Crystallization Temperature Interval Research Articles

Effects of Si addition on crystallization process and soft magnetic properties of high-Fe and high-Cu-content Fe–Si–B–P–Cu nanocrystalline alloys

In this study, the effects of Si content on the glass-forming ability (GFA), thermal stability, annealing window, nanocrystallization process, and soft magnetic properties (SMPs) of Fe86.3-xSixB10P2Cu1.7 (x = 0, 1, 2, 3, and 4, denoted as Si0, Si1, Si2, Si3, and Si4, respectively) alloys with high Fe and Cu contents were investigated. Moderate addition of Si (x = 1, 2, and 3) enhanced the GFA and suppressed the precipitation of compound phases, thus leading to a large crystallization temperature interval (ΔTx) exceeding 185 °C for the alloys. Appropriate addition of Si also resulted in the formation of high-density and fine pre-existing α-Fe nanocrystals in as-spun ribbons and a high growth active energy of α-Fe crystals during the subsequent nanocrystallization process for the Si1, Si2, and Si3 alloys, enhancing competitive growth between α-Fe crystals and resulting in fine nanostructure and excellent SMPs of the nanocrystalline alloys (NAs). As a result, the Si1, Si2, and Si3 NAs obtained by annealing at 420 °C for 30 min exhibited excellent SMPs with saturation magnetic flux density (Bs) up to 1.84 T and a low coercivity (Hc) of approximately 10 A/m. In addition, statistical analysis of the relationship between the average grain size (D) of α-Fe crystals and Hc values of the NAs indicated that an Hc α D3 dependence is observed when the D is less than approximately 30 nm, while this dependence follows the well-known Hc α D6 relationship when the D is above 30 nm. The dependency relationship between D and Hc of NAs can guide the selection of an appropriate annealing process to optimize their SMPs.

Enhanced Ms of Fe-rich Fe-B-Cu amorphous/nanocrystalline alloys achieved by annealing treatments

The effects of Fe content and annealing temperature on the microstructure, thermal stability and soft magnetic properties of Fe-rich Fe83.5+xB15-xCu1.5 (x = 0.5, 1.0, 1.5, 2) alloys were investigated. The results show that when the Fe content is going up to 85%, alloys still have the capability of forming a single amorphous phase. After that, glass-forming ability (GFA) is weakened and crystalline phase appears. In terms of thermal stability of alloys, the increase in Fe content is beneficial to obtain a larger crystallization temperature interval (ΔTx = 144.4 ℃), which is conducive to the process of heat treatment and the preparation of amorphous/nanocrystalline soft magnetic materials. The optimum annealing treatments (430 ℃×10 min) can yield the high saturation magnetization (Ms) of 208 emu/g, which is comparable to the one of alloy Fe-Si 3 wt%.

Effect of melt superheat treatment on solidification behavior and microstructure of new Ni–Co based superalloy

A new type of Ni–Co based superalloy was prepared by vacuum induction melting (VIM), and the effects of superheat on element distribution, dendrite segregation, and solidification microstructure refinement of the new Ni–Co based superalloy are revealed. The effect of solidification structure treatment under different conditions was quantitatively studied by differential scanning calorimetry (DSC), scanning electron microscope (SEM), and electron probe micro analyzer (EPMA). The results indicated that the nucleation undercooling increased and the crystallization temperature interval decreased with the rise of the melt temperature; As the superheat temperature rised, the size of the phase was refined; the secondary dendrite arm spacing of the alloy decreased continuously; and the dendritic segregation of the alloy decreased. It was found that the critical temperature of melting energy for the new Ni–Co based superalloy clusters is about 1550 °C. The maximum positive segregation element of the new Ni–Co-based superalloy is Ti, and the maximum negative segregation element is W; When the temperature increased from 1450 °C to 1600 °C, the segregation coefficient of Ti increased from 0.54 to 0.63, and the segregation coefficient of W decreased from 1.9 to 1.5. When the superheat was increased, the atomic cluster size decreases, and the effect of refining the solidification structure of the new Ni–Co-based superalloy is more significant.

