Eutectic Phase Research Articles

Effect of Homogenization Process on Microstructure and Mechanical Properties of 4047 Aluminum Alloy

In this study, the homogenization heat‐treatment process and microstructural evolution of 4047 aluminum alloy are investigated. In the results, it is revealed that the homogenization process induces partial dissolution of metastable phases and modification of the fine needle‐shaped eutectic Si. Within the 4047 aluminum alloy, the fine needle‐shaped eutectic Si undergoes granulation, involving two stages: crystal dissolution and granulation of broken crystals. After optimal homogenization heat treatment, the eutectic Si phase transformed from a fine needle‐shaped structure to small, regular spherical structures, reducing stress concentration and improving the interfacial bonding capability and internal structure of the alloy matrix. This significantly reduces the likelihood of microcrack formation within the alloy and effectively hinders crack propagation, enhancing the alloy's mechanical properties.

Microstructure evolution of a novel Al-8Si-0.4Mg-0.2Sc-0.2Er alloy solidified under permanent magnet stirring

An experimental study has been conducted to assess the influence of permanent magnet stirring (PMS) at various rotation speeds (ω = 40, 80, 120, and 160 rpm) on the solidification microstructure of a novel Al-8Si-0.4Mg-0.2Sc-0.2Er alloy. The results reveal that the Sc and Er would produce small size Al(Sc,Er)2Si2 precipitates in the front of the Si phase under the increased rotation speed of PMS. Furthermore, it has been observed that PMS generates forced fluid flow with the magnetic Taylor number as large as 9.80 × 108, which significantly reduces the size of Al(Sc,Er)2Si2 and eutectic Si phase, promotes the formation of equiaxed dendrite α-Al grains.

Optimizing the mechanical performance of A356–Sc–Sr alloy via combining machine learning and mechanical stirring under vacuum

In this study, a machine learning design system (MLDS) with a property-oriented optimization strategy was first established to predict the mechanical properties of the A356 alloys with adding Sc and Sr elements. Based on the experimental verification from the MLDS, the addition of 0.2 wt% Sc and 0.067 wt% Sr elements led to the refinement of α-Al grains and eutectic Si phases. Then, the vacuum–stirring was introduced to obtain the semi-solid microstructure of the A356–0.2Sc–0.067Sr alloy. The α-Al grains displayed the spherical morphology and the reduction in pores helped improve the mechanical properties of the alloy. In addition, the effects of stirring time and stirring temperature on the microstructure and mechanical properties of the alloy were investigated. The results demonstrated that the α-Al grains of the alloy were further spheroidized, resulting in the improved mechanical properties. The ultimate tensile strength and elongation of the alloy were 220 MPa and 6.0%, respectively, which were increased by 16.8% and 26.7% in comparison to those of the alloy without vacuum–stirring. The aim of this work is to provide a new method to prepare high-performance A356 alloy through composition design and microstructural control.

Microstructure and mechanical properties of IN738LC superalloy repaired by wide gap activated diffusion brazing method

In the current study, the effect of the weight percentage of filler and additive powder on the microstructural and mechanical properties of the wide gap activated diffusion brazing process was studied. IN738LC base metal powder and AMDRY BRB filler were used as filler metal for IN738LC superalloy brazing. Subsequently, diffusional heat treatment and aging cycle were used to modify the microstructure and mechanical properties in the restoration structure. Optical microscope and scanning electron microscope were used to identify the phases in the braze area and four-point bending tests were performed to evaluate the mechanical properties of the wide gap. For the sample brazed at 1180 °C for 30 min, heat treated at 1120 °C for 4 h, and aged at 850 °C for 24 h, the porosity and eutectic phases in the brazed area and the diffusion-affected zone maintained as low as possible. Thus, it can be referred to as the optimized sample. The samples containing 40 wt% filler had the optimum mechanical properties at ambient temperature and high temperature. Fractography showed that the place of crack initiation was mainly in the filler metal.

