Beta Phase Research Articles

Polypropylene after thirty years of storage: mechanical proof of heterogeneous aging

The effects of 30 years of storage on the mechanical behavior and hierarchical structure of isotactic polypropylene were characterized. In addition, the structure and properties of the aged samples exposed to subsequent annealing were assessed. The long-term storage caused a dramatic loss of ductility, as manifested by the strain-at-break and impact strength data. The embrittlement was accompanied by a distinct increase in the crystallinity of both the alpha and beta phases, as revealed by X-ray diffraction. The dynamic mechanical behavior was influenced, but insignificantly. A comparison of static and dynamic mechanical data suggests the development of structural heterogeneities in the amorphous phase of the semicrystalline material upon aging. Under mechanical stress, these heterogeneities serve as fracture loci. Subsequent annealing of the aged samples partly reversed the loss of ductility. This indicates healing of the hypothetical irregularities by the thermal treatment. In addition, annealing caused complete transformation of the beta crystallites into the alpha phase. Long-term storage of isotactic polypropylene caused a dramatic loss of ductility, as manifested by the mechanical tensile and impact behavior. The embrittlement was accompanied by an increase in the crystallinity. A comparison of static and dynamic mechanical data suggests the development of structural heterogeneities upon aging that serve as fracture loci under mechanical stress. Subsequent annealing of the aged samples reversed the loss of ductility. This indicates healing of the hypothetical irregularities by the thermal treatment.

Beta phase distribution in Al-Mg alloys of varying composition and temper

The ASTM G67 Nitric Acid Mass Loss Test (NAMLT) is not a universally accurate proxy for intergranular stress corrosion cracking (IG-SCC) susceptibility in Al-Mg alloys. This study aims to understand this discrepancy via an electron backscatter diffraction (EBSD) and ammonium persulfate etching/overlay analysis to characterize the linear grain boundary β coverage (LGBBC). Testing at three NAMLT levels of AA5083-H131, AA5083-H116, AA5083-SHTQ, and AA5456-H116 derived from fracture specimens demonstrates that LGBBC is a more accurate metric to describe the IG-SCC susceptibility, however the correlation degrades for materials with divergent yield strengths. These results provide insights necessary to improve upon ASTM G67.

A Study on Uniaxial Tensile Deformation Behavior of Superelastic Titanium Alloy

A superelastic titanium alloy was subjected to uniaxial tensile deformation at room temperature. The microstructural evolution and deformation mechanisms of the superelastic titanium alloy were investigated by electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Multiple deformation mechanisms including stress-induced martensitic transformation (SIMT), dislocation slip, {332}<113> and {112}<111> mechanical twinning were identified with the increase in uniaxial strain. In the early stage of deformation, a SIMT from the bcc beta phase to orthorhombic martensite phase dominantly occurred. As the deformation proceeded, the phase fraction of the remained martensite which did not return to beta phase obviously increased due to dislocation slip and mechanical twinning. The kernel average misorientation (KAM) value obtained from EBSD data gradually increased with increasing the deformation, indicating that the dislocation evolution was produced by slip. This was well matched with the trend in the full width at half maximum (FWHM) value of the peak profile obtained from XRD data. In addition, the fraction of the {332}<113> twin was lower than that of the {112}<111> twin in the initial specimen. However, the {332}<113> twin rapidly increased compared to the {112}<111> twin as deformation increased. Therefore, it is confirmed that {332}<113> twinning and dislocation slip were the dominant mechanisms during plastic deformation.

