Dilatometry Research Articles

Improvement in Casting Technology of the Blades of Aviation Gas-Turbine Engines Made of TNM-1B1 Alloy in Conditions of Induction Crucible Smelting

Properties of the TNM-B1 alloy based on γ-titanium aluminide are investigated in order to find reliable results of simulation of casting processes used to fabricate the blades of gas-turbine aircraft engines. Thermal properties of the TNM-B1 alloy are experimentally determined using the methods of differential scanning calorimetry (DSC), laser flash (LFA), and dilatometry (DIL). Various variants of gate-feeding systems for the production of cast blades using a smelting-pouring installation for vacuum induction smelting («Consarc», Scottland) in conditions of JSC Ufa Engine Production Association. The test casting is obtained and its defects are analyzed. Good correspondence of results of modeling to actual centrifugal pouring of blades is shown.

Effect of casting vacuum on thermodynamic and corrosion properties of Fe-based glassy alloy

The effect of casting vacuum on thermodynamic and corrosion properties of Fe61Co7Zr8Mo5W2B17 in shape of cylinder of 3 mm in diameter and ribbon of 20–40 μm in thickness and 2–3 mm in width were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), dilatometer (DIL), scanning electron microscopy (SEM) and electrochemical station. It is found that high casting vacuum can improve the glass forming ability (GFA), the contraction degree during heating, and the pitting resistance of the glassy alloy, which can be ascribed to the fact that the dissolution of tungsten in the melt is improved under the high casting vacuum.

Improvement in the casting technology of blades for aviation gas-turbine engines made of TNM-B1 titanium aluminide alloy produced by induction crucible melting

Properties of the TNM-B1 γ-titanium aluminide alloy are investigated in order to find reliable results of a simulation of casting processes used to produce the blades of gas-turbine aircraft engines. Thermal properties of the TNM-B1 alloy are experimentally determined using the methods of differential scanning calorimetry (DSC), laser flash analysis (LFA), and dilatometry (DIL). Various variants of gate-feeding systems for the production of cast blades using a vacuum induction melting furnace (Consarc, Scotland) in conditions of the Ufa Engine Production Association (OAO UMPO) are considered. The test casting is obtained and its defects are analyzed. A good correspondence of results of simulation to the actual centrifugal filling of blades is shown.

Using Electrical Resistivity Tomography (ERT) as a tool in geotechnical investigation of the substrate of a highway

Abstract Geological and geotechnical engineering field tests, like structure drillings and dynamic (DPL, DPSH) or static probing (CPT), are considered for a fundamental source of information about soil and water environments. Since Eurocode 7 has been introduced, it has become more common to use also dilatometers (DMT) or pressure meters (PMT). Results obtained using all the mentioned tests are always of a discrete nature - information is provided in certain points in the field. However, they determine the basis for creating spatial models of geological structure and geotechnical condi- tions of a substratum. The range and number of investigations conducted (including drilling, probing and laboratory tests) influence precision, in which a geological structure is identified and thus, also affect probability of compatibility between spatial model and real geological conditions of a substratum. In the paper, results of non-invasive electrical resistivity tomography (ERT) method are presented, comprising 2-dimensional image of a soil medium resistance. Electrical resistance is a parameter that reflects diversification of a soil medium, considering its lithological aspect. In addition, when combined with drilling results, it can be used to accurate determination of boundaries between soil layers. Carrying out of ERT tests in the field during expressway construction contributed to identification of weak, low-strength soils like organic soils (peat, aggradated mud) and of soft consistency cohesive soils. These kinds of soil are the main cause for unacceptable deformations appearing in the new road engineering structure.

