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Ti-55531 (Ti-5Al-5Mo-5V-3Cr-1Zr) is near β titanium alloy, which plays a significant role in manufacturing landing gears and flap tracks in the aerospace industry. This study aims to find out an optimal heat treatment to obtain an excellent balance of strength, ductility and fracture toughness. For this purpose, the Ti-55531 alloy was subjected to solution plus aging treatments and mechanical properties tests. Optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) were adopted to observe the microstructural evolution including morphology, distribution and size. Standard tensile and compact tension (CT) tests were carried out to obtain the yielding/tensile strength (YS, TS), elongation (EL) and fracture toughness (KIC) of Ti-55531 alloy. The effects of solution temperature, aging temperature and time on the microstructural evolution and fractography were analyzed. The relationships between the mechanical properties and microstructures were qualitatively described. The influencing mechanism of plastic deformation and crack propagation path on the KIC were discussed. Simultaneously, the values of YS and KIC were predicted based on mechanical property models, the predicted values were compared with tested data. Finally, an optimal heat treatment was proposed for the Ti-55531 alloy, to obtain a good balance of strength, ductility and fracture toughness.

A novel method is proposed to determine the constitutive relationship for a laminated composite by considering the strain-dependent microhardness of the heterostructure layers and bonding regions. A theoretical model is deduced to provide an analytical basis for the proposed method. The elemental and microhardness distributions of the heterogeneous layers and bonding regions of the TA1/Al1060/SS430 laminated composite were studied. Laws describing the variation of the microhardness of the heterogeneous layers and bonding regions with strain were obtained. A constitutive relationship for the heterostructure layers and bonding regions of the laminated composite was obtained. V-shaped bending finite-element analysis of a laminated composite using the determined constitutive relationship was conducted to verify its reliability. The proposed novel method may become a promising approach to study the plastic deformation behavior of laminated composites.

The effect of microstructure heterogeneity on flow instability is investigated during isothermal compression. The mechanism of plastic flow instability is studied from the perspective of the strain mode and geometrical orientation dependence of microstructure. It is found that the instability criteria underestimate the range of unsafe processing region of lamellar microstructure due to its stronger trend to flow instability. The key factors are the geometrical orientation and colony size of lamellar microstructure. In the colonies with hard geometrical orientation, deformation resistance is big since only the pyramidal slip system can be operated. The difference of the deformation resistance among colonies can reach 49% in a primary β grain. The incompatibility of flow among various colonies promotes the generation of micro shear bands in colonies with hard geometrical orientation, which facilitates the slip transmission across α/β interfaces and weakens the Hall-Petch strengthening effect. The large colony size facilitates the rapid expansion of micro shear bands leading to the continuous softening of colonies, which strengthens the strain localization and accelerates the occurrence of flow instability. The critical value of Semiatin's model is modified to 4 for lamellar microstructure. Based on this research, a method to confirm more precise unsafe processing regions of titanium alloys of different microstructures is proposed.

Folding defect is one of the most important forging defects, which can deteriorate the surface quality, mechanical properties, and material utilization of forged parts. In this work, the common folding defects in die forging were classified into three typical types: local-loading-type folding, confluence-type folding, and bending-type folding. Three simple Eigen experiments were employed to analyze the formation mechanisms and rules of three typical types of folding accordingly. By FE simulation, the formation mechanisms of three typical types of folding defects were analyzed based on the evolution of the velocity field. In addition, the effects of geometric and forging parameters on each type of folding defect were investigated by uniform experiment design. Especially, a quantitative folding index was applied to uniformly evaluate the formation possibility and severity of folding defect for any samples whether producing folding or not. It is found that the local-loading-type folding is produced by the formation and collapse of a step, which is sensitive to the reduction amount but insensitive to the feed amount. The confluence-type folding is formed due to the local lack of material, which is sensitive to the reduction degree and insensitive to the rib width and billet height in this work. The bending-type folding is mainly formed by the geometric instability of workpiece during the forming process, which is sensitive to the reduction degree and insensitive to the geometric parameters of billet.