Enhanced Electromagnetic Interference Shielding in a Duplex-Phase Mg–9Li–3Al–1Zn Alloy Processed by Accumulative Roll Bonding

High electromagnetic shielding performance was achieved in the Mg–9Li–3Al–1Zn alloy processed by accumulative roll bonding (ARB). The microstructure, electromagnetic interference shielding effectiveness (SE) in the frequency of 30–1500 MHz and mechanical properties of the alloy were investigated. A model based on the shielding of the electromagnetic plane wave was used to theoretically discuss the EMI shielding mechanisms of ARB-processed alloy. Results indicate that the SE of the material increases gradually with the increase in the ARB pass. The enhanced SE can be attributed to the obvious microstructure orientation caused by ARB, and the alternative arrangement of alpha(Mg) phase and beta(Li) phase. In addition, with the increase in ARB pass, the number of interfaces between layers increases and the grain orientation of each layer tends to alignment along c-axis, which is beneficial to the reflection loss and multiple reflection loss of the incident electromagnetic wave.

Microstructure, mechanical properties, and corrosion behavior of new β­type Ti–Mo–Nb based alloys by Mn addition for implant material

Titanium alloys are widely used for biomaterial applications since they have special characteristics, especially better biocompatibility, superior corrosion behavior and lower modulus of elasticity compared to other conventional biomaterials. The development of existing Ti6Al4V alloys by creating new β-type Ti-Mo-Nb based alloys by modifying the addition of the Mn element as a beta phase stabilizer, so that the beta phase structure can have an effect to increase strength and reduce elastic modulus with good biocompatibility and toxicity. In the present work, Ti–Mo–Nb–(x)Mn alloys (x=0, 4, 8, and 12, mass fraction in %) were prepared using an electric vacuum arc furnace with a tungsten electrode. The samples were homogenized at 1050°C for 6 h under a controlled argon atmosphere, and the effects of adding Mn on the mechanical properties and corrosion behavior of the alloys were investigated using X-ray fluorescence spectroscopy, X-ray diffraction, optical microscopy, hardness and ultrasonic tests, and potentiodynamic polarization test. The experimental results show that adding 4 %, 8 %, and 12 %Mn to a Ti–9Mo–6Nb alloy stabilizes the formation of the β-phase titanium, implying that the alloys have similar microstructures but different grain sizes. Potentiodynamic polarization measurements show that an increase of the Mn content in the Ti–9Mo–6Nb alloy decreases the corrosion resistance. At 4 %Mn, the alloy has an elastic modulus of 93 GPa and better corrosion resistance, with a relatively low corrosion rate amounting to 0.00290 mm per year, than those of a commercial Ti–6Al–4V alloy

Action information contributes to metacognitive decision-making

Metacognitive abilities allow us to adjust ongoing behavior and modify future decisions in the absence of external feedback. Although metacognition is critical in many daily life settings, it remains unclear what information is actually being monitored and what kind of information is being used for metacognitive decisions. In the present study, we investigated whether response information connected to perceptual events contribute to metacognitive decision-making. Therefore, we recorded EEG signals during a perceptual color discrimination task while participants were asked to provide an estimate about the quality of their decision on each trial. Critically, the moment participants provided their confidence judgments varied across conditions, thereby changing the amount of action information (e.g., response competition or response fluency) available for metacognitive decisions. Results from three experiments demonstrate that metacognitive performance improved when first-order action information was available at the moment metacognitive decisions about the perceptual task had to be provided. This behavioral effect was accompanied by enhanced functional connectivity (beta phase synchrony) between motor areas and prefrontal regions, exclusively observed during metacognitive decision-making. Our findings demonstrate that action information contributes to metacognitive decision-making, thereby painting a picture of metacognition as a process that integrates sensory evidence and information about our interactions with the world.

