Beta Phase Research Articles

Identification and Quantitative Analysis of the Isolated and Adhesive Beta Phases in Titanium Alloy Ti–6Al–4V

Identification and Quantitative Analysis of the Isolated and Adhesive Beta Phases in Titanium Alloy Ti–6Al–4V

Analysis of crystallographic orientation and morphology of microstructure during hot working for an alpha/beta titanium alloy

This work focuses on analysis of microstructure morphology and crystallographic orientation for Ti-17 alloy during hot working. The results show that alpha phase and beta phase influence each other and there is a coordinate deformation between them. The non-uniform deformation is observed under small deformation conditions. The observing area can be divided into small deformation zone (area L) and large deformation zone (area H). Both alpha and beta phases remain the initial morphology, and they have better capability of coordinate deformation in area L, while coordinate capability is weak in area H in which alpha phase is globularized. Correspondingly, the Burgers orientation relations are well preserved in area L, but the orientation relations are more or less destroyed in area H. Dynamic recovery is the main mechanism of beta phase evolution when height reduction is lower. By contrast, the continuous dynamic recrystallization (CDRX) of beta phase gradually dominates the deformation pattern as the deformation increases. An uniformly globularized alpha structure is obtained under large deformation condition. The unsynchronized rotation of alpha phase around <11−20> pole occurs during deformation, which leads to the uniform crystal structure inside the same alpha lamellae. This process is an important step of globularization of the lamellar structure.

Hydrothermal synthesis of alkali-free chabazite zeolites

Alkali-free siliceous CHA zeolites with a wide Si/Al ratio ranging from 11 to infinity have been synthesized in hydroxide and fluoride media using either N,N,N-Trimethyl-1-adamantammonium (TMAda), N,N,N-Dimethylethylcyclohexyl ammonium (DMECHA) cations, or a mixture thereof. TMAda, in combination with other low-cost organic templates, allowed the formation of pure silica CHA without any impurities in the synthesis gel with an H2O/SiO2 ratio of 3. Single-phase crystalline pure silica CHA was produced by DMECHA within a very narrow range of H2O/SiO2 ratio, and small deviations in the water content from this range led to the formation of a slightly less dense zeolite beta phase. Alkali-free siliceous CHA zeolites possessing a high crystallinity and a variety of particle sizes were successfully prepared for the first time using a low-cost DMECHA template, particularly by a direct interzeolite transformation of FAU zeolites having the same secondary building unit of double-6-rings (D6Rs). This makes DMECHA an attractive organic structure-directing agent (OSDA) for wide applications of CHA zeolites as catalysts and adsorbents.

Ni(OH)2 as an novel shell layer material for core-shell dielectric filler based on barium titanate and their dielectric polymer composites in P(VDF-HFP) matrix

Dielectric capacitors with high dielectric constant and energy density are of great importance for electronic devices. Barium titanate(BaTiO3) have been widely explored for polymer-based dielectric composites owning to its ultrahigh dielectric constant and commercial availability. However, due to the large difference of dielectric constant between BaTiO3 and polymer matrix, the interface becomes fragile under electric field, which is not conducive for the improvement in breakdown strength and energy storage density. Herein, a flower like barium titanate/nickel hydroxide(BTO/Ni(OH)2) core-shell structured filler has been fabricated to provide a novel approach to modify the interface between BTO and P(VDF-HFP) matrix for dielectric polymer composites. Ni(OH)2 nanoflakes have grown in-situ on the surface of hydroxylated BaTiO3 particles to form the flower like core-shell assemblies via hydrothermal reaction. Then, these synthetic BTO/Ni(OH)2 particles with specific flower-like core-shell structure can be uniformly dispersed in P(VDF-HFP) without any additional surface modification due to their surface –OH groups. Meanwhile, Ni(OH)2 shell triggered beta phase of P(VDF-HFP) near core-shell filler based on the interfacial interaction between Ni(OH)2 and P(VDF-HFP). Thus, the intensity of the local electric field can be gradually reduced due to the formation of a dielectric constant gradient. Besides, these Ni(OH)2 nanoflakes shell are able to cut down the local electric field and prevent the growth of electrical trees on the surface of BaTiO3 during breakdown process. When the composite filler content is 10 wt%, the dielectric constant and breakdown strength increases to 14.8 and 330 kV/mm from 11 to 260 kV/mm, respectively. And the calculated energy density is 7.13 J/cm3, which is 1.5 times that of 10 wt% BTO/P(VDF-HFP) composite film. This study provides a novel shell material Ni(OH)2 for the preparation of BTO core-shell structure filler, which has good compatibility with polymer substrates.

