2Si composite was 47 μm, in which with the addition of 5 wt% B4C, the particle size decreased to 33 μm. The highest UTS (217 MPa) and El% (7%) was achieved in Al-20%Mg2Si-5%B4C hybrid composite. The cast Al-20%Mg2Si composite revealed the brittle mode of fracture with some cleavage characterization, in which with the addition of 5%B4C, the fracture mode altered to a more ductile fracture. The wear results revealed that the Al-20%Mg2Si-5%B4C hybrid composite has the highest wear resistance with the lowest wear rate (0.46 mm3/Km) and friction coefficient (µ = 0.52) under 20 N applied load compared to other fabricated composites with mild abrasion as the governed wear mechanism.

Assessment of the Microstructure, Solidification Characteristics and Mechanical Properties of AZ61 + xSr Magnesium Alloys

The effect of Sr addition on the solidification parameters of AZ61 alloy, such as liquidus and solidus temperatures, the nucleation under cooling temperature and dendrite coherency point (DCP), was investigated via the cooling curve thermal analysis method. The results revealed that by increasing the Sr content from 0 to 0.75 pct, the nucleation temperature increased about 8.2 °C and nucleation under cooling decreased about 3.5 °C. Also, it was found that increasing the Sr content suspended the dendrite coherency point and increased the solid fraction at this point. Mechanical properties of AZ61 alloy were characterized at room temperature through a compressive test. The results indicated the positive influence of Sr on compressive strength of the alloy. When the Sr content increased from 0 to 0.75 pct, the ultimate compressive stress increased from 186 to 280 MPa. This could be the result of a grain refining effect of Sr on AZ61 alloy and the formation of Al4Sr and Al3Mg13Sr intermetallic compounds.

Outcome of mix Ce and Er addition on solidification microstructure of the LM25 ( Al-7Si-alloy)

Abstract This paper highlights the effects of the additions of two rare earth elements (Ce and Er) on microstructure and to investigate the characteristic temperatures during solidification to five modified alloy. Al-7Si alloys with xEr + xCe additions (x = 0.15, 0.25, 0.4, 0.5 and 0.75) were produced by casting technique via the solidification parameters examined using computer-aided cooling curve thermal analysis (CA-CCTA). The thermal analysis tests were carried out for each one by using a thermal analysis system that includes (K-type Thermocouple, EPAD2-TH8-K, EPAD-Baes and Laptop with Dewesoft-7.5-Lt). To estimate the change in microstructure and solidification as a result of adding (Ce + Er) additions the obtained result showed that the growth TGAl-Phase and nucleation TNAl-Phase temperatures decreased to lower temperatures 614.7 °C and 615.5 °C respectively as the amount Ce, Er increased. A high amount of Ce, Er (1.5%) addition reduces the size of the platelet Si-intermetallic to very fine form.

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.

Effect of combined Ce and Er Addition on Solidification, Microstructure of the Al-7Si-alloy

This paper highlights the effects of the additions of two rare earth elements (REEs) (Ce and Er) on microstructure and to investigate the characteristic temperatures during solidification of the modified alloy. Five changes of Al-7Si alloys with xEr+xCe additions (x=0.15, 0.25,0.4, 0.5 and 0.75) were produced by casting technique via the solidification parameters examined using computer-aided cooling curve thermal analysis (CA-CCTA). The thermal analysis tests were carried out for each one by using a thermal analysis system that includes (K-type Thermocouple, EPAD-TH8-K, EPAD-Baes2 and Laptop with Dewesoft-7.5-Lt). To estimate the change in microstructure and solidification as a result of adding (Ce+Er) additions, the obtained result showed that the growth TG Al-Phaseand nucleation TNAl-Phasetemperatures decreased to lower temperatures 614.7°C and 615.5°C respectively as the amount Ce, Er increased.

Cooling curve thermal analysis of Al–Mg2Si–Cu–xSr composite

In situ composites are today being considered for industrial use, owing to the fewer production steps involved, lower production cost, and better wetting of reinforcements. This study emphasises the characteristic features of an Al–Mg2Si–Cu in situ composite, with the addition of different amounts of Sr (0.01–0.1 mass%) as a modifier reagent, by employing computer-aided cooling curve thermal analysis. The identification of microstructures and phases was carried out using a scanning electron microscope equipped with an energy dispersive spectrometer. The results show that the nucleation temperature of the primary Mg2Si, eutectic Mg2Si, and Al5FeSi phases initially increased with the addition of 0.01 mass% Sr, and subsequently decreased with further addition of the element. Two new Sr-containing phases were detected after the precipitation of primary Mg2Si phase and prior to the formation of eutectic Mg2Si phase. A relationship between the cooling rate (CR) and solidification rate (SR) was established. Based on cell coherency point, it was found that the eutectic Al–Mg2Si cell required a longer time to grow with the increment of Sr. The solid fraction of Al5FeSi and Al5Cu2Mg8Si6 + Al2Cu phases remained constant at 8 ± 1% and 3 ± 1%, respectively. The increase in the terminal freezing range and the cracking susceptibility coefficient, by 182% and 16%, respectively, shows that Sr increases the probability of hot tearing.