Investigation on the Austenitic Reverse Transformation of 0.2C-3Mn-1.7Si Steel with an Ultra-Slow Heating Rate

In order to clarify the austenite reverse transformation of a 0.2C-3Mn-1.7Si steel during intercritical region with an ultra-slow heating rate of 0.05°C/s, DIL (dilatometer), SEM, XRD and EPMA were carried out. The experimental results indicated that the dilatometric cures exhibited the shape of two “valleys” and the growth of austenite from quenched martensite was composed of three consecutive sub-stages. This phenomenon is associated with Mn-rich and Mn-poor regions in martensite matrix. During the heat treatment,the austenite forms firstly in region enriched in Mn. However, with increasing temperature, the growth of γ is restrained owing to the concentration of Si. Upon the further process of heating, the free energy for the reverse transformation increases, and the residual Mn-depleted regions start to transform at a higher temperature.

Obtaining shape memory alloy thin layer using PLD technique

Copper-based shape memory alloy (SMA) was obtained through a classic melting method. The material was analyzed in heat treated and deformed states using scanning electrons microscopy (SEM), dilatometry (DIL), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and energy dispersive X-ray analyze (EDAX) to establish the material microstructure, memory properties like martensitic transformation domain and rate or damping capacity. The material exhibits a good shape memory effect and high internal friction and it is proposed as target in a pulsed laser deposition (PLD) process for obtaining thin films. The deposition process is described in this paper through presented experimental results on the layer.

Mechanical and thermal properties of hot pressed CoCrMo–porcelain composites developed for prosthetic dentistry

In this study, mechanical and thermal properties of CoCrMo–porcelain composites for dental restorations have been evaluated. These metal–ceramic composites were produced by powder metallurgy and hot pressing techniques from the mixtures of metal and ceramic powders with different volume fractions. Young's moduli and the coefficient of thermal expansion of materials were evaluated by dynamic mechanical analysis (DMA) and dilatometry (DIL) tests, respectively. The strength in flexion and shear was measured with a universal test machine and hardness with a respective tester. The microstructures and fracture surfaces were inspected by the means of optical microscopy and Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS).Shear strength, Flexural strength and Young' moduli of ceramic and metal-matrix composites were found to increase with higher metal particles content. The DMA tests performed at different frequencies showed no frequency-dependent features of the materials studied, indicating no viscoelastic behavior. The fracture surfaces analysis suggests the load-transfer mechanism be possibly responsible for this behavior, as the differences in CTE are low enough to cause significant thermal stresses in these materials. The results might be included in a materials properties database for further use for design and optimization of dental restorations.

Provenance study of Chinese proto-celadon in Western Han Dynasty

Abstract Provenance of Chinese proto-celadon during Shang-Zhou Period has been studied by a lot of scholars. There were two distinct opinions: some scholars claimed that all proto-celadon wares excavated in Northern China were manufactured in Southern China while others believed that both Southern and Northern did produce proto-celadon wares in the same period. Recently, an increasing number of researchers tend to support the viewpoint that proto-celadon has a multi-origin both in Southern China and in Northern China during this period. However, during Han Dynasty few proto-celadon wares and sherds were excavated in Northern China, it seems that all of the proto-celadon products found in Northern China came from Southern China. Several years ago, many huge proto-celadon wares were excavated in Rizhao Cemetery of Shandong Province, and some kilns and proto-celadon sherds were found in Cuipingshan site of Jiangsu Province. Both of the sites locate in Northern China and date to Western Han Dynasty. In this paper, the provenance study of the sherds from these two sites as well as those from Xiaolongjing Cemetery of Zhejiang Province were carried out by the use of dilatometer (DIL) and laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS). It was found that the northern sherds were fired at the temperature around 1200 °C, with higher Fe and Ca concentration but lower Mg content than southern ones, implying the unique manufacture craft in Northern China differing from the southern ones. Our results may suggest that Chinese proto-celadon produced in Western Han Dynasty has multiple producing regions not only in Southern China but also in the north.

