Liquid Quenching Research Articles

Influence of Liquid Quenching on Phase Composition and Properties of Be-Si Eutectic Alloy

By the method of quenching from the liquid state (splat-quenching), it is first revealed the formation of mixture of metastable supersaturated substitutional solid solutions in the eutectic alloy Be-33at.% Si. Cast samples are obtained by pouring melt into a copper mold. High cooling rates during liquid quenching are achieved throw the well-known splat-cooling technique by spreading a drop of melt on the inner surface of a rapidly rotating, heat-conducting copper cylinder. The maximum cooling rates are estimated by the foil thickness. The melt cooling rates (up to 108К/s), used in the work, are sufficient to form amorphous phases in some eutectic alloys with similar phase diagrams, but it is found those rates are insufficient to obtain them in the Be-Si eutectic alloy. The X-ray diffraction analysis is carried out on a diffractometer in filtered Cobalt Ka radiation. Microhardness is measured on a micro-durometer at a load of 50 g. The electrical properties, namely the temperature dependences of relative electrical resistance, are studied by the traditional 4-probe method of heating in vacuum. The accuracy of determining the crystal lattice period of the alloy, taking into account extrapolation of the reflection angle by 900, is ± 3•10-4 nm. It is found that even at extremely high rate of quenching from the melt, instead of the amorphous phase formation, the occurrence of two supersaturated substitutional solid solutions, based on Beryllium and Silicon, is revealed. This fact is established by the obtained dependences of their lattice periods values on the alloying element content. So, during the formation of metastable eutectic structure, a supersaturated with Beryllium solid solution of Silicon has period a = 0.5416 nm, and a supersaturated with Silicon solid solution of low-temperature hexagonal Beryllium has periods a = 0.2298 nm, c = 0.3631 nm. The positive role of the liquid quenching method in increasing the level of mechanical characteristics (microhardness and microstresses) in rapidly cooled Be-Si films is shown. It has been demonstrated that the difference in the atomic radii of the elements significantly affects the distortion of crystal lattices of the formed supersaturated solid solutions, and a significant value of microstresses (second-order stresses) in the Silicon lattice supersaturated with Beryllium is estimated, which, of course, leads to a significant increase in the microhardness, namely: there is an increase in microhardness in the Be-Si alloy under the conditions of applied method of quenching from the liquid state by more than 1.7 times compared to cast eutectic alloy and more than 6 times higher in comparison with the eutectoid cast Iron-Carbon alloy. The obtained polytherm of electrical resistance of the alloy under conditions of continuous heating in vacuum confirms the metastable nature of obtained new phases during quenching from the liquid state.

Rapid growth kinetics of intermetallic Ni3Ti compound under electrostatic levitation state

The rapid solidification mechanism of Ni3Ti intermetallic compound within undercooled Ni75Ti25 and Ni74Ti18Al8 alloys was investigated by electrostatic levitation(ESL) and liquid quenching(LQ) techniques. The dendritic growth velocity of Ni3Ti phase in these two alloys revealed power law relations versus liquid undercooling, whose maximum value was 138.9 mm s−1 for binary Ni75Ti25 alloy at 255 K(0.15TL) undercooling, while it was only 54.7 mm s−1 at 222 K(0.13TL) undercooling for ternary Ni74Ti18Al8 alloy. The crystalline structure of Ni3Ti phase in both alloys was characterized by fine dendrites under LQ state, whereas it displayed faceted growth mode under ESL condition. In addition, the Ni3Ti grains of Ni75Ti25 alloy show a transition from incompletely to completely surrounded by the grain boundaries.

Effect of Liquid Quenching on Hydroprocessing of Heavy Crude Oils in a Fixed-Bed Reactor System

The effect of liquid quenching during the hydroprocessing of a heavy crude oil in a fixed-bed reactor system was explored. Experiments were carried out at various operating conditions in a pilot plant equipped with two fixed-bed reactors in series loaded with a triple catalyst system and necessary hardware for injecting quench fluids between reactors. The feed and quench liquid were prepared by splitting a heavy crude oil into two fractions, called light and heavy fractions. The heavy fraction was used as the feed to the reactors, whereas the light fraction was injected between reactors as the quenching liquid. To establish a reference case, a conventional hydrogen quenching scheme was also evaluated by injecting hydrogen instead of the light fraction. It was observed that hydrogen quenching produced only marginally better quality because of a more favorable H2/oil profile. Yet, it was determined that this approach (hydrogen quenching) requires the handling of large volumes of gas, which increases compressor capacity and equipment size. Liquid quenching, on the other hand, decreases the reaction severity by increasing the liquid hourly space velocity (LHSV), which affects product quality although not significantly. Compared with hydrogen quenching, liquid quenching dramatically reduces the quench volumetric rate and consequently compression costs, which makes this approach an economically attractive option for industrial application.