Experimental characterization and 3D sharp-interface model simulation of grain refinement during solidification of nano-TiCN/Al–7Si composites

Significant grain refinement was achieved in nano-TiCN/Al-7 wt.% Si composites through growth control induced by nano-TiCN particles (NPs). The microstructures displayed two types of NP distributions: within interdendritic eutectic Si phase and along grain boundaries. This refined microstructure contributed to enhancing mechanical properties. To elucidate the grain refinement mechanism in nano-TiCN/Al–7Si composites, a three-dimensional (3D) sharp interface model (SIM) was developed, integrating the cellular automaton (CA) technique with a transformation matrix comprising three Euler angles. This 3D SIM effectively replicated the dendritic morphology of α-Al. The exact impact of latent heat on grain refinement was clarified. The observed grain refinement induced by NPs could not be numerically reproduced without considering latent heat. The grain refinement in TiCN/Al–7Si composites is governed by multiple factors. As NPs layers inhibits solute diffusion along the solid-liquid interface, the dendrite growth rate reduces, leading to the reduced rate of latent-heat release. Consequently, constitutional undercooling in the surrounding liquid increases, activating more heterogeneous nuclei. The developed SIM model offers deeper insights into the grain refinement mechanism induced by TiCN NPs in Al–7Si alloy.

A sensitive determination of Brilliant Blue FCF in some food samples using hydrophillic deep eutectic solvent-assisted magnetic nano gel-based dispersive solid phase microextraction prior to spectrophotometric analysis

A new magnetic nano gel (MNG) was prepared from choline chloride/phenol deep eutectic solvent and magnetic amberlite XAD-7 nanocomposite. The dispersive solid phase micro extraction (dSPME) method was developed for seperation and preconcentration of Brilliant Blue FCF (BB) by the prepared MNG. In this study, firstly, the optimum DES type and mole ratio of DES were investigated before response surface methodology optimization. Then, the effect of the MNG-dSPME experimental parameters were optimized by response surface methodology using central composite design. Under the optimum microextraction conditions, limit of detection (LOD), limit of quantification (LOQ), preconcentration factor (PF), enhencament factor (EF) were found to be 1.15 μg L−1,3.80 µg L-1, 70, and 88, respectively. It was seen that the recovery of real samples were obtained from 95.5 to 103.6%. The pesent method was succesfully for extraction of BB in some food, personal care samples, to the best of our knowledge, this is the first study that is presented method on determination of BB by preconcentration with magnetic nano gel. The obtained results showed that the present procedure is effective, sensitive, and has high accuracy for the quantitative detection of BB.

Simultaneous improvement of mechanical and castability properties of Al-Cu-Mn based alloys by Ca/Ni micro-alloying

Currently one major barrier for the design of cast high-strength and high-toughness Al alloys is hot tearing. In this work, a strategy of combination of squeeze casting and microalloying (Ca/Ni eutectic elements) in Al-Cu-Mn based alloys was employed to inherit the excellent mechanical properties of Al-Cu alloys whilst simultaneously reducing their tendency to hot tearing. The developed alloys exhibit comparable castability (fluidity and hot tear resistance) to A356, which is widely available commercially. However, their comprehensive mechanical properties far exceed those of A356. Trace Ca/Ni additions markedly reduce the grain size of the alloy and simultaneously increase the fraction of intergranular low melting point eutectic liquid phases, which is beneficial to the improvement of liquid feeding. The fine equiaxed grains have excellent thermal shrinkage coordination, while the high volume fraction eutectic liquid phase delays the development of grain cohesive skeleton. Accordingly, the localized shrinkage stress/strain at the hot spot is released timely, thus inhibiting the emergence and propagation of hot cracks in the brittle solidification interval. The diminished hot tearing susceptibility is attributed to the reduced load onset temperature and load values in the hot spot region. A new intergranular bridging mechanism is discovered in low-Ca alloys: based on compositional segregation-induced nucleation of an intergranular bridging skeleton, which strengthens the intergranular adhesive force and effectively reduces the hot tearing tendency of the alloys. The alloys with high-Ca/Ni additions, however, reduce the hot tearing tendency by healing cracks through eutectic liquid phase backfill. The results of the hot tearing experiments of the developed alloys are analyzed with the current hot tearing evaluation criteria. The results demonstrate that the predictions of the Kou's criterion provide guidelines for the design of alloys that are resistant to hot tearing.