Structural Tailing and Pyroelectric Energy Harvesting of P(VDF-TrFE) and P(VDF-TrFE-CTFE) Ferroelectric Polymer Blends.

The copolymer P(VDF-TrFE) is a normal ferroelectric because the bulky TrFE monomer improves its crystalline chain structure, while the terpolymer P(VDF-TrFE-CTFE) is a relaxor ferroelectric because the third monomer CTFE makes it amorphous. Herein, in order to induce a crystalline beta phase in the terpolymer, we blended a small amount of crystalline P(VDF-TrFE) into P(VDF-TrFE-CTFE) and investigated the effect of blending on the pyroelectric energy harvesting (PyEH) properties. The polarization-electric field hysteresis loops at different temperatures and energy densities were investigated. The PyEH energy density (ND) is compared with the electrical energy density (UE). The UE and ND at the ferroelectric–paraelectric transition temperature for the χ = 0.1 blend are reported as 3.18 and 5.04 J/cm3, respectively, which are higher than the other polymer blends. Interestingly, the ND of the χ = 0.9 blend is found to be 3.44 J/cm3 when operated at lower and higher temperatures, that is, at TL = 25 °C and TH = 40 °C, respectively, which is the highest possible energy density at the lowest possible transition temperature for the polymer blends.

A Robust Algorithm to Calculate Parent Β Grain Shapes and Orientations from α Phase Electron Backscatter Diffraction Data in α/β -Titanium Alloys

This paper presents a new model and open-source algorithm for reconstructing prior beta phase orientation and grain shapes from measured alpha-phase electron backscatter diffraction data in α/β titanium alloys. It is based on the image segmentation model of Mumford and Shah, which includes a regularization term that helps create smooth boundaries and overcomes short comings of prior reconstruction techniques. Additionally, the new algorithm is resilient to noise. Our algorithm's effectiveness is demonstrated on simulated and real world data.

Ultrafine-Grained Two-Phase High-Entropy Alloy Microstructures Obtained via Recrystallization: Mechanical Properties

A metallurgical methodology has been set up to design alloys with improved mechanical properties such as strength-ductility synergy, via improved strain hardening. To this end, a multi-concepts approach including High-Entropy-Alloys (HEA), grain refinement, chemical contrast and using the transformation induced plasticity (TRIP) deformation mechanism has been implemented. The use of a conventional thermomechanical treatment comprising cold rolling followed by annealing at 650°C, produced two high entropy alloys with submicron alpha (hcp) and beta (bcc) phases. For Ti35-5-5 alloys, stress-induced martensitic transformation, and its subsequent reverse transformation during annealing at 650°C, led to a well-recrystallized state. A microstructure consisting of alpha and beta equiaxed grains was obtained, whose size increased within the submicron domain from about 300 nm to 600 nm with the holding time between 15 to 300 min. Contrariwise, for Ti35-6.5-6.5, which does not deform by the TRIP effect, the same thermomechanical treatment does not produce the recrystallization. Rather precipitation of platelets in the recovered beta matrix occurred. As for the mechanical properties, the yield strengths of the alloys with dual-phase microstructure lie between 950 and 1150 MPa for Ti35-5-5 and between 850 and 950 for Ti35-6.5-6.5 counterpart, for annealing times ranging from 15 min (higher yield strength) to 300 min (lower yield strength). This corresponds to a very large increase in the yield strength compared to that of the as-cast alloys, displaying values of about 400 MPa and 725 MPa for Ti35-5-5 and Ti35-6.5-6.5, respectively. Reasonable ductility was obtained for the alloys with optimized microstructures, that both display a tensile ductility of about 12% after annealing for 300 min at 650°C