Morphological Evolution of Mg-Al-La-Ca Alloy Induced by a Mechanical Stirring Process

This paper aims to evaluate the morphological evolution of a magnesium-aluminum alloy (Mg-6Al-3La-1Ca) processed by a mechanical stirring process (MSP) with different stirring times. An apparatus for semisolid metal alloy processing was used to melt and obtain rheocast material. Transformation temperatures were determined at a slow cooling rate using computer-aided cooling curve thermal analysis (CA-CCTA) and differential scanning calorimetry (DSC). Isothermal mechanical stirring (605 °C), at 950 rpm, was carried out with a solid fraction of 0.29 and stirring times of 0, 1, 2, 4, 8 and 10 min, followed by fast cooling in water. The results showed that the microstructure after conventional casting (0 min—no stirring) is composed of an α-Mg dendritic matrix, Al11La3, (Al,Mg)2Ca and Mg2Ca compounds. With the 1-min stirring time, it was not possible to obtain globular structures. For stirring times longer than 2 min, a primary α-Mg globular morphology was obtained. Microstructures with 2 min of stirring time showed better globularization than those obtained under the other conditions. Morphological changes were observed for Al11La3 and (Al,Mg)2Ca after the MSP followed by fast cooling.

Effects of Er addition on the crystallization characteristic and microstructure of Al-2wt%Fe cast alloy

Effects of Er addition on the crystallization characteristic and microstructure of Al-2wt%Fe cast alloy have been investigated using cooling curve thermal analysis, optical microscopy, X-ray diffraction, SEM and TEM. Results showed that the Er addition has important effect on the crystallization characteristic of studied alloys. Thermal analysis indicated that at studied cooling rate of 1.3 °C/s, the Al-2wt%Fe cast alloy consists L→Al+Al3Fe eutectic transformation, while the alloy composes of L→Al+Al3Fe and L→Al+Al3Er eutectic transformation simultaneously with Er addition. The nucleation temperature of Al+Al3Fe eutectic increased first and then decreased with the increase of Er addition, the crystallization time of (Al+Al3Fe) eutectic decreased with the increase of Er addition. When Er addition is 0.3 wt%, the nucleation temperature has reached a peak of 650.95 °C. The addition of Er has a role of refinement on eutectic phase of Al-2wt%Fe alloy. As a favorable heterogeneous nucleation nucleus of eutectic α-Al, the primary Al3Er particle reduces the required undercooling and increases the nucleation rate. The average length of Al3Fe of 0.3 wt% Er reaches a minimum value of 37.69 μm, which is reduced by nearly half compared with that of Er free alloy. When Er content is 0.5 wt%, a small number of hollow square or diamond shaped Al3Er particles grown up to about 2 μm which can not be used as site of heterogeneous nucleation. With the content of Er from 0.1 wt% to 0.5 wt%, the growth temperature of (Al+Al3Er) eutectic increased from 626.46 °C to 635.41 °C. The supersaturated Er segregated at the α-Al/Al3Fe phase interface after solidification, and the orthorhombic Al10Fe2Er was found adhered to Al3Fe.

Effect of Cooling Rate on Solidification Behavior and Microstructure Evolution of As-Cast Mg–5Al–2Ca–2Sm Alloy