Nanoporous layer formation on the Ti10Mo8Nb alloy surface using anodic oxidation

Beta titanium alloys with a low elastic modulus, such as Ti10Mo8Nb alloy, are suitable to relieve the stress shielding effect that occurs in the interface implant/bone. However, these materials are considered bioinert and changing the surface topography is necessary to improve cell adhesion and, consequently, osseointegration. The purpose of this research is the surface modification of Ti10Mo8Nb experimental alloy using anodic oxidation. Ingots of Ti10Mo8Nb experimental alloy were produced by melting in arc melting furnace, cold worked and heat treatment. The anodic oxidation was performed to change the alloy surface using an organic electrolyte under 20 V for 10.8 ks at room temperature. The Ti10Mo8Nb alloy exhibited a beta phase and after the surface treatment, a hydrophilic nanoporous layer of TiO2 was obtained. The anatase phase was observed in the annealed samples around 400 °C without deterioration of this nanostructure. Under these conditions, the sample there was a tendency to improve cellular behavior on the material surface due to their hydrophilic behavior as compared to the sample without surface treatment and the nanoporous layer in the amorphous state. In this sense, the adequate bulk properties together suitable surface response makes Ti10Mo8Nb alloy attractive for biomedical applications.

Titanium sintering science: A review of atomic events during densification

The sintering densification trajectory for titanium powder is identified in terms of the interaction between mass transport processes and microstructure evolution. During initial heating, as surface oxides dissolve, surface diffusion forms bonds between contacting particles without densification. Grain boundaries form in the bonds due to random crystal orientations at the contacts. Except for mixed powder Kirkendall swelling, subsequent diffusion in these interparticle grain boundaries leads to densification. Most importantly, the alpha-beta transformation provides strain, defects, and interfaces that accelerate densification in the 800–1100 °C temperature range. This is below a typical peak sintering temperature. Final densification involves beta phase volume diffusion and grain boundary diffusion. Densification slows due to grain growth and the loss of grain boundary area. Pores close near 92% density to trap impurities and reaction products inside the closed pores, often limiting sintered density to about 95% of theoretical. High final density requires slow heating or long holds at intermediate temperatures to evaporate impurities prior to pore closure. The master sintering curve is a means to link densification to process parameters without concern over detailing this cascade of transport mechanisms and microstructure changes.

A study on the mechanical properties and corrosion behavior of the new as-cast TZNT alloys for biomedical applications.

In this study, four different TZNT based alloys, (Ti55Zr25Nb10Ta10, (Ti55Zr25Nb10Ta10)99.5Fe0.5, (Ti55Zr25Nb10Ta10)98Sn2, and (Ti55Zr25Nb10Ta10)98.5Ag1.5, (at. %), designated TZNT, TZNT-Fe, TZNT-Sn, TZNT-Ag, respectively) are produced by non-consumable vacuum arc melting and suction casting. These alloys using the d-electron alloy design method and considering the criteria of [Mo]eq and (e/a) ratio for β-phase Ti alloys are designed. The microstructure, mechanical properties, and corrosion behavior of the alloys are investigated via optical microscopy, scanning electron microscopy, X-ray diffraction, nanoindentation, and electrochemical tests. The designed alloys exhibit dendritic morphology, however, the TZNT-Ag alloy indicates a more homogenous microstructure after suction casting. X-ray diffraction analyses reveal not only the beta phase in the TZNT, TZNT-Fe, and TZNT-Ag alloys, but also beta lean/beta rich separation in the TZNT-Sn alloy. In addition to the microstructural features, the new TZNT alloys show very high ductility upon cold compressive deformation, as well as the lowest Young's modulus (65.54±1.7GPa, P<0.05) is achieved in TZNT-Ag alloy. Furthermore, the compressive yield stress to Young's modulus (Ycys/E) ratio of the designed alloys is in the range of 0.92-1.08%. In terms of corrosion behavior, Ag increases the corrosion resistance of the TZNT alloy in Ringer's solution. As a result, owing to the effect of Ag on the optimization of the mechanical properties and corrosion resistance of the TZNT alloy, the as-cast Ag-containing TZNT alloy can be developed to be a promising candidate for biomedical applications.

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.

