Effects of Nb Content on Yield Strength of NiTiNb Alloys in Martensite State

AbstractTwo near single-phase NiTiNb alloys—Ni50Ti48Nb2 and Ni49.5Ti46.5Nb4—are prepared and studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC) and tensile tests in order to unearth the effects of Nb-atom solid solution in NiTi phase on the yield strength induced by self-accommodation of martensite variants. The results show that the yield strength of near single-phase NiTiNb alloys varies inversely with the amount of Nb-atoms solid-dissolved in NiTi phase. From the results out of the prior and current studies, it can be surmised that the effects of Nb content on the yield strength of NiTiNb alloys in martensite state depend on the coaction. Nb solid solution weakening mechanism and β-Nb phase composite strengthening mechanism. This inference might be a satisfactory explanation to the fact that the yield strength of (NiTi)50–0.5xNbx alloys in martensite state begins with decline and then rises when the Nb content increases

Phase Equilibria in Nb-Si-Mo Ternary Alloys at 1 273 K and 2 073 K

AbstractPhase equilibrium in Nb-Si-Mo ternary alloys (<37.5 at.% Si) at 1 273 K and 2 073 K is investigated by using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The partial isothermal section at 1 273 K, which contains four single-phase regions, five two-phase regions and two three-phase regions, is basically the same as that at 1 973 K. However, when the temperature increases to 2 073 K, the three-phase region of Nbss+α-(Nb(Mo))5Si3+β-(Nb, Mo)5Si3 obviously moves towards the Nb-rich corner. This suggests that Nb-Si-Mo ternary alloys remain stable at least up to 1 973 K

α′ Type Ti–Nb–Zr alloys with ultra-low Young's modulus and high strength

Abstractα′ phase based Ti–Nb–Zr alloys with low Young's modulus and high strength were prepared, and their microstructure and mechanical properties were characterized. It was revealed that the lattice expansion by Nb and Zr addition as well as the presence of a few of α″ martensite might be responsible for the low modulus achieved. Ti–15Nb–9Zr alloy, with ultralow modulus of 39GPa and high strength of 850MPa, could be a potential candidate for biomedical applications

Incorporating inflammatory biomarkers into a prognostic risk score in patients with non-ischemic heart failure: a machine learning approach

ObjectivesInflammation is involved in the mechanisms of non-ischemic heart failure (NIHF). We aimed to investigate the prognostic value of 21 inflammatory biomarkers and construct a biomarker risk score to improve risk prediction for patients with NIHF.MethodsPatients diagnosed with NIHF without infection during hospitalization were included. The primary outcome was defined as all-cause mortality and heart transplantations. We used elastic net Cox regression with cross-validation to select inflammatory biomarkers and construct the best biomarker risk score model. Discrimination, calibration, and reclassification were evaluated to assess the predictive value of the biomarker risk score.ResultsOf 1,250 patients included (median age, 53 years, 31.9% women), 436 patients (34.9%) experienced the primary outcome during a median of 2.8 years of follow-up. The final biomarker risk score included high-sensitivity C-reactive protein-to-albumin ratio (CAR) and red blood cell distribution width-standard deviation (RDW-SD), both of which were 100% selected in 1,000 times cross-validation folds. Incorporating the biomarker risk score into the best basic model improved the discrimination (ΔC-index = 0.012, 95% CI 0.003–0.018) and reclassification (IDI, 2.3%, 95% CI 0.7%–4.9%; NRI, 17.3% 95% CI 6.4%–32.3%) in risk identification. In the cross-validation sets, the mean time-dependent AUC ranged from 0.670 to 0.724 for the biomarker risk score and 0.705 to 0.804 for the basic model with a biomarker risk score, from 1 to 8 years. In multivariable Cox regression, the biomarker risk score was independently associated with the outcome in patients with NIHF (HR 1.76, 95% CI 1.49–2.08, p &lt; 0.001, per 1 score increase).ConclusionsAn inflammatory biomarker-derived risk score significantly improved prognosis prediction and risk stratification, providing potential individualized therapeutic targets for NIHF patients

Applying CS and WSN methods for improving efficiency of frozen and chilled aquatic products monitoring system in cold chain logistics

