High-temperature Form Research Articles

Experimental study on fire characteristics of urban rectangular tunnels based on different slopes

Abstract To explore the combustion pattern and temperature distribution law of urban rectangular tunnels when a fire occurs. Considering the influence of variables such as different firepower, fire source spacing, and tunnel slope, the vertical and horizontal flame combustion patterns and tunnel temperature distribution of double fire sources under different slopes were studied by the indoor model experiment method. The results show that under the same conditions of the fire source spacing ratio μ, when the slope of a rectangular tunnel is between 0% and 3%, the influence of dual flames combustion morphology on tunnel slope is relatively small; When the tunnel slope is 4% to 5%, that has a significant impact on the combustion morphology of dual flames, and the flames are more dispersed and sparse than the tunnel slope is between 0% and 3%. As the tunnel slope increases, a high-temperature zone forms at the top of the tunnel and gradually moves towards the uphill direction of the tunnel, the high-temperature area gradually decreases as the slope increases with the same μ. The research results provide a theoretical basis for the fire protection design standards and fire prevention measures of urban rectangular tunnels.

Liquid and crystallized phases stability in the sub-system H3PO4[sbnd]H4P2O7: Experimental determination and modeling

The study of the system formed by ortho- and pyrophosphoric acid was resumed in order to understand the crystallization conditions of these two compounds and to highlight the existence of their possible polymorphism. To this end, the solid-liquid equilibria (SLE) of pyrophosphoric acid was studied in depth. Contradictions in literature data were resolved through systematic experimentation: solubility measurements, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Calorimetric measurements confirmed the existence of two crystalline forms of pyrophosphoric acid, and their stability domains were determined. Furthermore, thermodynamic modeling of the SLE has led to a consistent and refined representation of the observed phenomena. In particular, the transition temperature from low-temperature (form I) to high-temperature form (form II) of pyrophosphoric acid was determined at 298.4 K and the coordinates of the eutectic point common between H3PO4 and H4P2O7 (I) were precisely determined. Modeling also confirms the non-negligible quantity of triphosphoric acid in the liquid state throughout virtually the entire compositional range. Finally, X-ray powder diffraction data were used to determine the cell parameters and space group of pyrophosphoric acid using EXPO 2014 software.

Revisiting the thermodynamic properties of the ZrCr2 Laves phases by combined approach using experimental and simulation methods

A comprehensive study of ZrCr2 Laves phases is important for both fundamental research and technological applications. The ZrCr2 compound is a typical precipitate observed in Zr-based alloys including the newly developed Cr-coated Zr cladding known as Accident Tolerant Fuel cladding. The brittle behavior of the Laves phases and the low melting point at the interface zone between the precipitates and the Zr matrix are considered as governing the thermomechanical behaviors of these newly developed nuclear fuel claddings for normal operating conditions but more dramatically in case of Loss Of Coolant Accident (LOCA) conditions. The aim of the present study is to investigate the various ZrCr2 Laves polymorphs and their thermodynamic features particularly where conflicts exist in the literature. Based on diffraction experiments of annealed samples, it has been established that the transformation from the C14 high-temperature form to the C15 low-temperature form is of displacive nature without the C36 polymorph forming as an intermediate phase. The stable and metastable domains of C14 and C15 and their thermodynamic properties have been determined. The specific heat of both C14 and C15 types was measured over a wide range of temperatures from 2 to 1063 K by coupling relaxation calorimetry and DSC. The experimental data were fitted using a modified Einstein model. The room temperature entropies of the C14 and C15 phases were evaluated. The enthalpy of formation was measured for the first time using drop solution calorimetry in liquid Al at 1173 K in a Tian–Calvet calorimeter. The experimental value is in good agreement with Density Functional Theory (DFT) calculations. Finally, all these new results are discussed regarding the abundant literature on the ZrCr2 Laves phases.

High-Resolution 17O Solid-State NMR as a Unique Probe for Investigating Oxalate Binding Modes in Materials: The Case Study of Calcium Oxalate Biominerals.