Simple deposition of mixed α, β-nickel hydroxide thin film onto nickel foam as high-performance supercapacitor electrode material

Here, uniform thin nanosheets’ film of mixed α- and β-Ni(OH)2 phases was cathodically electrodeposited onto nickel foam support and the fabricated electrode was utilized as binder-free electrode for supercapacitor applications. An additive-free aqueous electrolyte of 0.05 M nickel nitrate was used as the deposition bath, where the hydroxide film was prepared with only applying direct current of 10 mA/cm2 in a two-electrode system while a uniform electrical field was established through using two counter electrodes parallel to nickel foam cathode. The morphology, crystalline phase and also specific surface area of the deposited nickel hydroxide film onto Ni foam were analyzed using field-emission scanning electron (FE-SEM) and X-ray diffraction (XRD) techniques as well as BET and FT-IR spectroscopy. These analyses proved that a mixed alpha and beta phases of Ni(OH)2 with uniform nanosheets’ morphology are grown onto the nickel foam cathode. The electrochemical investigations using CV, GCD and electrochemical impedance spectroscopy (EIS) manifested the designed electrode provides specific capacitance of 2143 F g−1 at a current density of 0.5 A g−1 with high rate capability of 65% by increasing the current density from 0.5 to 20 A g−1 as well as 90% and 74% cycling stability at the current densities of 5 and 15 A/g, respectively. The excellent electrochemical performance of the as-prepared electrode is ascribed to the simultaneous deposition of both α and β phases through using a facile electrochemical deposition method. The presence of α and β phases guarantees the high specific capacitance and high cycling stability of the prepared electrode, respectively.

Different behavior of alpha and beta phases in a Low Stacking Fault Energy copper alloy under severe plastic deformation

In this research, two phase brass alloy as one of the most important copper base alloys was processed by equal channel angular pressing as a severe plastic deformation process. The process was performed at 350 °C in route C up to 6 passes. Microstructural study showed that discontinuous recrystallization initiated at the first pass in the alpha phase. Recrystallization fraction enhanced by increasing the amount of strain and grain size decreased to less than one micron after the fifth and sixth passes. Investigations of beta phase showed that recrystallization in this phase began after the third pass and enhanced with increasing the number of passes. Separate investigation of macro-texture for two phases of alpha and beta well proved the different deformation behavior in both phases. Furthermore, it was observed that Goss, Rotated Goss and Rotated cube texture components were dominant for alpha phase, and cube and {112} <111> texture components were dominant for beta phase that had a direct impact on the results of mechanical properties. Micro-hardness and tensile test were used in order to study the mechanical properties of the alloy. The results indicated a massive increase in micro-hardness and tensile strength after the process. Also, total elongation in the processed specimens was higher than expectations in a manner that after the final pass, it reached more than 80% which was only approximately 35% less than the primary anneal specimen.

Beyond physical entrainment: competitive and cooperative mental stances during identical joint-action tasks differently affect inter-subjective neural synchrony and judgments of agency

ABSTRACT Little work has examined how mental stance alone, apart from physical entrainment, affects between-participant neural synchrony during joint social interaction. We report the first findings on how cooperative and competitive mental stances, even during identical visuomotor joint-action tasks, result in distinct neural oscillatory signatures in low beta and theta band between-participant phase synchrony. Two participants jointly controlled a cursor and were instructed to either compete or cooperate to move it to one of three targets. The visuomotor output was identical for both the compete and cooperate conditions because participants were privately given the same target for experimental trials. Cooperation enhanced theta band between-participant phase-locking value (PLV) midtrial at 1-2 seconds, reflecting activation of systems for social coordination to move the cursor in a shared direction. Competition enhanced low beta between-participant PLV, shifting from temporal to frontal regions, indicating that participants focused only on their target and later evaluated self-agency as winner or loser. This interpretation of the neural signature was corroborated by participants’ greater post-trial ratings of the degree of control over the cursor during competition. Top-down cooperative and competitive mental stances shape perceptions of social context and affect interpersonal neural synchrony important for representation of self and others’ actions.