Identifying the optimal amorphous precursor alloy system for dual-phase nanostructure formation according to the impurity tolerance and crystallization mechanism

The amorphous precursor alloys for nanostructure with high Bs always exhibit a low impurity tolerance, inhibiting mass production. Here, we comparatively studied the FeBSiCu, FeBPSiCu and FePSiCu alloy systems in Fe83B12-xPxSi4Cu1 (x = 0–12) alloys made with industrial raw materials. Fully amorphous ribbons were readily prepared in the Fe83B12Si4Cu1 and Fe83P12Si4Cu1 alloys. It is difficult to avoid the surface crystallization induced by the impurities in Fe83B12-xPxSi4Cu1 (x = 2–8) amorphous alloys with a relatively high amorphous formability. The Fe83B12Si4Cu1 alloy exhibits a large crystallization temperature interval (ΔT) which can be further widened by P micro-alloying. The macro-substitution of B by P will lead to a significant decrease of ΔT. The ΔT of the novel Fe83P12Si4Cu1 alloy can be effectively widened by increasing the Fe content and microalloying of B, exhibiting a good potential for the combination of superior ΔT, AFA and impurity tolerance. The low impurity tolerance in the Fe83B12-xPxSi4Cu1 alloys is ascribed to the significant difference in the metallurgical properties of the Fe–B and Fe–P alloys, needing new impurity purification processes. These results will bring a new perspective to develop high Bs precursor alloys and experimental references for critical industrialization.

Uncommon K-foiditic magmas: The case study of Tufo del Palatino (Colli Albani Volcanic District, Italy)

Leucititic rocks, K-foiditic in composition are volumetrically important in the Colli Albani (also known as Alban Hills) volcanic district (Central Italy) especially during the most explosive phases of activity (>200 km3). The Colli Albani tephra in distal (>500 km) deposits indicates that K-foiditic magma chambers fed large explosive eruptions (i.e., tens of km3 of pyroclastic rocks). Major oxides, trace elements and Raman spectra were measured on the glasses and minerals occurring in the K-foiditic scoria clasts of the ~530 kyr-old Tufo del Palatino, erupted in the Colli Albani volcanic district. The Colli Albani pre-eruptive magmatic system is characterized by the aH2O < 1 and high CO2 activity in the melt, as testified by the CO3 in the clinopyroxene melt inclusions, by the early crystallization of CO3-bearing apatite and by the high CO2 activity in the free volatile phase that led to crystallization of calcium carbonate in the scoria clast vesicles. The K-foiditic magmas plot on the Cpx + Lc + melt divariant surface of the Ol-Cpx-Lc-Mel-H2O-CO2, P ≥ 0.2 GPa and T ≤ 1100 °C. The assimilation of cold carbonate by hot magmas is an important open-system process allowing the establishment of aH20 < 1 condition in the volatile-rich, Colli Albani magma chambers where the stability fields of the olivine and phlogopite are reduced in favor of clinopyroxene and leucite. Trace element modelling indicates large amount of carbonate assimilation (~12.4 wt%) involved in the differentiation process that origins the K-foiditic magmas starting from a K-rich, phonotephritic parental magma. The large amount of assimilate carbonate is consistent with the peculiar distribution of the latent heat across the crystallization interval of the phonotephritic parental magma. The isenthalpic assimilation process is very efficient in the phonotephritic magma because the crystallization of clinopyroxene and leucite in equilibrium with a K-foiditic melt proceeds over a relatively large temperature interval (>200 °C) and the K-foiditic melt shows low viscosity (104Pa·s at 1000 °C). Actually, the low melt viscosity, that increases the growth rate, and the large temperature interval of crystallization are intrinsic factors that increase the release of the latent heat of crystallization from the phonotephritic parental magma. Extrinsic factors enhancing the assimilation process efficiency are the thickness (>4 km) and the depth (down to 5–7 km) of the carbonate substrate in the Colli Albani volcanic district.