In the present work, the Mg–5Al–2Ca–2Sm alloy was fabricated in stepped type sand mold, the cooling rate varied from 0.3 to 3.5 °C/s. The solidification behavior and microstructure evolution of Mg–5Al–2Ca–2Sm alloy were carried out by computer-aided cooling curve thermal analysis method, optical microscope (OM), X-ray diffraction analysis, scanning electric microscope and transmission electron microscope. The experimental results showed that the nucleation temperature of α-Mg phase decreased with increasing cooling rate. In addition, the grain size of α-Mg phase in Mg–5Al–2Ca–2Sm alloy were 95.47 ± 1.2 μm, 88.65 ± 1.5 μm, 71.24 ± 1.7 μm and 42.35 ± 1.3 μm, which were responds to the cooling rates of 0.3 °C/s, 0.5 °C/s, 1.2 °C/s and 3.5 °C/s, respectively. There were both Al2Sm (particle structures) and (Mg, Al)2Ca (lamella structure) phases in the Mg–5Al–2Ca–2Sm alloy under different cooling rates. However, there were Mg2Ca (blocky structure) in the samples cooled in 0.5 °C/s and 0.3 °C/s. The solidification sequence of precipitated phase in Mg–5Al–2Ca–2Sm alloy could be obtained as: Al2Sm → α-Mg → (Mg, Al)2Ca → Mg2Ca. Furthermore, the volume fraction of precipitated phase increased with the cooling rate. The volume fraction of precipitated phase in Mg–5Al–2Ca–2Sm alloy were 11.86 ± 0.7%, 13.05 ± 1.2%, 16.19 ± 0.8% and 20.77 ± 0.9%, which were responds to the cooling rates of 0.3 °C/s, 0.5 °C/s, 1.2 °C/s and 3.5 °C/s, respectively.

Investigation on the effect of Sn on solidification and microstructure of AZ91 magnesium alloy using cooling curve thermal analysis

Thermal analysis technique has been used to study the effect of Sn addition on solidification characteristics and microstructure of AZ91 magnesium alloy. Solidification parameters have been extracted from cooling curves, first and second derivative curves. Different ranges of Sn between 0.1 to 1.0 wt%. have been added to the alloy. The results illustrated that the alloy containing 0.5 wt.% Sn displayed the best solidification behavior such as high nucleation temperature (TN.α), low recalescence undercooling (ΔTR), low dendrite coherency temperature and more solid fraction at dendrite coherency point. Microstructure of the alloys has been studied through optical microscopy (OM) and scanning electron microscopy (SEM). The phases were characterized by use of X-ray diffraction (XRD). Microstructural analysis showed that by adding Sn up to 0.5 wt.% into AZ91 alloy, refinement of α-Mg primary dendrites and β-Mg17Al12 took place due to the formation of new Mg2Sn intermetallic compound.

Cooling curve thermal analysis and microstructure characterization of Mg-5Zn-1Y-xCa (0–1 wt%) alloys

The effect of 0–1 wt% Ca addition on solidification pathway of Mg-5Zn-1Y alloy and its solidification characteristics such as nucleation transformation and intermetallics formation temperatures was investigated via plotting cooling and the corresponding first derivative curves. The results revealed the presence of three peaks in the first derivative curve of the ternary Mg-5Zn-1Y alloy, referring to the formation of α-Mg primary phase and intermetallics Mg3Zn3Y2 (W-phase) and Mg3YZn6 (I-phase). One more peak, corresponding to the formation of intermetallic Ca2Mg6Zn3 phase, appeared in that of the quaternary Mg-5Zn-1Y-xCa alloy when Ca content exceeds 0.1 wt%. The cooling curves showed that increasing Ca content from 0 to 1 wt% results in reducing the liquidus temperature from 659 °C to 636 °C and the average grain size from 2864 μm to 1719 μm in the Mg-5Zn-1Y alloy. The increase in Ca content also decreased the formation temperature of Ca2Mg6Zn3 phase significantly, about 29 °C, while it increased the solidus temperature from 219 °C to 233 °C. The microstructure constitution of the alloys and the formation of intermetallic phases were further confirmed through metallographic techniques including scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction analysis.

Effect of cooling rate and Al content on solidification behavior and microstructure evolution of as-cast Mg–Al–Ca–Sm alloys

In the present study, the Mg–xAl–2Ca–2Sm (x = 3, 5, 9 and 15) alloys were fabricated in sand mold with stepped type, and the cooling rates varied from 0.3 to 3.5 °C s−1. The solidification behavior and microstructure evolution of Mg–xAl–2Ca–2Sm alloys were carried out by computer-aided cooling curve thermal analysis method, optical microscope, scanning electron microscope, X-ray diffraction analysis and transmission electron microscope, respectively. The experimental results showed that the nucleation temperature and grain size of α-Mg phase decreased with increasing the cooling rate and Al content. However, the volume fraction of precipitated phase increases with cooling rate and Al content. In the Mg–3Al–2Ca–2Sm alloy cooled at 3.5 °C s−1, there were Al2Sm (rod and particle structures), Al11Sm3 (acicular structure) and (Mg, Al)2Ca (lamella structure) phases. But the Al11Sm3 phase and (Mg, Al)2Ca phase will gradually transform to the Al2Sm phase and Al2Ca phase, respectively. In addition, there were both Al2Sm (particle structures), Al2Ca (fish-bone structure) and β-Mg17Al12 (reticular structure) phases in Mg–15Al–2Ca–2Sm alloy cooled ranging from 3.5 to 0.3 °C s−1. In the Mg–xAl–2Ca–2Sm alloys, the Al2Sm phase mainly distribute in the grains, but all the Al11Sm3, (Mg, Al)2Ca, Al2Ca and β-Mg17Al12 phases distributed in the boundary of grains. The solidification sequence of precipitated phase in Mg–xAl–2Ca–2Sm alloys can be obtained: Al2Sm → α-Mg → Al2Ca → β-Mg17Al12.