Pencel Pressuremeter Testing to Determining P-Y Curves for Laterally Loaded Deep Foundations

Abstract The pressuremeter used was essentially the PENCEL pressuremeter (PPMT), manufactured by ROCTEST, Inc. This paper offers a description of the equipment, testing procedure, theory to obtain parameters of the ground and to develop the p-y curves for laterally loaded piles. From PPMT data reduced to graphs of pressure versus volume, soil parameters including the lift-off pressure, the initial elastic and reload moduli, and the limit pressure were determined. Methods developed to determine p-y curves from pressuremeter and dilatometer (DMT) test. P-y curves are used in the analysis to represent lateral soil-pile interaction. The pressuremeter offers an almost ideal in-situ modelling tool for determining directly the p-y curves for the design of deep foundations. As the pressuremeter can be driven into the soil, the results can be used to model a displacement pile. DMT tests were performed for comparisons with PPMT tests. Correlations were developed between the PPMT and DMT results, show consistency in soil parameters values. Comparison between PPMT and DMT p-y curves were developed based on the ultimate soil resistance, the slope of the initial portion of the curves, the shape of the curves. The initial slope shows a good agreement for this comparison. The predicted DMT and PPMT ultimate loads are not similar, while the predicted PPMT and DMT deflections within the elastic range are identical.

Sintering Behavior of Kaolin with Calcite

The study of sintering behavior of clay raw materials might be difficult because, as it is well known, these clays have a complex mineralogical composition, which causes a series of phase transformations occurring during sintering. Those processes relate to major and minor clay minerals (such as phyllosilicates, quartz, calcite, dolomite and hematite). Kaolinite is one of the main components of the clay. In this work, we consider sintering of kaolin, with different addition of pure calcite. The following techniques were used: differential thermal analysis (DTA), thermogravimetry (TG/DTG), dilatometry (DIL), heating microscope probe and X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, comparisons between the microstructure of the sintered bodies and their physical- mechanical properties have been made.

Element-specific study of local segmental dynamics of polyethylene terephthalate upon physical aging

Time-dependent relaxation processes upon physical aging below the glass transition temperature have been studied in polyethylene terephthalate by high-precision dilatometry (DLT), differential scanning calorimetry (DSC), and element-specific positron and positronium (Ps) annihilation spectroscopy. The macroscopic volume change observed by DLT can be described by the Kohlrausch-Williams-Watts decay function, whereas changes in the relaxation enthalpies evaluated by DSC and free volumes probed by positron and Ps annihilation spectroscopy are reproduced by two superimposed exponentials. The multi-method approach reveals three kinds of relaxation processes with characteristic relaxation times: (a) fast Arrhenius-type β relaxation involving the instantaneous local segmental densification along with the exclusion of oxygen atoms from free volumes, (b) macroscopically observable non-Arrhenius-type α relaxation originated from a distribution of relaxation times due to the heterogeneous dynamics of solid-state- and liquid-state-like local segments, and (c) extremely slow Arrhenius-type α relaxation as the consequence of a uniform relaxation time solely due to the thermal dependence of nanometer-scale solid-state-like local segments.

Densification Dynamics of Gadolinium-Doped Ceria upon Sintering

Densification behavior upon sintering is studied for gadolinium-doped ceria (GDC) by making use of X-ray diffraction, Archimedes method, high-resolution dilatometry (DLT), and element-specific positron annihilation spectroscopy. We found high concentration of vacancy-like nano-defects at GDC-crystallite interfaces participating in densification. Time-resolved length change and positron lifetime measurements enable to discuss the densification dynamics at the particle boundary relevant to a sintering neck and inside the particles. The particle boundary largely contributes to densification at the initial stage of sintering, whereas the crystallite interface gets to be responsible for prolonged densification. The densification inside the particle is developed by the growth of the crystallites followed by the transfer of Gd atoms from the interfaces to the crystallites.

Influence of compression on thermal and corrosion behavior of Fe 78Si 9B 13 glassy alloy

The Fe 78Si 9B 13 glassy ribbons were compressed at room temperature with different pressures. The thermal and corrosion behaviors were investigated using various experimental techniques. The X-ray diffraction (XRD) and dilatometer (DIL) results show that the Fe 78Si 9B 13 ribbons are in full amorphous state after pressing and the amount of free volume increases monotonically with increasing pressure. The corrosion resistance of the glassy alloys in various solutions decreases after compression at 10 MPa, but increases after compression at 20 MPa. The non-monotonic change of corrosion resistance is consistent with the result of electrical resistivity, which can be explained by the combining action of free volume that is introduced by the compression and the segregation of Si atoms in the samples.