Effect of Ti addition on microstructure and high-temperature soft magnetic properties of nanocrystalline (Fe0.9Co0.1)72.7Al0.8Si13.5B9Cu1Nb3 alloy

The crystallization behavior and microstructure of (Fe0.9Co0.1)72.7Al0.8Si13.5B9-xCu1Nb3Tix(x = 0,1,2) alloys were analyzed by the differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). The soft magnetic properties of alloys after thermal treatment were studied by the temperature dependence of initial permeability (μi-T curves). Experimental results show that the proper addition of Ti can decrease the onset temperature of primary crystallization Tx1 for precipitating soft magnetic phase from 506 °C for x = 0–487 °C for x = 1 and increase the onset temperature of second crystallization Tx2 from 669 °C for x = 0–703 °C for x = 2. The extended onset temperature of second crystallization Tx2 of 703 °C and crystallization temperature interval ΔTx of 199 °C make the 650oC-annealed (Fe0.9Co0.1)72.7Al0.8Si13.5B7Cu1Nb3Ti2 alloy exhibit superior magnetic softness at room- and high-temperatures. And the 610oC-annealed (Fe0.9Co0.1)72.7Al0.8Si13.5B8Cu1Nb3Ti1 alloy shows improved high-temperature magnetic softness at 450–650 °C with respect to Ti-free (Fe0.9Co0.1)72.7Al0.8Si13.5B9Cu1Nb3 alloy.

Effect of Trace Elements on the Crystallization Temperature Interval and Properties of 5xxx Series Aluminum Alloys

The influence of alloying elements Er, Zr, Cu, Si and Zn on the crystallization temperature interval, microstructure, mechanical properties and corrosion behavior of Al-Mg-Mn alloy were studied by differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), tensile testing, electrochemical measurements and nitric acid mass loss test (NAMLT). The results show that the crystallization temperature range of Al-Mg-Mn alloy with addition of Zn decreased 4.7 °C. Cold rolled alloys mainly contain S texture, Copper texture, Brass texture, and Goss texture; the content of the S texture is the highest. With the addition of trace elements, the second phase Al3Er, Al3Zr, Al2CuMg, Mg2Si and MgZn2 can be formed, which can improve the tensile strength and yield strength of Al-Mg-Mn alloy. The addition of the alloying element Zn can also improve the intergranular corrosion resistance of the Al-Mg-Mn alloy.

Thermometry of Nickel Bearing Chlorites from the Kolskii Massif (Northern Urals)

The chemical composition of chlorites from the rocks that are conventionally classified as the residual weathering mantle of the Kolskii ophiolite massif was studied. The chlorites exhibit high Mg/ (Mg + Fe) atomic ratio values (Mg#) of 0.78–0.96 and elevated Si content (2.95–3.74 apfu), but are relatively poor in Al (1.28–2.66 apfu). In terms of octahedral occupancy (RVI is 5.52–5.98 and [R3+]VI is 0.87–2.04 apfu), they are classified as the trioctahedral subgroup. The NiO content in the chlorites varies from 0.2 to 21 wt %; in addition, the tabular low-Ni and high-Ni chlorite grains are often tightly intergrown. There is a pronounced negative correlation between NiO and MgO content. The crystallization temperature estimated using chlorite geothermometers varies widely. The crystallization temperature interval is 125–300°C or higher with a statistical maximum in the region of 175–300°C for the low-Ni chlorites and 50–250°С with a statistical maximum in the region of 75–125°С for the high-Ni chlorites. In addition, the high-Ni chlorites demonstrate a gradual decrease in temperature as the nickel content increases. This correlation indicates the important role of temperature as an ore generation factor during the formation of the oxide–silicate nickel deposits that are associated with the Kolskii massif. These tendencies support the conclusion that the hydrothermal processes not only preceded lateritization, but also played a significant part in the level of nickel concentration in phyllosilicates.