Metastable phases in the Ni75Nb12B13 alloy prepared under nonequilibrium conditions

The structure of Ni75Nb12B13 alloys prepared by liquid quenching (LQ) and mechanical alloying (MA) has been studied by x-ray diffraction. The alloy prepared by LQ at a cooling rate of ∼106 K/s is shown to be fully amorphous, while MA yields an amorphous-crystalline material in which the predominant phase is an fcc Ni〈Nb,B〉 solid solution. The thermal stability of the alloys and their structural transformations on heating have been studied by differential scanning calorimetry. The amorphous phase obtained by LQ is shown to crystallize at 490°C. After heating to 720°C, the alloy consists of two equilibrium phases: Ni21Nb2B6 (τ) and Ni5Nb3B2 (z). Heating the MA alloy to 720°C leads to the formation of a stable τ-phase, while the Ni-based fcc solid solution remains supersaturated and, hence, metastable. Increasing the milling time leads to the formation of nanocrystalline τ and Ni3B phases, in addition to the Ni-based fcc solid solution, which corresponds to the equilibrium phase composition of the Ni75Nb12B13 alloy in the Ni-Nb-B phase diagram. The effect of high-energy milling on the phase composition of the alloy is similar to that of heat treatment.

Distortion Behaviour and Mechanical Properties of AlCu4Mg1 Sheet Components after High-Pressure Gas Quenching in Comparison to Liquid Quenching

The quenching process after solution annealing of age hardenable aluminium alloys is necessary for an improvement of the mechanical properties, but also tends to result in distortion, especially in thin or complex shaped parts, and requires a costly reworking. High-pressure gas quenching can reduce distortion compared to liquid quenching, because of the better temperature uniformity during quenching. A determination of the distortion behaviour of different serial parts of the aluminium wrought alloy 2024cl (AlCu4Mg1,clad) points out, that high-pressure gas quenching offers predominantly excellent values regarding the dimensional accuracy after quenching compared to liquid quenchants. In comparison to the conventional heat treatment, similar values in strength, hardness and electrical conductivity have been determined after gas quenching and aging of different aluminium alloys (2024, 6013, and 7075), Furthermore, the residual stresses have been investigated and could be clearly reduced after gas quenching. Verzugsverhalten und mechanische Eigenschaften von AlCu4Mg1 Serienblechteilen nach der Hochdruck-Gasabschreckung im Vergleich zur Flussigkeitsabschreckung Der Abschreckprozess nach dem Losungsgluhen aushartbarer Aluminiumlegierungen ist fur die nachfolgende Auslagerung notwendige Voraussetzung. Bei der Abschreckung von dunnen oder komplex geformten Bauteilen konnen dabei Mas- und Formanderungen entstehen, die eine kostenintensive Nacharbeit erforderlich machen. Die Hochdruck-Gasabschreckung besitzt das Potenzial diese Verzuge aufgrund der besseren Temperaturgleichmasigkeit bei der Abschreckung zu reduzieren. Die Ermittlung des Verzugsverhaltens an Blechbauteilen aus der Serienfertigung der Aluminium-Knetlegierung 2024cl hat ergeben, dass die Hochdruck-Gasabschreckung gegenuber der Abschreckung in flussigen Medien uberwiegend bessere Ergebnisse hinsichtlich der Mashaltigkeit der Bauteile liefert. Im Vergleich zur konventionellen Flussigkeitsabschreckung konnten nach der Gasabschreckung und anschliesender Auslagerung ahnliche Festigkeiten bzw. Harten und Leitfahigkeiten fur verschiedene Aluminiumlegierungen (EN AW-2024, EN AW-6013 und EN AW-7075) ermittelt werden. Des weiteren konnten die Eigenspannungen durch eine Gasabschreckung deutlich reduziert werden.