Oxalate ligands are found in many classes of materials, including energy storage materials and biominerals. Determining their local environments at the atomic scale is thus paramount to establishing the structure and properties of numerous phases. Here, we show that high-resolution 17O solid-state NMR is a valuable asset for investigating the structure of crystalline oxalate systems. First, an efficient 17O-enrichment procedure of oxalate ligands is demonstrated using mechanochemistry. Then, 17O-enriched oxalates were used for the synthesis of the biologically relevant calcium oxalate monohydrate (COM) phase, enabling the analysis of its structure and heat-induced phase transitions by high-resolution 17O NMR. Studies of the low-temperature COM form (LT-COM), using magnetic fields from 9.4 to 35.2 T, as well as 13C-17O MQ/D-RINEPT and 17O{1H} MQ/REDOR experiments, enabled the 8 inequivalent oxygen sites of the oxalates to be resolved, and tentatively assigned. The structural changes upon heat treatment of COM were also followed by high-resolution 17O NMR, providing new insight into the structures of the high-temperature form (HT-COM) and anhydrous calcium oxalate α-phase (α-COA), including the presence of structural disorder in the latter case. Overall, this work highlights the ease associated with 17O-enrichment of oxalate oxygens, and how it enables high-resolution solid-state NMR, for "NMR crystallography" investigations.

High-temperature all-solid-state batteries with LiBH4 as electrolyte – a case study exploring the performance of TiO2 nanorods, Li4Ti5O12 and graphite as active materials

Abstract The hexagonal high-temperature form of LiBH4 is known as a fast ion conductor. Here, we investigated its suitability as a solid electrolyte in high-temperature all-solid-state cells when combined with the following active materials: Li metal, graphite, lithium titanium oxide (Li4Ti5O12, LTO), and nanocrystalline rutile (TiO2). First results using lithium anodes and rutile nanorods as cathode material show that a cell constructed by simple cold-pressing operates at reversible discharge capacities in the order of 125 mA h g−1 at a C-rate of C/5 and at temperatures as high as 393 K. Besides TiO2, the compatibility of the LiBH4 with other active materials such as graphite and LTO was tested. We found evidence of possible interface instabilities that manifest through rare, yet still detrimental, self-charge processes that may be relevant for hydrogen storage applications. Moreover, we investigated the long-term cycling behavior of the cells assembled and demonstrate the successful employment of LiBH4 as an easily processable model solid electrolyte in practical test cells.

High-temperature oxidation characteristics of 20CrMnTi electroplated with copper

During high-temperature forming and phase change heat treatment, the steel surface is susceptible to oxidation. This can negatively affect the surface quality of steel parts. The production of antioxidant coatings on the surface of steel parts is important for high-temperature precision forming and heat treatment. In this paper, the high-temperature oxidation tests of 20CrMnTi steel, copper, and 20CrMnTi electroplated with copper are conducted. The 20CrMnTi samples showed varying degrees of mass gain above 900 °C; the copper samples showed varying degrees of mass gain above 700 °C; and the process of mass gain for copper-plated 20CrMnTi followed the same trend as for copper during heating and holding. For heated samples of 20CrMnTi plated with copper, the copper coating was oxidized and residual copper was observed in the oxide layer. The distance between the residual copper and the surface of the sample is greater than between the residual copper and the junction of the plating layer and the substrate. Oxygen diffuses through internal defects in the material at a higher rate than copper oxidation. In this study, an oxygen diffusion model and an antioxidant protective layer model at high temperatures were suggested. The protective layer against oxidation recommended in this research is a dense coating consisting of single crystals or fine grains free of porosities and cracks.

Structural Phase Transitions in the Double Salts (NH4)2PO3F·NH4NO3 and (NH4)2XO4·3NH4NO3 (X = Se, Cr)

In the context of investigating isostructural relationships between sulfates and monofluorophosphates, crystals of the double salts (NH4)2PO3F·NH4NO3 (AFP·AN) and (NH4)2XO4·3NH4NO3 (AX·3AN; X = Se, Cr) were grown from aqueous solutions and structurally characterized using X-ray diffraction and thermal analysis. Whereas the high-temperature forms of the two AX·3AN double salts are in fact isostructural with the sulfate analogue, AFP·AN crystallizes with a reduced amount of NH4NO3 and thus has a unique crystal structure. Both AFP·AN and the two AX·3AN compounds exhibit reversible structural phase transitions. Upon cooling, the monofluorophosphate double salt transforms from the monoclinic room-temperature polymorph (I; P21/n, Z = 4) to the intermediate triclinic polymorph (II; P1, Z = 4) that in turn transforms to the monoclinic low-temperature polymorph (III; P21/n, Z = 4). The two phase transitions (I) → (II) and (II) → (III) are characterized by a significant increase of the unit cell volumes upon cooling. The two AX·3AN double salts transform upon cooling from a disordered monoclinic crystal structure (P21, Z = 2) to a monoclinic polymorph with a doubled unit cell (P21/c, Z = 4). Such a phase transition is not observed for the sulfate analogue. All molecular moieties are fully ordered at −93 °C for the selenate double salt, whereas one of the nitrate anions remains disordered for the chromate double salt even at −173 °C. In all AFP·AN and AX·3AN crystal structures, the nitrate anions play a crucial role during the phase transitions, and an extensive network of N–H···O hydrogen-bonding interactions is responsible for the cohesion of the crystal.

