Dta and Heat-Flux DSC Measurements of Alloy Melting and Freezing

Boettinger, William J.; Kattner, Ursula R.; Moon, Kil-Won; Perepezko, John H.

doi:10.1016/b978-008044629-5/50005-7

Cited by 168 publications

(149 citation statements)

References 18 publications

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“…The heat flux was measured on heating between 700˚C and 1450˚C under an inert atmosphere using a heating rate of 10˚C min -1 . The solidus temperatures were identified from the DSC thermograms in line with the NIST recommendations [57]. This enabled homogenisation heat treatment temperatures to be identified close to the solidus, whilst avoiding incipient melting.…”

Section: Methodsmentioning

confidence: 94%

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The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

Christofidou

Jones

Pickering

et al. 2016

Journal of Alloys and Compounds

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The effects of Ni:Co and Al:Ti ratios on the room temperature microstructure, hardness and lattice parameter of twenty-seven quinary Ni-Co-Al-Ti-Cr alloys have been evaluated. All of the alloys exhibited a uniform γ-γ′ microstructure. Differential scanning calorimetry (DSC) showed that the liquidus and solidus temperatures of the alloys, increase with greater Al:Ti ratios, decrease with Cr concentration and remained largely unchanged with respect to the Ni:Co ratio. Neutron diffraction measurements of the γ and γ′ lattice parameters revealed that the lattice misfit in all of the alloys was positive and increased with Ti concentration (i.e. lower Al:Ti ratio) regardless of the concentration of Cr, or the ratio of Ni:Co. Importantly, alloys with a Ni:Co ratio of 1:1, were found to have consistently greater lattice misfits than alloys with Ni:Co ratios of either 1:3 or 3:1. The measured lattice misfits were found to be strongly correlated with the Vickers hardness of the alloys, suggesting that lattice misfit plays a key role in the strengthening of γ-γ′ alloys of this type.

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Section: Methodsmentioning

confidence: 94%

“…Whilst the NIST guidelines were used when obtaining the liquidus and solidus temperature [57], the precipitate solvus temperatures were determined as the first deviation from the baseline on heating, as this indicated the beginning of precipitate dissolution rather than the maximum rate of dissolution [59].…”

Section: Dsc Resultsmentioning

confidence: 99%

The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

Christofidou

Jones

Pickering

et al. 2016

Journal of Alloys and Compounds

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“…23,24) During heating of samples, several endothermic thermal effects could be investigated, and liquidus temperature could be obtained as the last endothermic peak temperature. 24) The undercooling for onset crystallization could be defined as ΔT=TL-Tx, where TL represents liquidus temperature and Tx represents onset crystallization temperature for one kind crystal.…”

Section: Crystallization Behaviors Of Mould Fluxes Investigated By Dtmentioning

confidence: 99%

Effect of TiO2 Addition on Crystallization Characteristics of CaO-Al2O3-based Mould Fluxes for High Al Steel Casting

Shu

Hou

et al. 2015

ISIJ Int.

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Crystallization behaviors of new developed CaO-Al2O3 based mould fluxes with TiO2 addition for casting of high-Al steels were investigated by using DTA techniques combined with SEM-EDS and XRD analysis. XRD and SEM analyzed on the crystallized samples showed that the sequence of crystal precipitation for TiO2-free mould flux during cooling was MgO, and followed by Ca12Al14O33 during cooling. The sequence of crystal formation for TiO2-bearing mould fluxes during cooling is CaTiO3 to MgO, and then Ca12Al14O33. Continuous cooling transformation diagrams (CCT) were constructed for analysis of the crystallization behaviors. The Undercooling values for onset crystallization of various crystals were calculated by using liquidus temperature obtained by heating DTA and crystallization temperature of various crystals. The crystallization temperatures of CaO-Al2O3 based mould fluxes increased with increasing TiO2 content. The undercooling values for onset crystallization of CaTiO3 decreased with increasing TiO2 content, which indicating that the crystallization of CaTiO3 was enhanced with increasing TiO2 content. The undercooling values for onset crystallizations of Ca12Al14O33 and MgO only changed slightly with increasing TiO2. This indicated that crystallizations of Ca12Al14O33 and MgO crystals were only slightly influenced by TiO2 addition. The overall crystallization of mould fluxes was enhanced with increasing TiO2 content.

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“…The Fe-rich intermetallic precipitates have higher solution temperatures and are usually stable over 600˝C [31]. Microstructural observations revealed that the Fe-rich intermetallic particles, shown in Figure 6, precipitate at grain boundaries during partial remelting.…”

Section: Phase Evolution and Alloying Element Distribution During Parmentioning

confidence: 98%

Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

Binesh

Aghaie-Khafri

2016

Metals

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Microstructural and mechanical behaviors of semi-solid 7075 aluminum alloy were investigated during semi-solid processing. The strain induced melt activation (SIMA) process consisted of applying uniaxial compression strain at ambient temperature and subsequent semi-solid treatment at 600-620˝C for 5-35 min. Microstructures were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). During the isothermal heating, intermetallic precipitates were gradually dissolved through the phase transformations of α-Al + η (MgZn 2 ) Ñ liquid phase (L) and then α-Al + Al 2 CuMg (S) + Mg 2 Si Ñ liquid phase (L). However, Fe-rich precipitates appeared mainly as square particles at the grain boundaries at low heating temperatures. Cu and Si were enriched at the grain boundaries during the isothermal treatment while a significant depletion of Mg was also observed at the grain boundaries. The mechanical behavior of different SIMA processed samples in the semi-solid state were investigated by means of hot compression tests. The results indicated that the SIMA processed sample with near equiaxed microstructure exhibits the highest flow resistance during thixoforming which significantly decreases in the case of samples with globular microstructures. This was justified based on the governing deformation mechanisms for different thixoformed microstructures.

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Dta and Heat-Flux DSC Measurements of Alloy Melting and Freezing

Cited by 168 publications

References 18 publications

The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

Effect of TiO<sub>2</sub> Addition on Crystallization Characteristics of CaO-Al<sub>2</sub>O<sub>3</sub>-based Mould Fluxes for High Al Steel Casting

Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

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