Finite element sintering analysis of metal injection molded copper brown body using thermo-physical data and kinetics

A finite element analysis based on a thermo-kinetic model was established to describe the densification process of a MIM copper brown body during sintering. This finite element analysis does not require a constitutive law; rather the thermo-physical data (density, thermal conductivity, specific heat as a function of temperature) and kinetics are used to predict sintering deformation. The thermo-physical data were obtained by measuring the brown MIM copper compacts using dilatometer (DIL), laser flash (LFA) and differential scanning calorimeter (DSC). These aspects are included in our work with emphasis on the development of a numerical model which is made possible by the commercial finite element software ANSYS@. To verify the densification-based finite element method, two case studies are made and discussed. The numerical predictions were compared with experimental measurements, and it is shown that the results numerically simulated by FE agree well with those experimentally observed by furnace sintering. Furthermore, some enhancements are suggested in temperature field calculation of FE model in order to draw a real furnace conditions.

Precipitation in AlCu4.3 and AlCu4Mg alloys studied by dilatometry and calorimetry

Precipitation in AlCu4.3 and AlCu4Mg alloys studied by dilatometry and calorimetry

Estudo de fundentes alternativos para uso em formulações de porcelanato

O porcelanato tem se destacado no mercado atual de revestimentos cerâmicos, pois apresenta excelentes características técnicas e estéticas. Neste trabalho foram selecionadas matérias-primas cerâmicas tradicionais e adotada uma formulação padrão convencionalmente reportada na literatura, visando à substituição da fase fundente (feldspato) da composição por dois tipos de matérias-primas formadoras de fase líquida em alta temperatura. O objetivo foi avaliar essas matérias-primas como alternativas técnicas e de menor custo, uma vez que, em uma massa de porcelanato, a quantidade de fundente é muito grande, e representa aproximadamente 50% do total das matérias-primas utilizadas. A nefelina sienito foi a matéria-prima natural substituta escolhida por pertencer à família dos feldspatóides e que possui características físico-químicas semelhantes ao feldspato, portanto, uma elevada fundência. O segundo fundente foi um material sintético, denominado fluxo, com características físico-químicas bem diferentes e uma fundência ainda maior. A substituição ao feldspato ocorreu de maneira total e/ou parcial, por meio de combinações entre os fundentes alternativos. As massas foram processadas a partir da mistura de pós, moagem a úmido, secagem, desaglomeração, compactação e queima. Além das curvas de gresificação, técnicas como sedimentometria, dilatometria, medidas de porosidade aparente, ensaio de resistência mecânica à flexão a três pontos, microscopia eletrônica e difratometria de raios X foram utilizadas para a caracterização dos materiais após queima em diversas temperaturas. Os principais resultados mostraram que, a princípio, é possível a combinação das matérias-primas nefelina e fluxo como material alternativo ao feldspato, pois elas proporcionam a gresificação em temperaturas mais baixas. Composições com ambos fundentes apresentaram baixos valores de absorção de água (< 0,1%) e elevada resistência mecânica (45 MPa) quando comparadas a padrão, apesar de maior deformação piroplástica. A presença da nefelina não altera qualitativamente a formação de fases e o fluxo gera novas fases cristalinas.