Solidification, Microstructure and Mechanical Properties of Mg-2.8Nd-1.5Gd-0.5Zn-0.5Zr Cast Alloy with Erbium Addition

The thermal parameters of Mg-2.8Nd-1.5Gd-0.5Zn-0.5Zr cast alloy with 0.25 wt.% of erbium (Er) were evaluated by the computer-aided cooling curve thermal analysis(CA CCTA), whereas the microstructure analysis was investigated by the optical microscope and scanning electron microscopy. Results from the cooling curve and microstructure analysis showed that Er altered the grain size of the alloys. In addition, the grain size was reduced by approximately 19.6% with the addition of Er. Scanning electron microscopy results showed that Er formed an Mg-Zn-Nd-Er phase which distributed along the grain boundaries. Furthermore, the mechanical properties were investigated by hardness and tensile tests with Er addition. The addition of 0.25 wt.% of Er significantly improved the ultimate tensile strength and yield strength. In addition, the hardness value of Mg-2.8Nd-1.5Gd-0.5Zn-0.5Zr increased by 13.9% with Er addition.

Effect of gadolinium addition on microstructural evolution and solidification characteristics of Al-15%Mg2Si in-situ composite

The current study investigated the effects of gadolinium (Gd) addition (0, 0.3, 0.5, 1.0, and 2.0wt%) on microstructural development and solidification characteristics of hypereutectic Al-15%Mg2Si in-situ composite. Microstructural examinations were carried out via optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD). The results showed that an addition of 1.0wt% Gd, changed the morphology of primary Mg2Si from coarse dendritic to fine truncated octahedral shape. Furthermore, the average size of primary Mg2Si particles decreased from 40μm to 20μm and density increased from 495 to 1167particles/mm2. Besides that, cooling curve thermal analysis (CCTA) technique revealed that Gd addition increased nucleation and growth temperatures of primary Mg2Si phase. It is proposed that modification and refinement mechanism of Gd addition are mainly attributed to formation of tiny Al3Gd particles as the heterogeneous nucleation substrates for primary Mg2Si, which results in a refined distribution of these particles and poisoning effect by adsorbing Gd atoms, preferentially on {100} facets of Mg2Si crystals. Moreover, it is believed that formation of Gd intermetallic compounds is responsible for refinement of primary Mg2Si particles.

Effect of rare earth addition on solidification characteristics and microstructure of ZRE1 magnesium cast alloy

The thermal parameters of ZRE1 cast alloy with 1.0 wt.% of praseodymium (Pr) and 1.0 wt.% of erbium (Er) were evaluated by the computer-aided cooling curve thermal analysis (CA-CCTA), whereas the microstructure analysis was investigated by the optical microscope and field emission scanning electron microscopy. The results of the cooling curve and microstructure analyses showed that Pr and Er reduced the grain size. The thermal analysis result recorded a faster freezing time and lower solidification temperature with Pr and Er additions and 15.5 and 11.2% decrease in the grain size, respectively. Scanning electron microscopy results showed that Er formed a granular particles of Er-containing phases existed in the α-Mg matrix, while Pr formed Mg–Zn–Pr–Ce phase with secondary phase which distributed along the grain boundaries.

Effect of praseodymium and erbium additions on solidification characteristics, microstructure and mechanical properties of as–cast ZRE1 magnesium alloy

AbstractIn this research, computer‐aided cooling curve thermal analysis, microstructure analysis, hardness measurements, and tensile test were performed to investigate the effect of praseodymium (Pr) and erbium (Er) additions on as‐cast ZRE1 magnesium (Mg) alloys. Results from the cooling curve and microstructure analysis showed that praseodymium and erbium altered the grain size of the alloys. Thermal analysis result demonstrated an increased solidification rate with praseodymium and erbium additions. Furthermore, the grain size was reduced by approximately 16 % and 15 % with the addition of praseodymium and erbium, respectively. Scanning electron microscopy/energy dispersive X‐ray spectroscopy results showed that praseodymium combined with the original second phase and formed Mg−Zn‐Pr−Ce, and erbium dissolved into the α‐Mg matrix. Both additives improved the hardness and ultimate tensile strength of the ZRE1 magnesium alloy.