Market Power and Asymmetric Learning in Product Markets

We study how market structures and asymmetries in learning technologies affect trade in a product market. In this market, a new product of unknown quality is introduced to challenge a pre-existing product of known quality. We show that market efficiency (the first-best) is achieved both under monopoly and competition if buyers are symmetric in their learning process. Instead, if buyers are asymmetric, only a monopolistic market in which the seller of the old product also sells the new one is efficient. We identify inefficiency as a learning externality that consumption of the unknown quality product by one buyer generates for the other buyers. The equilibrium inefficiency has two essential features: (i) Efficiency at the top: the threshold for starting to serve the best learners (i.e., to enter into a Beta phase) remains the optimal one; (ii) Non-monotonicity: distortions are not monotone in the extent of the asymmetry. Importantly, if sellers can offer take-it-or-leave-it multilateral contracts, the distortion disappears. Finally, we explore our results’ robustness under different assumptions about the ability to price discriminate and other market structures.

Microstructure and Mechanical Properties of Titanium–Equine Bone Biocomposites

Microstructure and mechanical properties of Ti-6Al-4V/equine bone (EB) composites fabricated by ball milling and spark plasma sintering (SPS) have been investigated. Ti-6Al-4V/EB composites were successfully fabricated by a planetary ball-milling of spherical Ti6Al4V powder and natural EB powder and SPS at 1000 °C within 15 min under 50 MPa. EB was uniformly dispersed in the Ti6Al4V matrix owing to ball-milling, and beta phase transformation temperature of 1000 °C provided phase stability. The composites containing 0.5 wt.% EB exhibit Vickers hardness and elastic modulus of 540.6 HV and 130.5 GPa, respectively. The microstructures and mechanical properties of the composites were observed using scanning electron micrograph and nanoindentation.

A process-microstructure finite element simulation framework for predicting phase transformations and microhardness for directed energy deposition of Ti6Al4V

This paper presents a process-microstructure finite element modeling framework for predicting the evolution of volumetric phase fractions and microhardness during laser directed energy deposition (DED) additive manufacturing of Ti6Al4V. Based on recent experimental observations, the present microstructure evolution model is formulated to combine the formation and dissolution kinetics of grain boundary, Widmanstätten colony/basketweave, massive/martensitic alpha and beta phases of Ti6Al4V. The microstructure evolution algorithm is verified and embedded into a three-dimensional finite element process simulation model to simulate thermally driven phase transformations during DED processing of a Ti6Al4V thin-walled rectangular sample. The microhardness values of different locations of the part, which experience different thermal histories, are computed based on the simulated fractions and hardness values of different phases in the final microstructure. The simulated volumetric phase fractions and related microhardness distribution agree reasonably well with experimental measurements performed on the sample. Thus the proposed simulation model could be useful for designers to understand and control process-microstructure-property relationships in a DED-processed part.

Impact of Laser Structuring on Medical-Grade Titanium: Surface Characterization and In Vitro Evaluation of Osteoblast Attachment.

Improved implant osteointegration offers meaningful potential for orthopedic, spinal, and dental implants. In this study, a laser treatment was used for the structuring of a titanium alloy (Ti6Al4V) surface combined with a titanium dioxide coating, whereby a porous surface was created. The objective was to characterize the pore structure shape, treatment-related metallographic changes, cytocompatibility, and attachment of osteoblast-like cells (MG-63). The treatment generated specific bottleneck pore shapes, offering the potential for the interlocking of osteoblasts within undercuts in the implant surface. The pore dimensions were a bottleneck diameter of 27 µm (SD: 4 µm), an inner pore width of 78 µm (SD: 6 µm), and a pore depth of 129 µm (SD: 8 µm). The introduced energy of the laser changed the metallic structure of the alloy within the heat-affected region (approximately 66 µm) without any indication of a micro cracking formation. The phase of the alloy (microcrystalline alpha + beta) was changed to a martensite alpha phase in the surface region and an alpha + beta phase in the transition region between the pores. The MG-63 cells adhered to the structured titanium surface within 30 min and grew with numerous filopodia over and into the pores over the following days. Cell viability was improved on the structured surface compared to pure titanium, indicating good cytocompatibility. In particular, the demonstrated affinity of MG-63 cells to grow into the pores offers the potential to provide significantly improved implant fixation in further in vivo studies.