Silica nanoparticles surface charge modulation of the electroactive phase content and physical-chemical properties of poly(vinylidene fluoride) nanocomposites

Composites based on a piezoelectric polymer (PVDF) doped with different silica nanoparticles (SiNPs) content (8, 16 and 32 wt%) and functionalization (WF-without, NF-negative and PF-positive) have been investigated. Composite films were prepared by solvent casting and melt crystallization to investigate the effect of the presence of the SiNPs on the physico-chemical characteristics and, in particular, in the nucleation of the electroactive β-phase of the polymer. It is shown that the introduction of the SiNPs allows to increase water surface angle up to 34% with respect to α-PVDF, as well to increase the elastic modulus. Filler content and type have an important effect on the nucleation of the electroactive beta phase content and the dielectric properties of the composites, the larger values of both being obtained for positively surface charged nanoparticles. It is concluded that, taken into consideration the overall properties of the composites, the SiNPs-PF/PVDF nanocomposites with 8 wt% filler content offer a promising approach for applications due to the improvement of the electroactive phase of PVDF.

RANCANG BANGUN GAME TREASURE OF LABYRINTH DENGAN ALGORITMA BACKTRACKING BERBASIS ANDROID

Games are one of the entertainment media which is the choice of almost everyone to get rid of boredom or just fill in spare time, there are also games used as hobbies and moreover games are now used as electronic sports (e-sports). Currently the game has many types of games, one of which is a type of puzzle game (puzzle). One puzzle game is a maze game. The labyrinth is a puzzle that has a complex branching form and has many dead ends. At the moment there are many labyrinth type games, but rarely are labyrinth games equipped with characters, enemies and a dynamic maze that can change if the game is repeated. To create a labyrinth game that has a dynamic labyrinth arena requires a labyrinth generator or can be called a labyrinth generator by utilizing the backtracking algorithm. This algorithm is powerful enough to be used in some problem solving and also to provide artificial intelligence in the game. The software methodology used in making games is the GDLC (Game Development Life Cycle). GDLC is a game development model that adopts an iterative approach consisting of 6 development phases, starting from the innitiation, pre-production, production, testing, beta and realese phases. for the generation of the labyrinth arena using the Backtracking algorithm while for testing this game uses the UAT (User Acceptment Test). The results of this study in the form of an adventure game based on a maze puzzle that is applied to mobile android. This game is played to train players in problem solving and entertainment facilities.Keywords: Puzzle Game, GDLC (Game Development Life Cycle), Backtracking Algorithm, Android

Hydrothermal Synthesis and Photocatalytic Property of Sn-doped β-Ga2O3 Nanostructure

Tin (Sn)-doped beta phase gallium oxide (β-Ga2O3) nanostructures at different Sn concentrations (0 to 7.3 at%) are synthesized using a facile hydrothermal method. The Sn-doped β-Ga2O3 nanostructures are characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and absorbance spectroscopy. In addition, their photocatalytic activity is evaluated by observing methylene blue degradation under ultraviolet light (254 nm) irradiation. The photocatalytic activity of the Sn-doped (0.7 at%) β-Ga2O3 nanostructures is significantly enhanced compared to that of intrinsic β-Ga2O3 nanostructures due to the elevated charge separation. Excessive Sn concentrations (exceeding 2.2 at%) above the solid solubility limit of the Sn in β-Ga2O3 nanostructures lead to SnO2 and SnO precipitation. The presence of SnO2 and SnO degrades the photocatalytic efficiency in the β-Ga2O3 nanostructures. The results suggest new opportunities for the synthesis of highly effective β-Ga2O3-based photocatalysts for applications in environmental remediation, disinfection, and selective organic transformations.

Plastic deformation of beta-Ti-Mo alloys with isothermal omega phase

Aging of metastable beta-Ti alloys leads to the precipitation of omega phase, resulting in a significant loss in ductility (omega brittleness). This presentation reports the results of 3D observations of isothermal omega phase by an orthogonal FIB/SEM system. It was revealed that the shape of omega phase particles varies with the particle size. By serial sectioning, it was possible to obtain a 3D image for the volume of several micrometer cube containing numerous omega particles. The volume fraction of omega phase was qualitatively determined. The value was much lower than the previous investigation by X-ray diffraction by Hickman in 1969. The SEM and TEM revealed the formation of shear bands in the cold rolled samples, where the shearing of omega phase and transformation into beta phase while maintaining the depletion of Mo was found. After the HPT deformation, white etching layers are formed near the median plane of the disc, where the omega phase particles were absent and exhibit significantly lower hardness values. These findings may help to clarify the cause of brittleness in beta Ti alloys with isothermal omega phase.