Effect of Microstructure Change on Mechanical Properties after High Temperature Forming of Ti-6Al-4V Alloy

Ti-6Al-4V alloy is not easy to machine complicated shapes due to its low thermal conductivity, so high-temperature forming techniques such as ring-rolling are being applied. When this high-temperature forming technology is applied, the microstructure is greatly changed by process variables, and the mechanical properties of the forming product are also different accordingly. In particular, in the case of the Widmanst tten structure, α lamellar spacing and colony size have a great influence on mechanical properties. Therefore, in this study, the most suitable process conditions were selected by performing a high-temperature compression test to apply the ring-rolling process to the Ti-6Al-4V alloy used as an aerospace material. After that, the microstructure of the forming product was observed, the effects of α lamellar spacing and colony size on the mechanical properties were confirmed, and the correlation between mechanical properties and microstructure was evaluated based on this.

Thermal stability of the CuZrSe2

The CuZrSe2 compound was synthesized for the first time by intercalation of Cu into the ZrSe2 lattice at room temperature. Experimental study of the thermal stability of CuZrSe2 has been performed by in-situ temperature-dependent synchrotron radiation X-ray diffraction (SR-XRPD). CuZrSe2 has a layered structure with space group P3‾m1. The copper atoms at room temperature in the interlayer space are octa- and tetrahedrally coordinated by selenium. Heating leads the decomposition of the main layered phase into binary copper chalcogenides and zirconium trichalcogenide as previously shown for CuxZrTe2. With the increase in temperature the octahedral sites in main layered phase become empty, copper atoms occupy the tetrahedral sites only. Thus, the high-temperature form of CuZrSe2 has a delafossite-like structure.

Fast heating inhibits endothermic solid-solid polymorphic transition giving a melting of low temperature polymorph with the next cold crystallization

Heating at the rate of several hundred Kelvin per second in fast scanning calorimetry (FSC) experiments was found to change the route of polymorphic transformation. Upon the increase of the heating rate first the endothermic solid-state polymorphic transition is hindered to give a consecutive melting of low-temperature form and crystallization of high temperature polymorph. At higher heating rates, only melting of low-temperature polymorph is observed much below an equilibrium melting point. This thermal behavior with depression of final melting point by 30 K was observed for tert‑butylthiacalix[4]arene tetrasubstituted with (ethoxycarbonyl)methoxy groups (1), which does not sublimate at heating. A similar shift of the endothermic solid-state polymorphic transition by temperature at fast heating was found for caffeine (2), however the melting of low-temperature polymorph is not observed due to sublimation of the compound at elevated temperatures. The heating rates, at which a significant depression of the melting points of 1 and 2 may be expected in absence of sublimation, were calculated using equations of thermal kinetics derived from the data of conventional differential scanning calorimetry. The results give a practical guide for the preparation of glassy forms of the substances capable of endothermic solid-solid transition below melting point of high-temperature form.