Solidification with crystallization behavior of molten blast furnace slag particle during the cooling process

The centrifugal granulation technique has been considered for the recovery of waste heat retained in molten blast furnace slag while simultaneously obtaining high value slag particles for cement auxiliary materials. During granulation the high wind speed is expected to acquire high vitreous slag particles formed by centrifugal force of the atomizer, but result in significant energy consumption and low-grade heat of the cooling air. To address this problem, we established a two-dimensional symmetrical model to describe the crystallization behavior of blast furnace slag droplets by the enthalpy method via self-programming. The radiation heat transfer between slag particle and the wall was considered as well as non-isothermal solidification, including a narrow temperature interval of crystallization. The results display the evolutions of the local cooling rate and crystal phase content distribution. The effects of the diameter, initial temperature of the slag particle, wind initial temperature and wind speed are also discussed. Furthermore, two correlations of the average cooling rate and final crystal phase content with dimensionless parameters were developed respectively, to predict slag quality under various operational conditions.

Forecasting of temperature intervals of crystallization and homogenization in monocrystal-line nickel-base superalloy

Purpose. Obtaining predictive regression models with which one can adequately calculate the critical temperatures for monocrystalline nickel-base superalloy without conducting previous experiments.Methods of research. Experimental values were processed in the Microsoft Office program suite in the EXCEL package with the least squares method, with the obtaining of the “parameter-property” correlation dependencies with the obtaining of mathematical equations of regression models that optimally describe these dependencies and the construction of trend lines.Results. The simulation of temperature characteristics of monocrystalline nickel-base superalloy is carried out. The ratios of doping elements and regression models are indicated, with the help of which it is possible to predict the width of the temperature interval of crystallization and the optimum temperature of homogenization for an alloy.Scientific novelty. For the first time, the relations Kγ′ and Kγ are proposed, by which one can adequately predict the temperature characteristics for multicomponent compositions of monocrystalline nickel-base superalloys. For the first time, regression models are presented for calculating critical temperatures tп.р, tевт, tS, and tL which enable to predict temperature intervals of crystallization and homogenization.Practical value. An effective solution is proposed for prediction of thermodynamic stability of alloys phases both in the development of new compositions of nickel-base superalloys, as well as in the improvement of well-known industrial brands.

Influence of chemical composition of wear-resistant hard-facing materials on the tendency to formation of hot cracks during weld facing

Abstract At present, extreme cases of intercrystalline rupture at high temperatures in non-equilibrium crystallizing alloys (built-up layers) are clearly distinguished. Solidifying cracks are formed in enriched inter-axial and inter-dendritic areas at the moment when the latter are in a liquid state. This type of destruction is associated with crystallization of the last portions of the liquid phase enriched with low-melting alloying elements and impurities and is observed in alloys, where the second phase in the form of eutectics and chemical compounds is formed directly during the crystallization process. Subsolidus cracks, which are most often formed in single-phase alloys with a narrow temperature interval of crystallization, not in liquid intercrystalline interlayers, but after solidification of the last portions of the liquid phase, i.e. below the temperature of the real solidus.

Effect of Ti on structure and soft magnetic properties of Si-rich Finemet-type nanocrystalline Fe73.5Cu1Nb3-xSi17.5B5Tix alloys

Fe73.5Cu1Nb3-xSi17.5B5Tix (x = 0, 1, 2, 3) amorphous alloys were prepared by the single roller melt spinning method. The effects of Ti substitution for Nb on the crystallization behavior, microstructure and soft magnetic properties were investigated. Compared to the previously reported Finemet alloy, the onset primary crystallization temperature Tx1 becomes lower which has dropped from 803K to 758K. The crystallization temperature interval ΔTx increases from 468K to 488K as the x increases from 0 to 3. However, the Curie temperature of amorphous phase shows a downward tendency with the increase of Ti content. Compared to the previously reported Finemet alloy, the μi increases obviously to more than 18,000 at x = 1, the Hc decreases from 0.59 Oe to 0.54 Oe. When Ti replaces Nb completely, the optimum annealing temperature range for precipitating single soft magnetic phase is enlarged, but the permeability at room- and high-temperature is deteriorated, the reason of which was also analysed.

