This study examines the phase transitions occurring during linear heating of the Zr15Nb alloy through a comprehensive, multi-technique methodology comprising in situ high-energy synchrotron X-ray diffraction (HEXRD), electrical resistance measurements, differential scanning calorimetry (DSC) and thermal expansion analysis, supplemented by ex situ transmission electron microscopy (TEM). The findings reveal a complex sequence of phase transformations and corresponding structural changes over a broad temperature range (from room temperature up to 800 °C). Two distinct body-centered cubic (bcc) β phases βZr and βNbwith closely related lattice parameters are identified. At room temperature, the microstructure is characterized by a mixture of the metastable βZr + ωath phase. Upon heating, βZr progressively decomposes, giving rise to the formation of βNb. TEM observation revealed the cuboidal shape of the ωiso particles, resulting from the high lattice misfit between β and ω phase. The ω solvus temperature is determined to be approximately 555 °C, as evidenced by in situ HEXRD and abrupt changes in the alloy’s thermal and electrical properties. The growth of the α phase occurs after the dissolution of the ω phase, resulting in a pronounced increase in thermal expansion.

The field-Assisted sintering technique (FAST), also known as spark plasma sintering, is a fast consolidation powder metallurgy technique for conductive and non-conductive materials. However, FAST is commonly used for the manufacture of small specimens. The present work presents the feasibility of sintering larger rods of a biomedical Ti-15Mo alloy using FAST. By implementing an adequate die arrangement, long rods of nearly 80 mm in length and 15 mm in diameter were sintered in less than 30 min with a densification above 95%. Power consumption to produce larger samples is compared with that for typical small-processed specimens. However, microstructural features appeared due to the pressure and temperature distributions, inherent to the technique. The results highlight the opportunities and drawbacks of using FAST for the consolidation of larger specimens, while the microstructural and mechanical performance of the as-sintered and post-processed Ti-15Mo rods are given and compared to a conventionally prepared alloy.

transformations in a metastable beta Zr e 12Nb alloy were investigated by high-energy X-ray diffraction (HEXRD) measured simultaneously with thermal expansion in situ during linear heating from room temperature to 800 (cid:1) C. Complementary in-situ methods of electrical resistance and differential scanning calorimetry, which were performed using the same heating conditions as in the HEXRD experiment, provided additional information on the transformation sequence occurring in the Zr e 12Nb alloy. Two bcc phases with a differentlatticeparameter, b Zr and b Nb ,wereobservedintheinvestigatedtemperaturerange and identified using the phase diagram of the Zr e Nb system. In the initial solution-treated condition, metastable b Zr phase and athermal u particles are present in the material. At about 300 (cid:1) C, Nb-rich b Nb phase starts to form in the material and the original b Zr phase gradually disappears. Ex-situ observations of the microstructure using transmission electron microscopy revealed a cuboidal shape of the u particles, which is related to a relatively large misfit between the u and b phases. At 560 (cid:1) C, u solvus was observed, identified by an abrupt dissolution of u particles which was followed by growth of the a phase. © 2023 The Authors. Published by Elsevier B

BackgroundThere is variation in the reported incidence rates of levator avulsion (LA) and paucity of research into its risk factors.ObjectiveTo explore the incidence rate of LA by mode of birth, imaging modality, timing of diagnosis and laterality of avulsion.Search strategyWe searched MEDLINE, EMBASE, CINAHL, AMED and MIDIRS with no language restriction from inception to April 2019.Study eligibility criteriaA study was included if LA was assessed by an imaging modality after the first vaginal birth or caesarean section. Case series and reports were not included.Data collection and analysisRevMan v5.3 was used for the meta‐analyses and SW SAS and STATISTICA packages were used for type and timing of imaging analyses.ResultsWe included 37 primary non‐randomised studies from 17 countries and involving 5594 women. Incidence rates of LA were 1, 15, 21, 38.5 and 52% following caesarean, spontaneous, vacuum, spatula and forceps births, respectively, with no differences by imaging modality. Odds ratio of LA following spontaneous birth versus caesarean section was 10.69. The odds ratios for LA following vacuum and forceps compared with spontaneous birth were 1.66 and 6.32, respectively. LA was more likely to occur unilaterally than bilaterally following spontaneous (P < 0.0001) and vacuum‐assisted (P = 0.0103) births but not forceps. Incidence was higher if assessment was performed in the first 4 weeks postpartum.ConclusionsLA incidence rates following caesarean, spontaneous, vacuum and forceps deliveries were 1, 15, 21 and 52%, respectively. Ultrasound and magnetic resonance imaging were comparable tools for LA diagnosis.Tweetable abstractLevator avulsion incidence rates after caesarean, spontaneous, vacuum and forceps deliveries were 1, 15, 21 and 52%, respectively.