Alloyed W–(Co,Ni,Fe)–C phases for reaction sintering of hardmetals

It has been shown that W–Co–C phases could dissolve a substantial amount of metals such as V, Cr and Ta, which are known to positively influence the microstructure of hardmetals with respect to uniform grain size distribution and fine grain size. This offers a tool to circumvent the conventional doping of hardmetals with individual carbides. In the present study we used double- and triple-alloyed κ-W9Co3C4 (i.e. κ-(W,V,Cr)9Co3C4 and κ-(W,V,Cr,Ta)9Co3C4) and applied a variety of sintering experiments to obtain WC–Co, WC–(Ti,Ta,Nb)C–Co and WC–(Ti,Ta,Nb)(C,N)–Co hardmetals. We also prepared κ-W9Fe3C4, alloyed κ-W9Ni3C4, and κ-W9(Fe/Ni)3C4, and used the latter for sintering. Sintering was studied in situ by mass spectrometric outgassing experiments (MS-EGA) and dilatometry (DIL). The reactively-sintered hardmetals can be obtained with a very low amount of platelets and show the same properties as hardmetals with platelets. The latter are obviously not responsible for the high KIc values in these hardmetals. The alloy status of the starting alloyed κ-W9Co3C4, especially a certain amount of Ta, plays a role in WC grain growth for avoiding platelets. The good KIc is most probably due to a uniform Co distribution (the binder phase and WC form simultaneously by reaction of κ phase with C. Upon this formation, V, Cr and Ta are directly involved, because they are dissolved in the κ phase). The influence of the starting grain size of alloyed κ-W9Co3C4 on the grain size of reactively sintered hardmetal is crucial. This is probably due to the short diffusion distance of C, which causes the formation of very fine WC particles upon reaction with C. Together with alloyed κ-W9Co3C4, oxides were used to form fcc carbides by in situ carburisation. The microstructure of such prepared WC–(Ti,Ta,Nb)C–Co hardmetals is finer and the interpenetration of the WC and fcc particles is better than by use of fcc carbides in the starting mixture. The same is true if nitrogen atmosphere is used (and C level in the starting formulation is reduced) to form WC–(Ti,Ta,Nb)(C,N)–Co hardmetals. With respect to the fracture toughness/hardness relationship, some of the prepared hardmetal grades show better properties than industrial grades and could thus possibly outperform the latter in cutting applications.

Redox Properties of Ni-YSZ Anodes

The NiO-YSZ composites with 30wt%, 50wt.% and 70wt.% NiO were investigated by the temperature programmed reduction (TPR), scanning electron microscope (SEM) and dilatometer (DIL) methods. The NiO in the sintered sample with higher content of NiO shows highest activity towards reduction. After re-oxidation at 800oC, the main reduction peak temperature is not clearly dependent on the NiO content, the higher temperature can accelerate the aggregation of NiO more obviously and make the formed NiO particles have lower activity during re-oxidation. The thermal expansion coffient increases with the increasing of NiO content, which is due to the higher TEC of NiO and the high contribution of NiO to the framework of composite.

Correlation between microstructure and thermal dilation behavior of amorphous Fe-Co-Zr-Mo-W-B alloys

The microstructures and thermal properties of Fe 61Co 9− x Zr 8Mo 5W x B 17 ( x = 0 and 2) formed under different vacuum conditions were investigated by scanning electron microscopy(SEM), X-ray diffractometry(XRD), transmission electron microscopy(TEM), and conventional dilatometry(DIL). The variation of the non-monotonic effects of tungsten content and vacuum conditions on the glass forming ability(GFA) of Fe-based alloys can be drawn in a schematic diagram. The higher the GFA of alloys, the higher the difference between the thermal expansion coefficients of glassy state and crystalline state(Δ α), which can be described by the free volume model during dilatometric measurements. Under low and high vacuum conditions, the viscosity and microhardness are improved and the fragility of the Fe-based alloys are decreased by adding tungsten.

Factors Influencing the Reversion of Stress-induced Martensite to Austenite in a Fe-Mn-Si-Cr-Ni Shape Memory Alloy

It is well known that one way shape memory effect (SME) in Fe-Mn-Si-based shape memory alloys (SMAs) is related to the thermally induced reversion of e (hexagonal close packed, hcp) stress-induced martensite (SIM) to γ (face centered cubic, fcc) austenite. In the case of a Fe-Mn-Si-Cr-Ni SMA, this reverse martensitic transformation was analyzed in regard to the critical temperature for the beginning of austenite formation (As) in different states characterized by quenching temperature and permanent tensile strain. For this purpose, dynamic mechanical analysis (DMA), dilatometry (DIL), differential thermal analysis (DSC), and optical microscopy (OM) were employed to determine the influence of quenching temperature and permanent tensile straining on SIM reversion to austenite during heating.