Ti/Al laminated composite fabricated by explosive welding has received widespread attention due to their potential in achieving excellent performance. However, investigations on the crack evolution...

This work focuses on the plastic deformation behavior and microstructure evolution in high temperature sheet bulk forming of 2219 aluminum alloy. Uniaxial compression tests were carried out along the normal direction (ND), transverse direction (TD) and rolling direction (RD) of an annealed rolled sheet which has brick-like grains but weak texture. Electron backscattered diffraction (EBSD) was employed to observe the microstructure after compression deformation. Experimental results show strong anisotropy in plastic flow in spite of non-prominent anisotropy in strength. Meanwhile, grain refinement mechanisms transform from geometric dynamic recrystallization (GDRX) in ND compression to discontinuous dynamic recrystallization (DDRX) with enhanced particle stimulated nucleation (PSN) effect in TD and RD compressions. Grain morphology has little effect on the plastic anisotropy. However, the heterogeneous deformation associated with the distortion of brick-like grains in compression accounts for the diverse microstructural developments to a large extent.

Background The global trigger tool is a method of retrospective medical record review that identifies possible harm in hospitalized patients using "triggers". Elderly patients with multiple co-morbid illnesses are especially vulnerable to adverse drug events (ADEs) that have high prevalence rates. Objective The purpose of this study was to develop an appropriate trigger tool to detect ADEs in Chinese geriatric inpatients by combining a literature review with the Delphi method. Setting Chinese geriatric inpatients. Methods Two steps were used to develop the trigger tool. First, we conducted a comprehensive literature review for existing ADE triggers (adult or elderly) to form the initial triggers for the Delphi process. Second, a group of clinical experts, including physicians, clinical pharmacists and nurses, was established to score candidate triggers for utility according to the usefulness and feasibility of implementing triggers in clinical practice. Main outcome measures The frequency of the full mark, arithmetic mean and coefficient of variation of each trigger. Results An initial set of 51 triggers was selected by literature review for evaluation. The group of experts was composed of 18 clinical experts: 13 physicians, 4 clinical pharmacists, and 1 nurse. Based on the two-phase Delphi process, 42 triggers in five categories (laboratory index, plasma concentration, antidotes, clinical symptoms and intervention) were retained. Conclusion The 42-trigger tool was developed to identify ADEs in Chinese geriatric inpatients. A pilot study that tests the list of triggers to identify ADEs in Chinese geriatric inpatients is the next step for establishing a specific trigger tool for Chinese geriatric inpatients.

For a two-phase titanium alloy, the tensile and damage tolerance properties exhibited in tri-modal microstructure were investigated and compared to the same properties exhibited in widmanstatten and bimodal microstructures. These investigations and comparisons were conducted by analyzing the microstructure characteristics and their influences on deformation behavior and fracture features. The results show that the tri-modal microstructure exhibits superior strength and plasticity that are close to bimodal microstructure and remarkably higher than the widmanstatten microstructure. The underlying reason is that the multiple types of interfaces and refined grains of tri-modal and bimodal microstructures produce greater interface strengthening and better overall deformation homogeneity than the widmanstatten microstructure. Furthermore, the better deformation homogeneity also contributes to suppressing the low-cycle fatigue crack initiation of tri-modal microstructure. Besides, the unique lamellar α in tri-modal microstructure with disordered distributions on both geometric and crystallographic orientations effectively hinders the fatigue crack propagation. Thus, the low-cycle fatigue life (the number of reversals to failure) of tri-modal microstructure is the longest, which is 3.93 times as long as that of widmanstatten microstructure and 1.12 times as long as that of bimodal microstructure. For the fracture toughness, the fracture crack paths of bimodal and tri-modal microstructures with the small sized grains present far lower fluctuation and tortuosity compared to those of widmanstatten microstructure, which means lower energy consumption. However, the crack path of tri-modal microstructure is still more deflected than that of bimodal microstructure due to the contribution of the disorderly distributed lamellar α, which increases the energy consumption to some extent. Thus, the fracture toughness of tri-modal microstructure is lower than the widmanstatten microstructure but higher than the bimodal microstructure. These results indicate that tri-modal microstructure exhibits more excellently combined tensile and damage tolerance properties compared to the other two microstructures.