Corrosion behaviour of SiC particulate reinforced AZ31 magnesium matrix composite in 3.5 % NaCl with and without heat treatment

Magnesium is a lightweight structural material widely utilised in automotive applications. To enhance its mechanical properties, ceramic particulate reinforcement can be incorporated, particularly for wear resistance and high-temperature applications. However, the addition of ceramic particles to magnesium can compromise its corrosion resistance due to microgalvanic cell formation at the interfaces between the Mg matrix and the second phase. This reduces the chemical protection provided by the passive film. In this study, the corrosion properties of AZ31 and AZ31-5SiC samples were investigated, with a focus on the effect of heat treatment. Detailed microstructural and electrochemical analyses revealed that the AZ31 cast sample forms an effective passive film, resulting in improved corrosion resistance. However, the addition of SiC particles to AZ31 increased the corrosion rate, with corrosion mechanisms evolving over time. To mitigate these effects, a heat treatment process was employed to dissolve β-Mg17Al12 eutectic and Al8Mn5 intermetallic phases. The heat-treated AZ31 with SiC exhibited an improvement in corrosion resistance. These findings highlight the potential for heat treatment to enhance their corrosion resistance, thereby broadening their application prospects.

Development and preparation of novel nano-enhanced organic eutectic phase change materials for low-temperature solar thermal applications

ABSTRACT Thermally reliable and stable eco-friendly Phase change materials are of significant aid in thermal energy storage technology, leading to improved energy utilization and reliability of the system. This study develops two novel organic eutectic PCM of Lauric acid – Margaric acid (LM) and Myristic acid – Margaric acid (MM), which are chemically stable and thermally compatible for latent heat energy storage. LM eutectic mixture had a melting temperature of 52.66°C with a latent heat of 163.68 J/g, and MM eutectic mixture had its melting temperature at 44.79°C and a latent heat of 197.31 J/g. The phase change temperatures were favorable for low temperature solar thermal applications with good latent heat capacity. The thermal characteristics of these eutectic mixtures are further enhanced with the dispersion of highly conductive Multi walled carbon nanotubes (MWCNT) at three different mass fractions (.5%, 1% and 1.5% by weight). Nano enhancement could achieve exceptional thermal conductivity enhancement in MM eutectic mixture by 110.6% and 83.73% in LM eutectic mixture. Thermogravimetric analysis and Fourier-transform infrared spectroscopy analysis ensured the thermal and chemical stability of the eutectic mixtures. The optical absorption characteristics were extensively enhanced with nano particle addition, which is highly preferable in solar thermal applications.

Microstructure Evolution and Homogenization Kinetics of 15Cr–30Ni–Fe Heat‐Resistant Alloy

The as‐cast microstructure, microsegregation of alloying elements, and microstructure evolution during homogenization of the newly designed 15Cr–30Ni–Fe heat‐resistant alloy are studied. Ti, Nb, Si, and Mo segregate at the interdendritic region. The brittle eutectic Laves phase contains Fe, Ti, Ni, Nb, Si, and Mo, which is identified as the Fe2Ti Laves phase. The activation energy for the Fe2Ti Laves phase dissolution is close to the activation energy for Ti diffusion in the γ matrix based on the Johnson–Mehl–Avrami–Kolmogorov analysis. The back‐diffusion of Ti to the γ matrix is the limiting step for the dissolution of Fe2Ti Laves phase. The kinetic equation of homogenization considering lattice parameters and pre‐exponential factor correction is established. After the double‐stage homogenization at 980 °C/10 h + 1140 °C/4 h, the volume fraction of the Laves phase decreases from 5.11% to 0.26%, and the large eutectic Laves phase is completely dissolved. The reduction in the standard deviation of microhardness at different soaking times effectively reflects the gradual decrease in the degree of microsegregation of alloying elements. The average grain size of the alloy after homogenization is 410 ± 63.1 μm, which is beneficial to control the further refinement of grain during the subsequent hot working.

Decoupling effect stimulated independent dendrite growth of eutectic phases under microgravity and containerless states

Eutectic growth process is usually characterized by the simultaneous coupled growth of two different solids within one uniform liquid phase, while fluid dynamics normally predicts the equiaxed shrinkage for floating viscous droplets on freezing. Here a decoupling effect was induced by the microgravity and containerless states aboard space station, which led to the independent dendrite growth of two eutectic phases within extremely undercooled liquid Nb-Si refractory alloy. The confronting fluid flow pattern driven by polar heterogeneous nucleation was found to stimulate the elongated surface deformation of alloy droplet at a high dendrite growth velocity.