Ti15Mo alloy was subjected to two techniques of intensive plastic deformation, namely high pressure torsion and rotary swaging at room temperature. The imposed strain resulted in the formation of an ultrafine-grained structure in both deformed conditions. Detailed inspection of the microstructure revealed the presence of grains with a size of around 100 nm in both conditions. The microstructure after rotary swaging also contained elongated grains with a length up to 1 µm. Isothermal ageing at 400 °C and 500 °C up to 16 h was applied to both conditions to investigate the kinetics of precipitation of the α phase and the recovery of lattice defects. Positron annihilation spectroscopy indicated that the recovery of lattice defects in the β matrix had already occurred at 400 °C and, in terms of positron trapping, was partly compensated by the precipitation of incoherent α particles. At 500 °C the recovery was fully offset by the formation of incoherent α/β interfaces. Contrary to common coarse-grained material, in which the α phase precipitates in the form of lamellae, precipitation of small and equiaxed α particles occurred in the deformed condition. A refined two-phase equiaxed microstructure with α particles and β grain sizes below 1 μm is achievable by simple rotary swaging followed by ageing.

High resolution scanning electron microscopy (SEM) is capable of imaging omega phase particles. The SEM observation of Ti15Mo metastable beta titanium alloy after ageing at 500 degrees C for 16 h revealed that the material contains coarse beta grains surrounded by grain boundary alpha phase. Thin lamellae associated with alpha phase were observed in grains interior. Most importantly, small ellipsoidal particles with the size of similar to 100 nm were observed due to chemical contrast. Sample for TEM observation was extracted using focused ion beam to prove that these particles belong to isothermal omega phase that evolves during annealing. In the addition, presence of different families of the omega phase in the material was observed by the combination of bright and dark field imaging. Finally, thin lamellae of the alpha phase in the vicinity of grain boundary were observed using TEM.

Gas atomized Ti-15Mo alloy powder was processed by cryogenic milling. Both initial gas atomized and milled powders were consolidated by spark plasma sintering at temperatures ranging from 750 degrees C to 850 degrees C for 1 and 3 min. Microstructure of the sintered samples was studied by scanning electron microscopy (SEM), chemical contamination was determined by carrier gas hot extraction (CGHE) method and phase composition was investigated by X-ray diffraction. Cryogenic milling resulted in severe plastic deformation of initially spherical particles, changing their shape, but without a significant decrease of particle size. The milled powder achieved the full density after sintering at 750 degrees C, while 850 degrees C was required for a full densification of the initial powder. The amount of a phase was higher in the sintered milled powder, while the sintered non-milled powder contained significant amount of (a phase. It was shown that an ultrafine-grained two-phase microstructure can be produced by a combination of cryogenic milling and spark plasma sintering.

Low-alloyed zirconium alloys are widely used in nuclear applications due to their low neutron absorption cross-section. These alloys, however, suffer from limited strength. Well-established guidelines for the development of Ti alloys were applied to design new two-phase ternary Zr alloys with improved mechanical properties. Zr-4Sn-4Nb and Zr-8Sn-4Nb alloys have been manufactured by vacuum arc melting, thermo-mechanically processed by annealing, forging, and aging to various microstructural conditions and thoroughly characterized. Detailed Scanning electron microscopy (SEM) analysis showed that the microstructural response of the alloys is rather similar to alpha + beta Ti alloys. Duplex microstructure containing primary alpha phase particles surrounded by lamellar alpha + beta microstructure can be achieved by thermal processing. Mechanical properties strongly depend on the previous treatment. Ultimate tensile strength exceeding 700 MPa was achieved exceeding the strength of commercial Zr alloys for nuclear applications by more than 50%. Such an improvement in strength more than compensates for the increased neutron absorption cross-section. This study aims to exploit the potential of alpha + beta Zr alloys for nuclear applications.

Biomedical metastable alloy Ti-xNb-7Zr-0.8O with a compositional gradient of Nb was prepared from elemental powders by a field-assisted sintering technique (FAST). The aim was to investigate phase transformations over a wide range of compositions, facilitating the designing of biomedical Ti alloys. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) investigations revealed that Nb-rich regions retained the β phase, surrounded by transition region consisting of the β and ω phases, while Nb-lean regions consisted of the α and β phases. The Nb concentration, above which formation of the ω phase occurs during cooling instead of the α phase, was determined to be 22 wt%, an important parameter for the low-modulus alloy design. The paper validates the viability of using FAST to prepare heterogeneous Ti alloys permitting to study microstructure over a wide range of compositions. This technique could also be readily used as a high-throughput method for designing other alloy systems. The experimental results were supplemented by calculation of Gibbs energy curves and schematic phase diagrams, which allowed to explain a competition between α and ω formation depending on alloy composition. Such semi-empirical approach can serve as a useful tool for general alloy design, in particular for biomedical Ti alloys.