The microstructural evolution of a Ni-based superalloy under interrupted hot compressive deformation with different cooling rates in the inter-pass stage is investigated. It is found that metadynamic recrystallization (MDRX) in the inter-pass stage is more sensitive to the accumulated strain than the deformation temperature which is above the recrystallization temperature. The variations of both the grain distribution and the texture intensity caused by MDRX during the inter-pass stage result in variations of the yield stress (YS) and the work hardening (WH) rate in each stage. Results also show that the MDRX process in the inter-pass stage has a considerable influence on the final microstructure of three-pass compression. The final grain distribution is more uniform, and the compression texture gradually transforms into recrystallization texture with an increasing degree of MDRX. In order to predict the MDRX fraction in the inter-pass cooling stage, a modified kinetic equation is established, which can reasonably predict the MDRX behavior under multi-pass compression with different conditions in the inter-pass stage. Meanwhile, the influence of the inter-pass cooling stage on the mechanism of dynamic recrystallization (DRX) is studied. It is universally acknowledged that the discontinuous dynamic recrystallization (DDRX) process is the major deformation mechanism for the Ni-based superalloy. However, the continuous dynamic recrystallization (CDRX) process is promoted in the compression stage with a decrease of the cooling rate in each inter-pass stage. Keywords: Cooling rate, Hot compression test, Kinetic equation, Ni-based superalloy, Recrystallization

The microstructural evolution, mechanical properties and fracture mechanism of a Ti–5Al–5Mo–5V–3Cr–1Zr (Ti-55531) alloy after solution (760–820 °C) plus aging (580–640 °C) treatments were investigated. The results show that the volume fraction of the primary α (αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800 °C for 2 h plus aging of 640 °C for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.

In this work, the micro-scale damage development and crack propagation features of TA15 titanium alloy with tri-modal microstructure consisting of equiaxed α (αp), lamellar α (αl) and β transformed matrix α (βt) were firstly investigated. On that basis, the dependences of fracture toughness of tri-modal microstructure on microstructural parameters were discussed. The results indicate that in the damage and fracture of tri-modal microstructure, voids mainly nucleate and grow up at the triple junctions and the interfaces of αp/αp, αp/βt and single-αl/βt due to the micro-scale strain incompatibility at these locations. By internal necking or local shearing connection with these voids, the main crack achieves an increment. It leads to two main categories of crack paths, i.e., the connection-type path caused by the connection behavior and the natural-extension-type path progressing through voids after the connection with voids. The connection-type path exerts greater influence on the fracture toughness than the natural-extension-type path. Moreover, as for the connection-type path, it can also be classified into two sub-categories, i.e., the internal necking connection-type path and the local shearing connection-type path. As far as the energy consumption is considered, more internal necking connection-type path is favorable for improving the fracture toughness, while more local shearing connection-type path is detrimental. Besides, the above void evolution and crack propagation behavior will affect the tortuosity of crack path to some extent, which will also change the overall energy consumption and final fracture toughness. As for the dependence of fracture toughness on microstructural parameters, it is found that with the increase of αp content, the proportion of low-energy-consumed crack paths (local shearing across αp and colony-αl) increase and the crack path tortuosity decreases, both of which reduce the energy consumption and result in the continuous reduction of fracture toughness. As the αl content increases, the disorderly distributed single-αl significantly increases at lower αl content, which improves the crack path tortuosity and energy consumption. However, at a higher level of αl content, single-αl decreases dramatically and the content of colony-αl becomes high, which reduces the crack path tortuosity and energy consumption remarkably. So, the fracture toughness first increases and then decreases with the increase of αl content.