Development of NiCrFeCoBX eutectic high entropy alloy coating by laser cladding: Investigation of microstructural, solidification, corrosion, and wear properties

Developing protective coatings resistant to corrosion and wear has always been a challenge in various industries. In this work, we processed NiCrFeCoBx (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) high-entropy alloy by laser cladding on a GTD-111 superalloy. At B ≤ 0.3, the microstructure of the coating consisting of inter-dendritic FCC1 and FCC2 lamellae coupling was confirmed by XRD and SEM analysis. By increasing the value of B (B≥ 0.4), a coating with the phase structures of FCC1, FCC2, and MXBY was identified. The presence of Cr-rich borides (MXBY) was attributed to the enrichment of the eutectic composition with B and its segregation into interdendritic regions. With increasing B, more areas were created for inhomogeneous nucleation of dendrites from the melt, resulting in a finer eutectic structure with a higher volume fraction. The comparison between B0.1 and B0.6 samples showed that the hardness increased from 240 HV to 603 HV and the coefficient of friction decreased from 0.63 to 0.42. Raising the B value led to a drop in the corrosion current potential of the NiCrFeCoBX coating from −0.456 V to −0.895 V in a 3.5 % NaCl solution. Additionally, this shift altered the corrosion mechanism from pitting to intergranular corrosion. This was attributed to the high surface energy of the eutectic phase and the intensification of galvanic corrosion.

Preparation and investigation of green and cheap deep eutectic solvents for determination of essential and toxic metal ions at trace levels in different coffee products

In this research, a vortex-assisted hydrophobic deep eutectic solvent-based dispersive liquid phase microextraction (VA-HDES-DLPME) method was developed to extract some essential (Fe, Mn and Zn) and toxic (Cd and Pb) metal ions from coffee products. After the VA-HDES-DLPME method, the amounts of the metal ions in the HDES-phase were determined by flame atomic absorption spectrophotometry (FAAS). For selective extraction of metal ions, five HDESs (as extraction solvent) were prepared and tested according to the ultrasonic-assisted procedure. Some dispersive solvents were investigated to ensure the dispersion of HDES in the sample solution. In the VA-HDES-DLPME method, heating and centrifugation steps were not required to separate the HDES-phase from the sample solution. Key factors were investigated and optimized to achieve selective and rapid extraction of metal ions. Under optimized conditions, the working range of the VA-HDES-DLPME method for metal ions ranged from 0.03 to 280 μg kg−1. The detection limits of Fe(II), Mn(II), Zn(II), Cd(II), and Pb(II) ions were 0.01, 0.27, 0.02, 0.015, and 0.18 μg kg−1, respectively. Relative standard deviation and extraction recovery for five replicate runs of 5 μg kg−1 of metal ions were in the range of 1.3%–1.9% and 94 ± 4%-98 ± 2%, respectively. Validation of the VA-HDES-DLPME method was tested by studies on three reference materials. In the final step, the VA-HDES-DLPME method was successfully applied to microwave digestion of coffee samples using a standard addition method. The obtained quantitative recoveries showed the good accuracy of the method.

The use of deep eutectic solvent-liquid phase microextraction as green analytical sample treatment for the analysis of drugs in urine

In this paper, a natural deep eutectic solvent (NADES)-based liquid phase microextraction (LPME) of 20 pharmaceuticals from urine, employing liquid chromatography tandem mass spectrometry (LC-MS/MS) for precise quantification, has been developed. The chromatographic gradient was accurately evaluated to ensure the effective separation of tramadol, an opioid receptor agonist, and o-desmethylvenlafaxine, one active metabolite of the antidepressant venlafaxine, both compounds sharing identical molecular mass for the precursor ion (Q1: 264.2 m/z) and fragmentation patterns (Quantifier ion: 58.2 m/z; qualifier ion: 246.0 m/z). NADES consisted of menthol-octanoic acid in a molar ratio of 1:2. Using the appropriate extraction conditions, the developed methodology provided appropriate LOQ values, ranging from 15 to 208 ng L–1, with reasonable RSD values (below 11 %), recoveries ranging from 64 to 120 % and preconcentration factors up to 66.6 folds. Application of the developed method to the analysis of urine samples served to highlight its usefulness. An AGREEprep score of 0.64 was obtained despite the demand for substantial sample volumes and the use of LC-MS/MS for analyte determination.