Fluid–solid coupled simulation of hypervelocity impact and plasma formation

Previous theoretical and computational studies on hypervelocity impact have mainly focused on the dynamic response of the solid materials that constitute the projectile and the target, while the surrounding environment is often assumed to be a vacuum. In this paper, we consider impact events that occur in a fluid (e.g., gas) medium, and present a computational model that includes the dynamics, thermodynamics, and ionization of the surrounding fluid material. The model couples the compressible Navier–Stokes equations with the Saha equations to predict the onset and extent of ionization in the surrounding fluid. An extended level set method with two signed distance functions is employed to track the three material interfaces between the projectile, the target, and the ambient fluid. This method accommodates the large deformation, contact, and separation of the interfaces, while avoiding spurious overlapping of different material subdomains. The advective fluxes across material interfaces are computed by constructing and solving bimaterial Riemann problems, thereby taking into account the discontinuities in both state variables (e.g., density) and thermodynamic relations. The computational model is first verified for an infinite ideal plasma and a one-dimensional three-material impact problem. Next, the model is employed to analyze the impact of a tantalum rod projectile onto a soda lime glass (SLG) target in an argon gas environment. In different analyses, the impact velocity is varied between 3 and 6km/s, and the radius of the projectile is varied between 2.5 and 10mm. Each analysis starts with a steady-state fluid dynamics simulation that generates the shock-dominated hypersonic flow around the projectile. This flow field is then used as an initial condition to start the fluid–solid coupled impact simulation. The predicted maximum temperature and pressure within the SLG target agree reasonably well with published experimental data for a similar material (fused quartz). Within the ambient gas, the impact-generated shock wave is found to be stronger than the initial bow shock in front of the projectile. Behind this shock wave, a region of high pressure and temperature forms in the early stage of the impact, mainly due to the hypersonic compression of the fluid between the projectile and the target. The temperature within this region is significantly higher than the peak temperature in the solid materials. For impact velocities higher than 4km/s, ionization is predicted. This finding indicates that the ambient gas may be a nontrivial contributor to the plasma formed in terrestrial and atmospheric hypervelocity impact events.

Exploring the Supramolecular Interactions and Thermal Stability of Dapsone:Bipyridine Cocrystals by Combining Computational Chemistry with Experimentation.

The application of computational screening methodologies based on H-bond propensity scores, molecular complementarity, molecular electrostatic potentials, and crystal structure prediction has guided the discovery of novel cocrystals of dapsone and bipyridine (DDS:BIPY). The experimental screen, which included mechanochemical and slurry experiments as well as the contact preparation, resulted in four cocrystals, including the previously known DDS:4,4'-BIPY (2:1, CC44-B) cocrystal. To understand the factors governing the formation of the DDS:2,2'-BIPY polymorphs (1:1, CC22-A and CC22-B) and the two DDS:4,4'-BIPY cocrystal stoichiometries (1:1 and 2:1), different experimental conditions (such as the influence of solvent, grinding/stirring time, etc.) were tested and compared with the virtual screening results. The computationally generated (1:1) crystal energy landscapes had the experimental cocrystals as the lowest energy structures, although distinct cocrystal packings were observed for the similar coformers. H-bonding scores and molecular electrostatic potential maps correctly indicated cocrystallization of DDS and the BIPY isomers, with a higher likelihood for 4,4'-BIPY. The molecular conformation influenced the molecular complementarity results, predicting no cocrystallization for 2,2'-BIPY with DDS. The crystal structures of CC22-A and CC44-A were solved from powder X-ray diffraction data. All four cocrystals were fully characterized by a range of analytical techniques, including powder X-ray diffraction, infrared spectroscopy, hot-stage microscopy, thermogravimetric analysis, and differential scanning calorimetry. The two DDS:2,2'-BIPY polymorphs are enantiotropically related, with form B being the stable polymorph at room temperature (RT) and form A being the higher temperature form. Form B is metastable but kinetically stable at RT. The two DDS:4,4'-BIPY cocrystals are stable at room conditions; however, at higher temperatures, CC44-A transforms to CC44-B. The cocrystal formation enthalpy order, derived from the lattice energies, was calculated as follows: CC44-B > CC44-A > CC22-A.

Fine-grained aluminium crossover alloy for high-temperature sheet forming

This study presents age-hardenable, fine-grained AlMgZnCu crossover alloys intended for superplastic and quick plastic forming processes. The study utilizes T-phase (Mg32(Al,Zn)49) for both grain refinement and age-hardening. It deploys a uniform distribution of µm-sized T-phase particles, which can be dissolved upon final solution annealing, and which is utilized for heavy particle stimulated nucleation (PSN) during industrial processing of sheets, in order to reach an equiaxed grain size as low as 4 µm. This fine grain size is advantageous for high-temperature forming of aluminium alloys. Elongations above 200% and 400% are achieved when deformed at strain rates of 10−2 s−1 or 5*10−5 s−1 at 470 °C, and interestingly, the fine grain structure is highly stable even when held at that temperature for one day. Moreover, the material reached yield strength values of more than 380 MPa after a paint-bake heat treatment for quenching in water or compressed air. The study demonstrates the importance of PSN using electron microscopic and texture measurements and describes it by simple modelling of T-phase particle grain refinement. It explores the high stability of the fine grain assembly in terms of the random grain boundary misorientation distribution in combination with high solute content observed, provided via the dissolved T-phase, and Smith-Zener pinning. The simple, commercially available grain refinement strategy demonstrated using the dissolvable T-phase, and the resulting unique property profile, make the crossover alloy in question a promising candidate for high-temperature sheet forming processes.