The folding defect is one of the most common flow-induced defects in the die forging, and the prediction of folding defects is of great significance in product and processing design. To this end, a versatile approach for the prediction of three typical types of folding defects was developed in this work. Firstly, the folding defects in die forging are classified into three types: confluence-type, bending-type, and local-loading-type, according to the material flow characteristics during their development. Then, three simple Eigen experiments and the corresponding FE models are developed to capture the formation processes of these three typical of folding types. On these bases, a versatile prediction approach is established and verified for all three typical folding defect types. This approach is realized by combining a folding index, judging criteria, and a mathematical model relating the folding index and formation parameters. A folding index based on the integration of the strain rate over the free surface of workpiece is proposed, which can evaluate the risk of all three typical types of folding. The corresponding judging criteria for folding defects based on folding index are determined by multiple uniform experiments for each type of folding defects. The mathematical model relating the folding index and forging parameters can be developed by common metamodeling techniques based on FE simulation results; the response surface methodology is employed as an example in this work. Compared to informed folding prediction methods, the present approach presents the following main advantages: (1) wider application scope to all typical types of folding in die forging, (2) no geometrical parameter dependence, (3) the ability to apply the folding index not only to predict folding defects, but also to serve as an objective function to optimize forging parameters to minimize the risk of folding. The results will provide an important tool for the workpiece and processing design to improve the forming quality during die forging.

The cast preformed forming process (CPFP) is increasingly considered and applied in the metal forming industries due to its short process, low cost, and environmental friendliness, especially in the aerospace field. However, how to establish a unified model of a non-uniform as-cast billet depicting the flow stress and microstructure evolution behaviors during hot working is the key to microstructure prediction and parameter optimization of the CPFP. In this work, hot compression tests are performed using a non-uniform as-cast 42CrMo billet at 1123–1423 K and 0.01–1 s−1. The effect laws of the non-uniform state of the as-cast billet with different initial grain sizes on the flow stress and microstructure are revealed deeply. Based on experimental results, a unified model of flow stress and grain size evolutions is developed by the internal variable modeling method. Verified results show that the model can well describe the responses of the flow stress and microstructure to deformation conditions and initial grain sizes. To further evaluate its reliability, the unified model is applied to FE simulation of the cast preformed ring rolling process. The predictions of the rolling force and grain size indicate that it could well describe the flow stress and microstructure evolutions during the process. Keywords: Cast preformed forming process, Flow stress, Grain size, Non-uniform as-cast 42CrMo billet, Ring rolling, Unified model

How to form high-quality transverse inner ribs through power spinning is a key issue for complicated integrated curved generatrix parts with transverse inner ribs. In this study, the forming characteristics and laws during the power spinning process were investigated using a finite element simulation based on the orthogonal design method. The results show that the transverse inner rib distributes homogeneously along the circumferential direction but inhomogeneously along the generatrix direction. Depressions occur easily in the middle zone of the rib (MZR). The roller nose radius is the most significant parameter of the MZR underfill degree. A larger roller nose radius is helpful to decrease the MZR underfill degree. Furthermore, the preformed billet thickness also plays a vital role in the underfill degree of the front zone of the rib and the back zone of the rib, as well as the depression degree of the outer surface of the rib. By combining the rib-filling characteristics and laws, the optimized forming process window for obtaining high-quality inner ribs was obtained by regression analysis, thus laying a basis for improving the forming quality of curved generatrix parts with transverse inner ribs in power spinning.