Effects of liquid quenching and subsequent heating on the structure of Co-Al Alloys

The phase composition and structure of Co-Al alloys after liquid-quenching (LQ) and subsequent heating were determined by x-ray diffraction, differential thermal analysis, and differential scanning calorimetry. After LQ, the Co-19.5 at % Al alloy consisted of two phases: CoAl (B2 structure, a=0.2852 nm) and an fcc Co1 − xAlx solid solution (a=0.3573 nm). The phase composition of the LQ alloy and the lattice parameters of the intermetallic phase CoAl and solid solution corresponded to a solidification temperature of 1100°, rather than to the eutectic temperature (1400°C). Heating to 1000°C brought the alloy to the equilibrium state. In the range 25–28 at % Al, the LQ alloys were single-phase and consisted of Co-enriched CoAl (B2). Decomposition of this intermetallic phase during heating in the calorimeter gave rise to an exothermic peak at 680°C and led to precipitation of hcp Co, which converted to an fcc Co1 − xAlx solid solution on heating to 1000°C. The activation energy of the decomposition process, evaluated by the Kissinger method, was Ea=125 ± 10 kJ/mol. The LQ Co-71.4 at % Al alloy consisted of three phases: metastable quasicrystalline phase (similar in structure to Al14Co3Ni3), Co2Al5, and CoAl. Heating brought the alloy to the equilibrium state (Co2Al5), with an exotherm near 690°C. The activation energy of this phase transformation was Ea=195 ± 15 kJ/mol. The LQ alloys containing 76.5 and 82 at % Al were single-phase and consisted of monoclinic Co4Al13 or Co2Al9 with reduced lattice parameters.

Microstructure and Crystal Orientation of Rapidly Solidified (Bi,Sb)<SUB>2</SUB>(Te,Se)<SUB>3</SUB> Alloys by the Liquid Quenching Technique

A rapid solidification process was found to form unidirectional crystal structures in (Bi,Sb)2Te3 and (Bi,Sb)2(Te,Se)3 based thermoelectric alloys. This fine microstructure with its unidirectional crystal orientation is expected to yield high value thermoelectric properties because the fine grain size is extremely effective in decreasing thermal conductivity by boundary scattering of phonons and because this crystal orientation is extremely effective in decreasing the electrical resistivity (increasing the carrier mobility). The rapidly solidified alloys were prepared by a single-roller liquid quenching method. These alloys were shaped as a thin foil with thicknesses ranging from 5 to 20 μm. The crystal orientation was analyzed by the x-ray diffraction method and the microstructure was observed by optical microscopy and SEM of the thin foil samples. The crystal grains of the rapidly solidified foils were very fine and highly oriented. The thermoelectric properties were measured for p-type Bi0.4Sb1.6Te3 and the n-type Bi1.9Sb0.1Te2.6Se0.4 compacted alloys. The figures of merit of 3.5 × 10−3 K−1 for p-type alloy and 3.3 × 10−3 K−1 for n-type alloy were obtains. It is proposed that the rapid solidification is very useful technique for the improvement of thermoelectric properties.

Thick Glassy Water by Liquid Quenching on a Diamond Wafer

By quenching water on a liquid nitrogen cooled diamond wafer, we have produced 0.7 mm thick glassy water disks about 1000 times thicker than previously produced by quenching liquid water. Our in situ measured cooling rates of 110−271 K/s are far lower than the 105−106 K/s previously thought necessary for formation of a glass from liquid water. Conversely, these are also the highest measured cooling rates that we are aware of for quenching this thickness of water. The glassy disks quenched on diamond are transparent, have a density of 1.04 g cm-3, and exhibit a glass-transition temperature of 138 K and a crystallization temperature range of 150−190 K.

過冷液滴急冷法によるへん平状非晶質合金粉末の製造とその応用

過冷液滴急冷法によるへん平状非晶質合金粉末の製造とその応用

Giant Magnetoresistance in Cu-Co Alloys Produced by Liquid Quenching

Giant magnetoresistance (GMR) in Cu-Co alloys produced by liquid quenching has been confirmed. A supersaturated solid solution was obtained in a quenched state and fine-grained magnetic precipitates in fcc Cu-rich matrix were obtained upon annealing. It has been found that Cu80Co20 alloy annealed at 500°C for 1 h exhibits a giant magnetoresistance ratio as large as 4% at room temperature.