Modelling of methane sorption enhanced reforming for blue hydrogen production in an adiabatic fixed bed reactor: unravelling the role of the reactor's thermal behavior

Methane sorption enhanced reforming (SER) is investigated in this work as a promising route for blue H2 production. A 1-D dynamic heterogeneous model is developed to evaluate the thermal behavior of a fixed bed reactor under adiabatic conditions. The heterogeneous model allows to decouple the feed gas temperature from the initial solid one in order to investigate the behavior of the reforming step in a temperature swing reforming/regeneration process. The effects of the feed gas temperature, the initial bed temperature, and the bed thermal capacity are studied by evaluating the global impact of each parameter through a set of key performance indices (CH4 conversion, H2 yield and purity, carbon capture ratio) calculated as integrals over the duration of the reforming step. The results highlight the minor effect of the initial bed temperature on the process performances showing the potential of minimizing the extent of a cooling step between regeneration and reforming stages. Besides, due to the endothermic nature of the methane sorption enhanced reforming process at high temperatures, thermal energy must be provided to the SER process to achieve high CH4 conversion and high carbon capture ratio. This can be made either in the form of high feed temperature or by utilizing the energy stored in the bed benefiting from the bed thermal capacity.

The polymorph landscape of dabigatran etexilate mesylate: Taking the challenge to bring a metastable polymorph to market

Dabigatran etexilate mesylate is polymorphic and can exist in different crystalline forms. Two polymorphs have been encountered during the development of this drug substance, namely anhydrous form I and anhydrous form II. Additionally, a hemihydrate was observed, if larger amounts of water were present during crystallization in the salt formation step. Finally, a high temperature form III can be obtained by heating anhydrous form I above 150 °C. All three at room-temperature accessible forms were characterized by means of microscopy, X-ray powder diffraction, thermal analysis, IR- and Raman spectroscopy. In addition, solubility parameters (equilibrium solubility and intrinsic dissolution rate, heat of solution) were collected on all three forms. The crystal structure of all three at room-temperature accessible forms could be obtained using electron diffraction. Anhydrous form I has a monoclinic crystal lattice (C2/c), anhydrous form II a triclinic one (P1¯), and the hemihydrate crystallizes also in a monoclinic space group (P2/c). From the obtained data there is clear evidence that anhydrous form II is thermodynamically more stable than anhydrous form I. Form I and form II are monotropically related to each other indicating that they may coexist over a wide temperature range. The hemihydrate is a completely independent crystalline modification of dabigatran etexilate mesylate. It is another thermodynamically stable form and structurally not related to the two anhydrous forms. The hemihydrate melts at ca. 125 °C, there is no conversion to either anhydrous form I or form II upon dehydration. The high temperature form III is enantiotropically related to form I and only stable above the phase transition temperature at ca. 150 °C and its melting point at ca. 183 °C. The energy difference between anhydrous form I and form II was found to be only 2.5 – 3.0 J/g. Both forms have very similar aqueous solubility characteristics. Although anhydrous form II is the thermodynamically more stable form, anhydrous form I was chosen for development. The selection of form I for development was mainly based on the superior bulk processing properties of anhydrous form I in drug substance synthesis and further drug product processing as well as its slightly better chemically stability in pivotal long term stability studies. Anhydrous form I, although meta stable, is still stable enough that conversion to the more stable form II can occur only to a limited extent during drug substance synthesis and drug product manufacturing. From long term stability data on both bulk drug substance as well as drug product, there is no indication that form I transforms to form II during storage. Even under stress conditions where form I was stored up to 4 weeks at 70 °C, no conversion to form II was observed.