Revealing the microstructural parameters-mechanical properties relationship is very critical for the microstructure tailoring and properties optimization of titanium alloy. In this work, the dependence of mechanical properties on microstructural parameters of TA15 titanium alloy with tri-modal microstructure was investigated. The results indicate that at a certain lamellar α (αl) content (28%), both of yield strength (σ0.2) and ultimate tensile strength (σb) decrease continuously with the increase of equiaxed α (αp) content, while the decrease speed slows down at higher αp content. At a certain content of αp of 20%, σ0.2 and σb both increase first and then decrease as the content of αl increases. The above effect laws result from the competition between the softening effect caused by increasing the softer αp and αl contents and the strengthening effect relating to αl/βt interfaces and βt hardening. As for the elongation (δ) and reduction of area (Φ), they show an increase trend with αp content increasing at a certain αl content of 28%. However, they decrease first and then increase with αl content increasing at a certain αp content of 20%. The early plasticity decrease at lower αl content is due to the popular rapid void nucleation and cleavage fracture along αl/βt interfaces. When αp or αl content increases to higher level, the deformation compatibility and homogeneity improves, which suppress the rapid void nucleation and cleavage fracture along αl/βt interfaces. Meanwhile, the fracture mechanism changes from the coexistence of void coalescence and cleavage fracture to the void coalescence dominated fracture, thus the plasticity increases. Moreover, a back-propagation neural network model was developed to correlate the mechanical properties with microstructural parameters of tri-modal microstructure. The prediction results suggest that better combination of strength and plasticity can be achieved by controlling the contents of αp and αl in the range of 10–15% and 22–27%, respectively.

Unveiling the quantitative influence of the induced eddy current in electromagnetic forming (EMF) is of great significance to realize the precision control of the forming process. To this end, a semi-phenomenological model for predicting the current-carrying dynamic deformation behaviors of aluminum alloy is established by introducing a rate-dependent electroplasticity (EP) model and an elastic thermal expansion model into the high-strain-rate constitutive model. In the modeling process, the electroplastic energy density (EPED), which is a function of prestrain and current density, is defined as the dominant factor of EP-induced stress drop and its threshold value is determined. Moreover, a rate-dependent factor is formulated to consider the effect of wide-range strain rate variation on EP-induced stress drop. Applied to uniaxial-stress EMF process, the present model exhibits preferable prediction accuracy by comparing the predicted results of analytical calculation with experimental ones. The present model captures the characteristic stress responses of EMFed samples, i.e. monotonic strain hardening followed by long-range flow softening. It is found that the peak stress and EP softening ratio both increase with EPED, which can be attributed to the combined influences of increased current density, electric resistivity and acceleration on the competition between strain rate hardening and EP induced softening.

Bifunctional oligomers with both reducing and stabilizing functionalities were prepared and successfully applied to the preparation of silver colloids of around 2 nm size without employing a strong stabilizer such as S and P, which was quite difficult to achieve. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were performed to determine the morphology and particle size of the Ag colloids. UV-vis spectroscopy and X-ray absorption spectroscopy (XAS) were implemented to investigate the oxidation state of the Ag colloids. Synthesis parameters such as the density control of the ligating functionalities, the propinquity of the reducing and stabilizing groups, the extent of ligand stabilization and the reducing rates were found to have important effects on the formation and stabilization of Ag colloids. The as-synthesized Ag colloids were very stable even after being deposited on silica; then, they were subjected to calcination to get rid of the organics, which afforded Ag NPs (1.9–3.5 nm) on silica with narrow size distribution. These Ag NPs performed excellently in catalytic 4-nitrophenol reduction with conversion of up to 98% within 10 min. Furthermore, the Ag nanoparticles were quite stable and exhibited excellent reusability for seven successive reaction cycles without obvious decay. The straightforward synthesis of the ultra-small and stable Ag NPs has the potential for applications in the synthesis of other supported late transition metals.

A combination of scanning electron microscopy and electron backscatter diffraction is used to investigate the deformation in the fatigue crack tip plastic zone and its role in the crack propagation of Ti-6Al-2Zr-1Mo-1V alloy with a tri-modal microstructure. The results show that heterogenous slip and secondary micro-cracks are the main features of the fatigue crack tip plastic zone. These features play important roles in fatigue crack propagation. In particular, the unique lamellar α in the tri-modal microstructure can deflect and delay the crack propagation effectively, thus, improving the fatigue life.