Microstructural examination and corrosion behavior of selective laser melted and conventionally manufactured Ti6Al4V for dental applications

The selective laser melting of Ti6Al4V would induce definite changes in the microstructure that may affect its corrosion properties. Microstructural examination showed the formation of relatively thin beta (β) lamella in selective laser melted (SLM) Ti6Al4V compared to wrought Ti6Al4V. X-ray diffraction analysis (XRD) analysis confirmed the presence of alpha and beta phases in both SLM and wrought Ti6Al4V. However, the higher concentration of the β phase in SLM Ti6Al4V compared to wrought Ti6Al4V was evident in the microstructure. As candidate dental implant materials, the corrosion behavior of both SLM and wrought Ti6Al4V was assessed in artificial saliva (AS) and deionized water (DI) containing various species i.e. fluoride (F), calcium chloride (CaCl2) and lactic acid (LA). Electrochemical impedance spectroscopy and potentiodynamic polarization analysis was carried out to estimate the corrosion behavior of SLM and wrought Ti6Al4V at room temperature. SLM Ti6Al4V offered better corrosion resistance than wrought Ti6Al4V in all solutions at pH>6. However, wrought Ti6Al4V comparatively presented high corrosion resistance in AS + LA, DI+CaCl2 and DI+LA solutions (pH<6). The lower dissolution rate of SLM Ti6Al4V (at pH>6) was attributed to larger β content in the microstructure compared to wrought Ti6Al4V.

Development of novel Ti-Mo-Mn alloys for biomedical applications

Due to excellent biocompatibility and corrosion resistance, the application of titanium alloys in orthopedic and dental implants has been increasing since the 1970s. However, the elasticity of these alloys as measured by their Young’s modulus is still about two to four times higher than that of human cortical bone. The most widely used titanium alloy for biomedical applications is Ti-6Al-4V, however, previous studies have shown that the vanadium used in this alloy causes allergic reactions in human tissue and aluminum, also used in the alloy, has been associated with neurological disorders. To solve this problem, new titanium alloys without the presence of these elements and with the addition of different elements, usually beta-stabilizers, are being developed. Manganese is a strong candidate as an alloying element for the development of new beta-type titanium alloys, due to its abundance and low cytotoxicity. In this study, Ti-10Mo-5Mn, Ti-15Mo-2.5Mn and Ti-15Mo-5Mn alloys were prepared in an arc furnace, which resulted in an alloy structure clearly showing the predominance of the beta phase with a body-centered cubic crystalline structure. The observed microstructure confirmed the results on the structural characterization of alloys. Measurement of the indirect cytotoxicity of the alloys showed that the extracts of the studied alloys are not cytotoxic for fibroblastic cells.

Towards the development of experimental (α + β) Ti-Al-V-Fe alloys

The influence of partial substitution of vanadium with iron and the reduction of aluminium content on the microstructure and hardness of low-cost α + β titanium alloys was evaluated using Thermo-calc simulation, scanning electron microscopy and Vickers hardness testing. The results show that Thermo-calc predictions and microstructural analysis were in good agreement. The beta phase fraction increased with iron addition and no intermetallic phase was found in alloys having both iron and vanadium as beta stabilising elements. The hardness of the low-cost alloys increased with iron content but commercial Ti-6Al-4V alloy has superior hardness in comparison with the low-cost alloys containing 4.5 wt% aluminium and ≤2 wt% Fe.

Applicability of the Øie-Tozer model to predict three types of distribution volume (Vd) in humans: Vd in central compartment, Vd at steady state, and Vd at beta phase.