Laser metal deposition of self-lubricating alloys on selective laser melting maraging tools for the high temperature forming of aluminium

Selective laser melting (SLM) is an additive manufacturing technique that allows the layer-by-layer fabrication of metallic components with high dimensional tolerances, being also particularly suitable for implementing complex geometries such as cooling channels in hot forming tools. However, high temperature forming processes pose severe conditions that often require additional surface protection and functionality. The present work proposes to increase the lifetime and endurance of SLM tools using self-lubricating coatings deposited by laser metal deposition (LMD). To this end, 3D printed samples made of maraging steel prepared by SLM are functionalized with self-lubricating coatings applied by LMD. Two different metallic alloys are deposited, a nickel-based alloy containing metal sulphides and silver, and an iron-based alloy containing graphite. The resulting microstructure after the hybridization of both additive manufacturing techniques has been thoroughly analysed in terms of the microstructural changes. Afterwards, the functionalized 3D printed tools are investigated for prospective high temperature sheet metal forming of aluminium alloy AA6082 using a ring compression test rig at 300 °C, using a reference hot work tool steel as reference. The results show that the use of Ni-based self-lubricating coatings contributes to a more stable frictional behaviour, independently of the dilution of the externally added lubricant. These results serve as example for the enormous potential for the combination of laser metal deposition with selective laser melting for tool functionalization.

Observation of multigap and coherence peak in the noncentrosymmetric superconductor CaPtAs: As75 nuclear quadrupole resonance measurements

We present synthesis and $^{75}$As-nuclear quadrupole resonance (NQR) measurements for the noncentrosymmetric superconductor CaPtAs with a superconducting transition temperature $T_c$ of $\sim 1.5$ K. We discovered two different forms of CaPtAs during synthesis; one is a high-temperature tetragonal form that was previously reported, and the other is a low-temperature form consistent with the orthorhombic structure of CaPtP. According to the $^{75}$As-NQR measurement for superconducting tetragonal CaPtAs, the nuclear spin-lattice relaxation rate $1/T_1$ has an obvious coherence peak below $T_c$ and does not follow a simple exponential variation at low temperatures. These findings indicate that CaPtAs is a multigap superconductor and a large $s$-wave component.

High-speed superplastic formability and deformation mechanisms of Ti6Al4V sheets

A low deformation rate is a significant disadvantage in the high-temperature superplastic forming (SPF) process, and grain boundary sliding (GBS) and creep mechanisms occur during deformation. The high-speed SPF method is being investigated to eliminate this disadvantage. Also, the high-speed SPF of Ti6Al4V (Ti64) sheet material and the effects of deformation mechanisms on formability were investigated experimentally. SPF and high-speed SPF treatments were carried out with hot tensile tests at specific temperatures, which in turn are 670, 770, 870, 890, and 910 °C at deformation rates of 10-2 to 10-3 s-1 and without a protective atmosphere. The deformation mechanisms in the microstructure of the samples were investigated by electron microscopy. In experimental studies, it has been observed that GBS deformation occurs at 870 °C and positively affects formability with 1489% elongation at 870 °C and 701% at 910 °C. While the effects of these deformation mechanisms were not observed clearly under 870 °C, it was observed that the superplastic formability had a decreasing trend at 890 °C and 910 °C with the effect of creep deformation.

On the polymorphism of La2SiMoO8: New metastable high temperature forms and NTE (negative thermal expansion) phase transitions

Following a previous study on scheelite LT-La2SiMoO8, a new high temperature polymorph was discovered after metastabilization down to room temperature (HT). An attempt at structural determination by neutron diffraction led to large atomic displacement parameters of the Mo cation and/or of some of its oxygen neighbors, suggesting structural instability. It was confirmed by thermal analysis and X-ray thermodiffraction, showing the existence of a phase transition at 440 ​°C between two very close polymorphs, probably mixed in the HT sample. The structural derivation of the two HT forms from the baryte-type BaSO4 structure was identified, with alternating [LaMoO4]+ and [LaSiO4]- layers. The differentiation between these two forms most likely comes from a slightly different arrangement of their respective [LaMoO4] layers. The anisotropic thermal expansion is accompanied by a volume contraction of −0.56% between the two HT forms, and a much larger one (−5.3%) at higher temperatures when the LT form stabilizes.

A Comparative Study on the High-Temperature Forming and Constitutive Modeling of Ti-6Al-4V

A Comparative Study on the High-Temperature Forming and Constitutive Modeling of Ti-6Al-4V