Objectives The purpose of this study was to describe the level, preventability and categories of adverse events (AEs) in Chinese geriatric patients identified by medical record review using the Global Trigger Tool. The applicability of the GTT was also assessed to explore possible modifications for trigger tools. Methods The study was conducted at a 4300-bed tertiary teaching hospital. Twenty randomly-selected medical records for patients over 60 were reviewed every 2 weeks from January 1 2015 to December 31st, 2015. We studied 480 medical records in total. Two trained specialists reviewed the presence of AEs using 43 triggers, and a physician reviewed and validated the findings. The outcome measures included the number of AEs per 1000 patient days, AEs per 100 admissions, the percentage of entries with at least 1 AE and AE categorisation. Also, we carried out a descriptive analysis of the suspected factors of AEs, such as age, gender, length of stay, surgery. Results A total of 610 AEs were detected in the 480 medical records reviewed, corresponding to 127 injuries per 100 admissions. The number of AEs per 1000 patient days was 22.43. AEs occurred at least once in 329 (68.54%) patients. The rate of care harms ranked highest of all AEs, followed by the rate of medication harms and surgical harms. Patients with a more extended hospital stay or surgery was more likely to experience AEs. However, there was a negative correlation between age and the rate of AEs. Conclusion The Global Trigger Tool was a useful method for detecting the characteristics of AEs in geriatric patients in a Chinese tertiary teaching hospital. To improve patients' safety, this tool should be incorporated into routine screening systems.

In this paper, the microstructure development and flow behavior in the near isothermal forming of two-phase titanium alloys were studied through designing an off-equilibrium analog experiment. The results show that deformation decreases the volume fraction of primary alpha ( α p ) phase significantly at high temperature. This can be ascribed to the occurrence of dynamic transformation of α p →β by calculating the Gibbs energy barrier based on solution thermodynamics and the drive force from stress difference between α p and β phases. With the decrease of temperature, α p phase fraction varies little with deformation as a result of the counteraction between dynamic transformation of α p →β and strain-induced phase transformation of β→ α p . However, the deformation under the off-equilibrium condition can accelerate the precipitation kinetics of secondary alpha ( α s ) phase evidently. Moreover, a large amount of fine equiaxed α s phase can be formed by intragranular nucleation. Finally, it is found that, with the deformation at high temperature, the loss of Hall–Petch strengthening is principal source of flow softening. Meanwhile, the quantity of flow softening is less than that of the loss of Hall–Petch strengthening, which is associated with pronounced precipitation of α s phase. At the low temperature, flow softening by the loss of Hall–Petch strengthening is minor compared to that by α s laths rotation.

We used the habitat suitability index (HSI) model to determine the habitat suitability of为了深入了解海黍子生境,利用模型对山东俚岛海黍子生境进行适宜性分析,分别选取温度、盐度、水深、浊度、底质、无机氮浓度、磷酸盐浓度和距海藻床距离8种环境因子,通过层次分析法赋值因子权重,结合空间分析方法建立了海黍子HSI模型。利用该模型对山东俚岛近岸海域2018年春、秋两季的环境因子调查结果进行了海黍子生境分析。结果表明: 研究区域内的海黍子海藻床区域主要由极佳生境和适宜生境组成,春季和秋季的分布面积分别占14.2%和18.6%。海黍子生境层级分布随季节而变化,且不同季节的生境层级具有一定的空间重合性。温度和磷酸盐浓度的适宜性变化具有明显的季节性差异,是导致俚岛海黍子HSI季节变化的主要原因。海黍子HSI模型不仅可用于检测海黍子海藻床区域的生境层级分布,还能发现海黍子潜在的适宜生境区域。这为今后开展海黍子资源保护和人工增殖工作提供了科学参考。.