Eutectic phase change composites with MXene nanoparticles for enhanced photothermal absorption and conversion capacity

Phase change composite materials with uniform nanomaterial dispersion are potential solutions for improving thermophysical properties and enhancing latent heat capacity applicable in thermal management. In this study, various transitional carbide-based MXene samples were synthesised via acid etching to augment the heat transfer capacity and efficiency of the solar thermal energy storage (TES). These samples were then uniformly dispersed in a eutectic mixture (1:1) of paraffin wax (PW) and polyethylene glycol (PEG-6000), resulting in the formation of a MePCM composite. The controllable porous structure and hydrogen interactions with the external layer of MXene and long-chain PCM benefitted in the well impregnation of PCM and compatibility impregnated into the composite. An exceptionally higher mass fraction of 1 wt % Ti3C2Tx MXene-based phase change composite unveiled a higher phase change enthalpy of 138.66 J/g in the melting phase and 139.54 J/g in the solidification phase with 89.82 % energy storage efficiency. In contrast to pure eutectic PCM (0.2593 W/mK), the thermal conductivity of MePCM composite is relatively higher and provides a thermal conductivity of 0.9209 W/mK for Ti3C2Tx MXene-based composite. The enhancement of thermal conductivity is ascribed to the increased heat conduction pathway facilitated by the MXene arrangement. The utilisation of spatially constrained eutectic phase change material (PCM) assembly resulted in the development of MePCM, which exhibited enhanced thermal conductivity, chemical and physical stability, and thermal consistency across 500 melting-solidification cycles. Benefitting from the thermal conduction path, the MePCM exhibits an excellent photothermal conversion efficiency of 98.53 %. The thermal responsive tests of Ti3C2Tx and V2CTx MXene composite samples provide better thermal response than eutectic PCM without thermal reduction. With a higher thermal storage capacity and higher heat transfer property, thermally reliable MePCM composites exhibited tremendous potential for photothermal applications.

Microstructure evolution and corrosion behavior of TIG welded joint of a new Mg[sbnd]Gd[sbnd]Nd[sbnd]Zn[sbnd]Zr alloy during post-weld heat treatment

The corrosion behavior of the tungsten inert gas (TIG) welded Mg3Nd3Gd0.2Zn0.5Zr alloy with different post-weld heat treatments was systematically investigated. The results show that the corrosion resistance of the sand-cast base material (BM) was inferior to that of the fusion zone (FZ), which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg3(Nd, Gd) eutectic phases and numerous β precipitates. It is found that post-weld solid-solution (T4) treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution. The precipitation of nanosized phases and ZnZr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged (T6) joint. As the main corrosion products, MgO and Mg(OH)2 are distributed throughout the whole corrosion film, while RE oxides and RE hydroxides are mainly distributed in the inner layer, which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)2. Based on the composition and structure of the corrosion product film, a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints. This work could promote the applications of welded MgRE alloy joint in some corrosion environments.

Influence of cooling speeds on the microstructure and properties of A356 aluminum alloy after squeeze casting

The examination focuses on the microstructural characteristics and mechanical attributes of A356 alloy subsequent to squeeze casting performed under varying cooling speeds. The findings reveal that the cooling speeds have no notable impact on the size of the grains in the A356 alloy produced through squeeze casting. However, as the cooling speeds increase, the eutectic Si phase in A356 alloy decreases, transforming it from coarse flakes to small rods or particles, thereby enhancing the mechanical characteristics of the alloy. The water-cooled alloy has the best UTS performance, whose value of A356 alloy after squeeze casting is 287 MPa.