The Effect of Vanadium Content on Microstructure and Impact Toughness of Forged High Alloy Steel X96CrMo12-1

The aim of this research was to examine the influence of vanadium on the structure and impact toughness of the forged high alloy steel X96CrMo12-1. It is known that vanadium affects the process of solidification of this alloy by narrowing the temperature interval of crystallization. Vanadium, as an alloying element, moves liquids and solidus lines toward higher temperatures, approximately for 25–30 °C. In addition, vanadium forms V6C5 carbides, which are partly distributed between the present phases in the steel, carbide (Cr,Fe)7C3 and austenite. The presence of vanadium enables the formation of (Cr,Fe)23C6 carbide and its precipitation into austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite, i.e., vanadium reduces remained austenite and improves quenching process. Studies have shown that as the content of vanadium increases up to 5%, the impact toughness of this steel is significantly increased. The steel X96CrMo12-1 contains remarkably less carbon than high alloyed Cr–Mo ledeburite steels and does not contain a eutectic microconstituent in the structure. So it can be treated by forging process thus provide a more compact and tougher structure. The basic problem in the application of high alloyed Cr–Mo steels is to increase their impact toughness, while sustain a relatively high value of hardness. Studies have shown that vanadium strongly increases toughness while retaining high hardness, which is a requirement for wear-resistant steels.

The influence of the vanadium content on the toughness and hardness of high-alloyed Cr-Mo steel

Characteristics of air hardening steel are high hardness and low impact toughness. In order to increase the impact toughness while retaining replace with the high hardness value numerous research added. One of the ways to achieve this is the alloying of specified steel with vanadium and application of appropriate heat treatment. Vanadium affects the solidification process of these alloys by narrowing of the temperature interval of crystallization. In addition, vanadium formed V6C5 carbides that block the growth of austenitic dendrites and structure makes fine-grained. Vanadium which forms V6C5 carbides is partly distributed between present phases in the steel, carbide (Cr,Fe)7C3 and austenite. Also, the presence of vanadium can enable the formation of (Cr,Fe)23C6 carbide and its precipitation in austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite. In other words vanadium reduces the amount of remained austenite and so improves hardenbility of the steel. In this way, better technical characteristics of these steels are obtained.

Crystallization kinetics of rhyolitic melts using oxygen isotope ratios

AbstractCrystals provide the means to understand igneous systems, but natural constraints on crystallization kinetics are rare because thermal conditions and crystallization timescales are typically unknown. Oxygen isotope ratios in quartz and alkali feldspar crystals in spherulites provide a natural record of the temperature interval of crystallization and crystal growth rates in rhyolitic melts. Oxygen isotope compositions in both phases change progressively with position from the spherulite core to rim. Quartz δ18O increases from 5.0 ± 0.3‰ in the core to 5.6 ± 0.3‰ at the rims, whereas alkali feldspar decreases from 3.7 ± 0.4‰ in the core to 2.7 ± 0.9‰ at the rims. Fractionation therefore increases from 1.3 ± 0.7‰ in the cores to 2.9 ± 1.1‰ at the rims. Oxygen isotope thermometry tracks crystallization temperature with position. Spherulites nucleate at 578 ± 160°C and continue to grow until 301 ± 88°C. The in situ analyses demonstrate that spherulites self‐contain a record of their thermal history and that of the host lava.

Crystallization properties and thermal stability of polypropylene composites filled with wollastonite

The influence of wollastonite (CaSiO3) content on the crystallization properties and thermal stability of polypropylene (PP) composites was investigated. The results showed that the crystallization temperature, crystallization end temperature and crystallization temperature interval, as well as the degree of crystallinity of the composites, were higher than those of the unfilled PP resin, while the crystallization onset temperature was little changed from that of the unfilled PP resin. The increase of degree of crystallinity for the composites could be attributed to the heterogeneous nucleation of the CaSiO3 in the PP matrix. The thermal stability increased with increasing filler weight fraction (ϕf); the thermal decomposition rate decreased nonlinearly with increasingϕf. Finally, the dispersion of the filler particles in the matrix was observed, and the mechanisms of thermal stability and crystallizing behavior were discussed.