This study aimed to investigate the applicability of the Øie-Tozer model to predict human distribution volume (Vd) in the central compartment (V1 ), Vd at steady state (Vdss ), and Vd at beta phase (Vdβ ) based on animal Vd. Twenty compounds that have a human V1 /Vdss of 0.053-0.66 were selected from the literature. After intravenous administration of the compounds at 0.1 mg/kg to rats, dogs, and monkeys, plasma concentrations were determined, and pharmacokinetic parameters were obtained by one/two-compartmental analyses. The human V1 , Vdss , and Vdβ were predicted from animal Vd using the Øie-Tozer model, and the predictability was compared with that using proportionality and simple allometry. The Øie-Tozer model was the most reliable method for the overall prediction of Vd and applicable for accurately predicting human V1 , Vdss , and Vdβ (89%, 85%, and 68% of the compounds within a 3-fold error, respectively) when data of monkey for V1 and data of three animal species for Vdss and Vdβ were used. Additionally, the predicted human Vd with the two-compartment model was applicable for predicting pharmacokinetic profiles/parameters in humans after intravenous administration of 18 compounds [except for valproic acid (monophasic elimination profile) and chlorpromazine (deviation: Vdss < V1 )]. The prediction was more accurate than that using the predicted Vdss with the one-compartment model (e.g., underestimation of maximum plasma concentrations: 2 vs 8 compounds within a 3-fold error, respectively). In summary, the Øie-Tozer model was applicable for predicting human V1 , Vdss , and Vdβ , and their predicted Vd with the two-compartment model can lead to accurate pharmacokinetic prediction of compounds that show biphasic elimination.

Enhanced Piezoelectric Performance of Electrospun PVDF-MWCNT-Cu Nanocomposites for Energy Harvesting Application

Piezoelectric principle is one of the popular choices when it comes to mechanical energy recovery and conversion of energy into electrical energy which can be either stored or used straightaway. In general, ceramic-based piezoelectric materials like Lead Zirconate Titanate (PZT) had been the popular choice for piezoelectric devices even though they are brittle in nature and found to be toxic in long uses. At the same time, organic-based Polyvinylidene Fluoride (PVDF) and similar polymeric materials have been used in different applications with an offer of flexibility, lightweight and biocompatibility. One major factor dragging down the usage of organic materials in piezoelectric applications is their poor piezoelectric responses. In this work, authors are reporting the enhanced piezoelectric properties of nanofibers of PVDF in composite with copper nanoparticles and Multiwalled Carbon Nanotubes (MWCNTs). Fourier Transformation Infrared (FTIR) analysis has been carried out for nanofibers and was able to prove the higher beta phase conversion of PVDF in composite nanofibers when compared with pristine nanofibers. Composite nanofibers were later fabricated into a piezoelectric device with two electrodes and have shown a peak voltage of 6.78 V upon a drop test. As a proof of concept, the mentioned piezoelectric device was integrated into a shoe-based prototype where it has shown 18–20[Formula: see text]V energy harvesting upon walking at leisurely pace.

Correction to: Synthesis and characterization of α-Ag2MoO4/β-Ag2MoO4 heterostructure obtained by fast and simple ultrasonic spray pyrolysis method at different temperatures

In this work, microspheres of α-Ag2MoO4/β-Ag2MoO4 were obtained by ultrasonic spray pyrolysis (USP) at temperatures of 400, 500, 600, and 700 °C. Characterizations of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), Raman scattering, and ultraviolet–visible spectroscopy (UV–Vis) were performed on the samples. The beta phase is present in all samples, while the alpha phase forming α/β-Ag2MoO4 appears from 500 to 700 °C. FE-SEM images indicate the tendency of micrometric sphere formation, in which the increase of temperature promotes a smoothing on the surface. The α/β-Ag2MoO4 heterostructure was a better photocatalytic performance on methylene blue dye (MB) degradation than the pure beta phase. The MB was 87% reduced by the pure beta phase and 100% reduced by the α/β-Ag2MoO4 after 45 min of photocatalysis.