Effect of Ni and Sr on the microstructure and tensile properties of the squeeze cast Al‐Si‐Cu alloy at elevated temperatures

AbstractThe influence of the transition alloying element nickel and the alkaline earth element strontium on the microstructure and tensile properties of squeeze cast Al−Si‐Cu alloy under as‐cast condition at elevated temperature of 100 °C, 200 °C and 300 °C is investigated in comparison with the conventional Al−Si‐Cu alloy (A380). Aluminum alloy A380 is alloyed and modified with 2 wt% additional nickel (Ni) and 0.02 wt% strontium (Sr). Squeeze casting is employed to cast the modified A380 under an applied pressure of 90 MPa. The results of tensile testing at the selected elevated temperatures indicate that the Ni and Sr containing A380 alloy exhibits a significantly improvement on tensile properties, specifically ultimate tensile strength and yield strength with 10 %‐30 % increases. The as‐cast microstructures of both the conventional and Ni and Sr‐containing alloys are observed by an optical microscope and further analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of Ni‐containing intermetallic phases with Ni addition, and the modified eutectic Si phase with refined morphologies due to the Sr addition should be responsible for the considerable enhancement on the as‐cast strengths of the squeeze cast Ni‐ and Sr‐containing alloy over those of the conventional A380 alloy.

A novel high-strength Al–Li alloy printed by laser powder bed fusion: Microstructural evolution and strengthenin mechanism

This paper obtained an additively manufactured high-strength Al–Li alloy by laser powder bed fusion (LPBF) based on a third generation AA2195 alloy powder raw material. The relationship between the process optimization, microstructure evolution, and mechanical properties of the as-printed (AP) and heat-treated (HT) specimens was established for the first time to explain the intergranular fracture sensibility during LPBF and reveal the dominant precipitation strengthening mechanism induced by the subsequent heat treatment. The precipitation order of AP Al–Li alloy at the last stage of the solidification process was: L (Liquid phase) →T2 (Al6CuLi3) + θ′(Al2Cu) + δ′/β' (Al3(Li,Zr)) + T (LiAlSi) + Ω (AlCuMgAg). The micro-cracks caused by a relatively high grain boundary coverage of interconnected film-like eutectic phases, as well as micro-voids caused by the localized slip between the coarse T2-phases and soft precipitate-free zones, resulted in the high intergranular fracture sensibility. The well-designed T6 heat treatment of 515 °C/60 min solution treatment and 170 °C/6 h aging treatment was conducted to maximize the precipitation strengthening by T1-phases. The precipitation order of HT Al–Li alloy was supersaturated solid solution → GP zone + δ′/β' → θ′ + T1 (Al2CuLi) + ω (Al7Cu2Fe) + β′. The presence of continuously distributed T1-cells along the grain boundaries was not only capable of providing a pinning effect on dislocations movement and boundary migration, but also able to shorten the pile-up distance on the slip plane. Such phenomena improved the resistance ability of Al–Li alloys to mechanical damage and permitted a significant strength enhancement.

The Effect of Sulfuric Acid Anodization on the Electrochemical Properties of Aluminum Alloy AlSi10Mg Prepared by Selective Laser Melting

Aluminum alloy, AlSi10Mg, prepared by selective laser melt (SLM) fabrication was anodized in 9.8% sulfuric acid (Type II) at 15 V for a total of 23 min. Experiments were performed to study the potentiostatic anodization process and its effects on the oxide coating morphology, thickness, and electrochemical properties of the alloy. Prior to anodization, the alloy microstructure is composed of aluminum cells encapsulated in a silicon network. Anodizing the abraded and polished AlSi10Mg surface produced a porous oxide layer with a thickness of 5 μm. The oxide coating weight was 698 ± 29 mg/ft2. The oxide coating forms in the aluminum cells that are isolated from one another by the silicon eutectic phase. In electrochemical tests, the anodic and cathodic potentiodynamic polarization currents were suppressed by factors of 15× and 215×, respectively, as compared to the unanodized controls. The data indicate the anodic oxide coating suppresses the cathodic more than the anodic reaction rate. Linear polarization resistance (R p) values increased by 279× after anodization. The corrosion current density values (j corr) decreased by 133× after anodization. Taken together, the electrochemical data indicate the anodic oxide coating (unsealed) increases the corrosion resistance of the SLM alloy by two orders of magnitude.