Influence of Vanadium Content on the Toughness and Hardness of High-alloyed Cr-Mo Steel

Characteristics of air hardening steel are high hardness and low impact toughness. In order to increase the impact toughness while retaining replace with the high hardness value numerous research added. One of the ways to achieve this is the alloying of specified steel with vanadium and application of appropriate heat treatment. Vanadium affects the solidification process of these alloys by narrowing of the temperature interval of crystallization. In addition, vanadium formed V6C5 carbides that block the growth of austenitic dendrites and structure makes fine-grained. Vanadium which forms V6C5 carbides is partly distributed between present phases in the steel, carbide (Cr,Fe)7C3 and austenite. Also, the presence of vanadium can enable the formation of (Cr,Fe)23C6 carbide and its precipitation in austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite. In other words vanadium reduces the amount of remained austenite and so improves hardenbility of the steel. In this way, better technical characteristics of these steels are obtained.

Crystalline properties of poly(L-lactic acid) composites filled with nanometer calcium carbonate

The poly(L-lactic acid) (PLLA) filled with nanometer calcium carbonate (nano-CaCO3) composites were prepared by means of a twin-screw extruder in the present paper. The nano-CaCO3 surface was treated with stearate. The crystalline properties of PLLA/nano-CaCO3 composites were measured using a differential scanning calorimeter, to identify the influence of the nanometer particle content on the crystalline properties. The results showed that the crystallization onset temperature, crystallization temperature and crystallization end temperature as well as the crystalline degree of the composites were obvious higher than those of the unfilled PLLA resin when the particle weight fraction (ϕf) was 1%, then they varied slightly. While the crystallization temperature interval decreased slightly. The improvement of crystallinity degree might be attributed to the heterogeneous nucleation of the nano-CaCO3 in the matrix.

Effects of Si addition on the crystallization behaviour of GeTe phase change materials

The effects of the addition of Si on the temperature dependence of the electrical resistance and crystallization temperature, Tx, of GeTe films were investigated by a two-point probe measurement. Tx of the (GeTe)100−xSix films increased with increasing Si content from x = 0 (188 °C) to x = 12.6 at% (297 °C). It was confirmed from XPS measurements that Si–Te bonds were formed in the (GeTe)100−xSix amorphous film by the addition of Si. The dependence of Si content on the Tx of the (GeTe)100−xSix film was calculated based on Lankhorst's model, which showed a linear relationship between Tx and the Si content. In the region of low Si content (x ⩽ 3.8 at%), the obtained result was in good agreement with the calculated result. Meanwhile, in the region of high Si content (x ⩾ 5.4 at%), the obtained result considerably deviated from the calculated line. This may be due to the formation of the strongest Si–Si bonds in the amorphous (GeTe)100−xSix film. It was found from XRD measurement that the (GeTe)87.4Si12.6 amorphous film showed crystallization with phase separation into α-GeTe and Si. The obtained results suggested that suitable Si content of the (GeTe)100−xSix film is in the range 3–7 at% because of the high Tx, a small temperature interval of crystallization and the absence of phase separation during crystallization.

The effects of initial welding temperature and welding parameters on the crystallization behaviors of laser spot welded Zr-based bulk metallic glass

This study investigated the effects of the initial welding temperature (IWT) and welding parameters on the crystallization behaviors of laser spot welded (Zr 53Cu 30Ni 9Al 8)Si 0.5 bulk metallic glass (BMG). After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's micro-hardness test. The results showed that the heat-affected zone (HAZ) crystallization seemed avoidable under the room temperature welding process. However, with a combination of a lower energy input (welding Condition C) and a lower IWT (at 0 °C), a crystallization-free HAZ was finally obtained. Using the above welding condition into the refined heat flow equation, a critical retention time of 79 ms for the crystallization temperature interval was estimated. Moreover, as the laser welded samples came to crystallization in the HAZ, it was observed that a higher content of spherical-type crystalline precipitates tended to result in a higher value of glass transition temperature, T g. Therefore, the GFA indices, Δ T x , γ and γ m, were reduced. Furthermore, it was found that the micro-hardness value in the HAZ crystallization area was decreased due to the massive cracks formed in most parts of the crystalline precipitates. For a crystallization-free HAZ, the hardness seemed unaffected.