Improvement of high temperature performance of titanium matrix composites by constructing hierarchical microstructure

The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure, such as hierarchical microstructure and nano microstructure. In order to significantly enhance the creep resistance of titanium alloys, one two-level hierarchical microstructure with micro-TiB whiskers (TiBw) and nano Ti5Si3 reinforcements were constructed to form the modified composites by powder metallurgy combining with in-situ synthesis and precipitation. The micro TiBw reinfrocement were in-situ synthesized around titanium matrix particles, which formed the first scale network microstructure. The nano Ti5Si3 particle were precipitated and distributed in the beta phase around alpha phase which formed the second network microstructure. The results showed that the high temperature strength has been significantly enhanced. The tensile strength at 550oC for Ti6Al4V matrix composites is increased to 1050MPa. Moreover, the creep rate of the modified Ti6Al4V matrix composites was remarkably reduced by an order of magnitude compared with the conventional Ti6Al4V alloys at 550 oC, 600 oC, 650 oC under the stresses between 100 MPa and 350 MPa. Moreover, the rupture time of the composites increased by 20 times, compared with Ti6Al4V alloys at 550 oC/300 MPa. The superior creep resistance can be attributed to the two-level hierarchical microstructures and the two-scale reinforcements. The micro-TiBw reinforcement in the first network boundary contributed to creep resistance primarily by blocking grain boundary sliding, while the nano-Ti5Si3 particles in the second network boundary mainly by hindering phase boundary sliding. In addition, the nano-Ti5Si3 particles were dissolved to smaller-sized Ti5Si3 particles during creep deformation due to high temperature and external stress, which can further continually enhance the creep resistance. Finally, the creep rate during steady-state stage was unprecedentedly decreased, not stable or increased, which manifested superior creep resistance of the composites. The calculated results indicated that the dislocation climb is the dominant mechanism for the composites tested at 550 oC/(250-350) MPa and 650 o C/(100-250) MPa.

Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator

Microstructure dependence on mechanical properties were investigated for Ti-17 forged at temperatures between 700 and 850 ˚C with deformation ratio from 33 to 80 %, and solutiontreated at 800˚C for 4 hours and aged at 620 ˚C for 8 hours. The microstructure was observed after solution and aging treatments. The volume fraction and the size of the primary alpha phase was controlled by solution treatment temperature, not forging temperature and deformation ratio. Forging temperature affected the morphology of grain boundary (GB) alpha phase. Deformation ratio affected the grain size and the aspect ratio of the horizontal and vertical grain size of the prior beta phase. The tensile strength was investigated at room temperature, 450, and 600 ˚C. Forging temperature and deformation ratio did not affect the tensile strength because there is no large difference of the volume fraction of the alphaphase. On the other hand, the elongation and the reduction of area increased with increase of the aspect ratio of the prior beta grains; that means, increase of the deformation ratio. Raising of forging temperature also increased elongation and reduction of area due to the film-like GB alphaphase.

Achieving high strength and low Young’s modulus by controlling the beta stabilizers content in Ti-Nb-Ta-Zr-O alloys

High strength and low Young’s modulus is the desired combination of mechanical properties for the endoprostheses material. Metastable beta titanium alloys are promising materials for this application. In this study, four Ti-xNb-6Ta-7Zr-0.7O (wt.%) alloys were prepared where Nb content ranged from 26 to 35 wt. %. All alloys contained pure beta phase. The high oxygen content causes high microhardness (330 HV), hence also the strength, while decreasing content of Nb leads to lower electrons per atom (e/a) ratio. The e/a ratio affects the Young’s modulus which is highest (76 GPa) in Ti-35Nb-6Ta-7Zr-0.7O alloy with e/a=4.31 and the lowest (64 GPa) in Ti-26Nb-6Ta-7Zr-0.7O with e/a=4.24. Such evolution of Young’s modulus is in accordance with existing literature data, however, in comparison with other works, the Ti-26Nb-6Ta-7Zr-0.7O alloy shows double microhardness when compared to alloys with similar Young’s modulus. Therefore, the approach of using controlled oxygen content for alloy design is very promising for development of biocompatible metastable beta Ti alloy for endoprostheses production.