New Decagonal Al–Ni–Fe and Al–Ni–Co Alloys Prepared by Liquid Quenching

New Decagonal Al–Ni–Fe and Al–Ni–Co Alloys Prepared by Liquid Quenching

Kinetics of precipitation and of relaxation of precipitation-induced stresses in aluminium-silicon alloys

Liquid quenching as well as solid quenching of aluminium-silicon alloys yields an aluminiumrich matrix supersaturated with silicon. Ageing of quenched alloys implies silicon precipitation (cf. phase diagram in Ref. i). Since the atomic volume of silicon as precipitated (diamond structure) is much larger than as dissolved in the Al-rich matrix, large stresses will develop in the Al-rich phase on ageing. This is clearly demonstrated by the behaviour of the Al-rich phase lattice parameter, aAl, as a function of ageing time, t, cf. Fig. 1 (2, 3). Silicon precipitation from the Al-rich phase causes an overall increase of the Al-rich phase lattice parameter, but precipitation-induced stresses and their subsequent relaxation cause a hump, AaXl(tmax), (3). This hump occurs at much shorter times for liquid-quenched (LQ) than for solid-quenched (SQ) alloys (compare Fig. la to Fig. ib). For the LQ alloys the determination and interpretation of ~Xl(tmax) is hardly possible because of the interwoven effects On the Al-rich phase lattice parameter of silicon precipitation, precipitation-induced stresses and relaxation stresses. In this letter the silicon precipitation and subsequent relaxation of precipitation-induced stresses in solid-quenched AISi alloys are investigated by measurement of the Al-rich phase lattice parameter as a function of temperature and time of ageing.

On the Formation of Rapidly Quenched Ti-Pd and Pd-Si Alloys: A Comparison with Mechanically Alloyed Materials

AbstractWe have investigated the formation of amorphous and microcrystalline alloys of Pd-Si and Ti-Pd. In order to allow comparison of the two methods, both liquid quenching (LQ) for rapid solidification and mechanical alloying (MA) techniques were employed. Characterization of the materials was obtained through X-ray diffraction and differential thermal analysis (DTA).Both the LQ and MA syntheses yielded amorphous Pd80Si20alloys, with very similar X-ray line widths and crystallization temperaiures. However, the MA alloys contained as minority component a second phase, indexed to Pd3Si.Quite different results were obtained for the Ti-Pd alloys. LQ splats containing 42, 66, and 80 at % Ti were not amorphous but microcrystalline, as might be expected from the very similar atomic radii of Ti and Pd. In contrast, a broad range of amorphicity, from approximately 42 to 85 at % Ti, was found in the MA synthesized materials. Overall, these results show that the two methods, LQ and MA, differ in the mechanisms of amorphization. This conclusion is further supported by additional MA and LQ experiments on ternary Ti-Pd-Cu alloys.

On the Factors Controlling Glass Forming Ability of Metallic Alloys Formed by Fast Liquid Quenching

Solid solubility maps are constructed for Ni alloys and Zr alloys using the ratio of atomic radii rA/rB and the heat of mixing LHM of the liquid alloy as coordinates. Highly soluble elements appear wcll separated from insoluble elements in this map. The map is also able to discriminate between easy glass forming and non glass forming alloys. It is argued that the map contains the factors usually considered to be responsible for the glass forming ability of alloys. High solid solubility and glass forming ability exclude each other. Die Diagramme der Loslichkeit binarer Legierungen von Ni und Zr werden dargestellt. Das Ver-haltnis der Atomradien rn/rB und der Bildungswarme AHM der fliissigen Legierung werden als Koordinaten genornmen. Es wird festgestellt, daB die hochloslichen Elemente von den unloslichen deutlich separiert sind. Das Diagramm zeigt ebenfalls den Unterschied zwischen den leicht amorphisierbaren sowie nicht-amorphisierbaren Legierungen. Es wird hervorgehoben, das das Diagramm Faktoren enthllt, die fur die Bildung des arnorphen Zustands verantwortlich sind. Gute Loslichkeit und die Fahigkeit zur Bildung einer amorphen Struktur schliesen sich aus.

Superconducting Properties and Flux Pinning in Liquid Quenched Nb-Ga Alloys

ABSTRACTNb75−xGa25+xtapes (1≤ x ≤ 6) were prepared by liquid quenching technique in an argon atmosphere. The transition temperature Tc, upper critical field Hc2 and critical current density Jc were measured in both as-quenched and annealed samples. The values of Tc (onset) ranged from 16.5 to 18.0K in the asquenched samples and increased upon annealing up to 20.0 K. Similar increase was also observed in the values of Hc2 (4.2 K) from ∼190 kOe to values higher than the attainable field of 220 kOe. For annealed samples near stoichiometric composition, Hc2 was estimated to be higher than 300 kOe. The critical current densities of these tapes are relatively low [Jc (4.2 K) ≤ 2 × 104A/cm2] compared to other melt-quenched A-15 compounds. Flux pinning force, FP, does not obey a single scaling law. The existence of two peaks in FP at low temperatures and of only one peak at 13.4 K for 1 ≤ x ≤ 4 is discussed in terms of the microstructural characteristics of the samples.