Ti-15Mo alloy in a metastable beta solution treated condition was processed by equal channel angular pressing (ECAP) at an elevated temperature of 250 degrees C. The resulting microstructure is highly deformed, contains twins and shear bands, but is not ultra-fine grained. Both the initial solution treated material and the material after ECAP were subjected to ageing at 400 degrees C and 500 degrees C in order to study the effect of deformation on phase transformations, namely the a phase precipitation. The phase composition was studied by X-ray diffraction measurement; the microstructure was investigated using conventional EBSD and an advanced method of transmission Kikuchi diffraction (TKD). It was shown that the a phase precipitation is accelerated in areas with higher density of lattice defects, which provide a dense net of preferred sites for nucleation and also fast diffusion paths necessary for accelerated growth. Upon further annealing, discontinuous lamellar coarsening occurs, which had not been previously reported in metastable beta-Ti alloys. The microhardness is governed mainly by the formation of. phase particles. The fraction of omega phase increases during annealing at 400 degrees C and the specimen aged at 400 degrees C/16 h shows the highest value of microhardness of 520 HV for both ECAP and undeformed material. Upon annealing at 500 degrees C, the microhardness is significantly lower.

Ti15Mo metastable beta Ti alloy was solution treated and subsequently deformed by high-pressure torsion (HPT). HPT-deformed and benchmark non-deformed solution-treated materials were annealed at 400 °C and 500 °C in order to investigate the effect of UFG microstructure on the α-phase precipitation. Phase evolution was examined using laboratory X-ray diffraction (XRD) and by high-energy synchrotron X-ray diffraction (HEXRD), which provided more accurate measurements. Microstructure was observed by scanning electron microscopy (SEM) and microhardness was measured for all conditions. HPT deformation was found to significantly enhance the α phase precipitation due the introduction of lattice defects such as dislocations or grain boundaries, which act as preferential nucleation sites. Moreover, in HPT-deformed material, α precipitates are small and equiaxed, contrary to the α lamellae in the non-deformed material. ω phase formation is suppressed due to massive α precipitation and consequent element partitioning. Despite that, HPT-deformed material after ageing exhibits the high microhardness exceeding 450 HV.

Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, the porosity, large grain size and chemical inhomogeneity reduce the fatigue performance below the limits required for utilization in the desired application. Two methods of hot working, die forging and hot rolling, were used for processing of this alloy. Microstructural evolution, tensile properties and fatigue performance of the hot worked material were investigated and compared to the cast material. Microstructural observations revealed that porosity is removed in all hot-worked conditions and the grain size is significantly reduced when the area reduction exceeds 70%. Static tensile properties were improved by both processing methods and ultimate tensile strength (UTS) of 1200 MPa was achieved. Fatigue results were more reproducible in the hot rolled material due to better microstructural homogeneity, but forging leads to an improved fatigue performance. Fatigue limit of 400 MPa was achieved in the die-forged condition after 70% of area reduction and in the hot rolled condition after 86% of area reduction.

Metastable β-Ti alloy Ti-15Mo was prepared by cryogenic ball milling in a slurry of liquid argon. Material remained ductile even at low temperatures, which suppressed particle refinement, but promoted intensive plastic deformation of individual powder particles. Repetitive deformation of powder particles is similar to the multidirectional rolling and resembles bulk severe plastic deformation (SPD) methods. Initial and milled powders were compacted by spark plasma sintering. Sintered milled powder exhibited a refined microstructure with small β-grains and submicrometer sized α-phase precipitates. The microhardness and the yield tensile strength of the milled powder after sintering at 850 °C attained 350 HV and 1200 MPa, respectively. Low ductility of the material can be attributed to high oxygen content originating from the cryogenic milling. This pioneering work shows that cryogenic milling followed by spark plasma sintering is able to produce two-phase β-Ti alloys with refined microstructure and very high strength levels.

OBJECTIVETo evaluate the awareness of fresh mothers regarding the primary prevention of pelvic floor disorders after childbirth. The secondary objective was to identify sources of information, reality of childbirth trauma prevention and attitude to pelvic floor muscle training.DESIGNProspective survey study.SETTINGDepartment of Gynecology and Obstetrics, University Hospital and Medical Faculty in Pilsen, Charles University.METHODSWe included 202 women after a vaginal delivery at our center from 6/2015 to 12/2015. These women completed anonymous questionnaire with six questions.RESULTS83% of respondents were informed regarding the possibility of primary prevention of childbirth, nulliparas were informed better (88%). The main source of information was the Internet (46%), while only 5% of women received information from their doctor. Despite the high awareness of postpartum trauma prevention, less than half of interviewed women actually performed it (35%). The most widely used method was the massage of the perineum (29%), vaginal dilatation balloons were used less (7%) and alternative methods were pursued by only 4% of women. Experience with pelvic floor muscle exercises had 79% of women, while 90% wanted to exercise after the delivery.CONCLUSIONAwareness of mothers regarding primary and secondary prevention of pelvic floor disorders is satisfactory. Nevertheless, the information from doctors is inadequate. Despite high awareness, the antepartum prevention methods are used relatively rarely. The study clearly shows the level of awareness and reality of primary and secondary prevention of pelvic floor disorders in our region.