Nano-scale characterisation of tri-modal microstructures in TIMETAL® 575

TIMETAL® 575, developed by Titanium Metals Corporation (TIMET), is a high strength forgeable α+β titanium alloy with comparable density, beta transus temperature and processing characteristics to Ti-6Al-4V but with enhanced static and fatigue strength primarily aimed at aero-engine disc or blade applications. Recent research on this alloy has focussed on microstructure evolution as a means to optimise mechanical behaviour and it has been concluded that a solution heat treatment followed by an ageing step yields a resulting “tri-modal” microstructure, consisting of equiaxed primary α and bi-lamellar transformation product containing nano-scale “tertiary alpha” laths, which appear to provide an excellent balance of strength and ductility. The key objective of the work presented here is to characterise this complex nanoscale microstructure in detail at various stages of alloy processing. For that purpose various advanced and recently developed transmission electron microscopy (TEM) techniques have been used. These include alpha and beta phase mapping Precession Electron Diffraction (PED), overall microstructure imaging with conventional BF and DF TEM, distinction of fine phase detail with high angle annular dark field (HAADF) scanning TEM (STEM), and correlation of the nanostructure to the elemental distribution using scanned Electron Energy Loss Spectroscopy (EELS).

Deformation behaviour of beta phase with similar chemical composition in beta and alpha+beta titanium alloys

Twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) in β titanium alloys have been attracting significant interest, since they offer the possibility to provide work hardening and thus, ductility. Here a quaternary Ti-Al-Cr-Mo metastable β alloy has been designed with an excellent combination of strength ductility that exploits the TWIP and TRIP effects. Its engineering yield strength, tensile strength and total elongation are 737 MPa, 999 MPa and 24%, respectively. In order to increase the yield strength but retain ductility, an attempt has been carried to design an α+β alloy with a bimodal microstructure. The composition of the β phase in the α+β alloy was tuned to provide deformation twinning of the β phase. The content of the major α and β stabilising elements, i.e. Al, Cr and Mo, in the β phase of the α+β alloy was similar to the β alloy, but the deformation twinning was not observed in the β phase. It is suggested that this may be due to over-stabilisation of the β phase and/or to the different stress/strain and dislocation distributions in the α+β alloy caused by the presence of β phase.

Effects of Mo segregation on Charpy absorbed energy in Ti-12Mo alloys

Beta phase stabilizing elements such as Mo have strong tendency to segregate. We have introduced swirly type segregation of Mo in Ti-12Mo (mass %) alloy through groove bar rolling. After solution treatment and low temperature aging, hard omega phase was precipitated heterogeneously, which improved the room temperature tensile elongation values without sacrificing tensile strength. In this study, the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy was investigated in Ti-12Mo alloy. Samples with two types of segregation were prepared; namely, swirly segregation in bar rolled sample and layered segregation in plate rolled sample. For comparison, we have also prepared Ti-12Mo bar samples with lesser Mo segregation, through high temperature thermomechanical treatment. Charpy impact tests were carried out at room temperature, 373 K and 473 K, respectively, using the samples after aging to introduce isothermal omega-phase. The samples with the segregation exhibited higher Charpy absorbed energy, especially at higher temperature of 473 K, while the sample with the swirly segregation showed higher Charpy absorbed energy than that with the layered segregation. The sample with lesser Mo segregation exhibited brittle intergranular fracture surface after Charpy testing. On the contrary, samples with Mo segregation exhibited ductile transgranular fracture surfaces.