Wireless Sensor Network (WSN) is applied widely in food cold chain logistics. However, traditional monitoring systems require significant real-time sensor data transmission which will result in heavy data traffic and communication systems overloading, and thus reduce the data collection and transmission efficiency. This research aims to develop a temperature Monitoring System for Frozen and Chilled Aquatic Products (MS-FCAP) based on WSN integrated with Compressed Sending (CS) to improve the efficiency of MS-FCAP. Through understanding the temperature and related information requirements of frozen and chilled aquatic products cold chain logistics, this paper illustrates the design of the CS model which consists of sparse sampling and data reconstruction, and shelf-life prediction. The system was implemented and evaluated in cold chain logistics between Hainan and Beijing in China. The evaluation result suggests that MS-FCAP has a high accuracy in reconstructing temperature data under variable temperature condition as well as under constant temperature condition. The result shows that MS-FCAP is capable of recovering the sampled sensor data accurately and efficiently, reflecting the real-time temperature change in the refrigerated truck during cold chain logistics, and providing effective decision support traceability for quality and safety assurance of frozen and chilled aquatic products.Agro-scientific Researc

Bulk metastable cobalt in fcc crystal structure

Bulk metastable pure cobalt was fabricated by a simple sintering route with micrometer-sized Co particles as raw materials. The as-prepared bulk Co is composed of dominant metastable face-centered cubic (fcc) phase and a trace of hexagonal close-packed (hcp) phase at room temperature. The crystal structures and magnetic properties of the metastable bulk are very sensitive to external stresses. Obvious fcc-to-hcp phase transformation occurred under tensile loading, which was accompanied by significant increase of the coercivity and remanence. It is believed that the interface energy plays a key role in hindering the fcc-to-hcp allotropic transition, leading to the existence of metastable bulk Co with the higherature fcc structure at room temperature. © 2013 Elsevier B.V. All rights reserved.This work was supported by the National Natural Science Foundation of China (Grant No. 51271010) and the National Basic Research Program of China (Grant No. 2012CB619403).Peer Reviewe

Cure Cycle Optimization of Rapidly Cured Out-Of-Autoclave Composites

Out-of-autoclave prepreg typically needs a long cure cycle to guarantee good properties as the result of low processing pressure applied. It is essential to reduce the manufacturing time, achieve real cost reduction, and take full advantage of out-of-autoclave process. The focus of this paper is to reduce the cure cycle time and production cost while maintaining high laminate quality. A rapidly cured out-of-autoclave resin and relative prepreg were independently developed. To determine a suitable rapid cure procedure for the developed prepreg, the effect of heating rate, initial cure temperature, dwelling time, and post-cure time on the final laminate quality were evaluated and the factors were then optimized. As a result, a rapid cure procedure was determined. The results showed that the resin infiltration could be completed at the end of the initial cure stage and no obvious void could be seen in the laminate at this time. The laminate could achieve good internal quality using the optimized cure procedure. The mechanical test results showed that the laminates had a fiber volume fraction of 59–60% with a final glass transition temperature of 205 °C and excellent mechanical strength especially the flexural properties

Nano-hardness, wear resistance and pseudoelasticity of hafnium implanted NiTi shape memory alloy

NiTi shape memory alloy was modified by Hf ion implantation to improve its wear resistance and surface integrity against deformation. The Auger electron spectroscopy and x-ray photoelectron spectroscopy results indicated that the oxide thickness of NiTi alloy was increased by the formation of TiO2/HfO2 nanofilm on the surface. The nano-hardness measured by nano-indentation was decreased even at the depth larger than the maximum reach of the implanted Hf ion. The lower coefficient of friction with much longer fretting time indicated the remarkable improvement of wear resistance of Hf implanted NiTi, especially for the sample with a moderate incident dose. The formation of TiO2/HfO2 nanofilm with larger thickness and decrease of the nano-hardness played important roles in the improvement of wear resistance. Moreover, Hf implanted NiTi exhibited larger pseudoelastic recovery strain and retained better surface integrity even after being strained to 10% as demonstrated by in situ scanning electron microscope observation

Microstructural evolution and mechanical behavior of metastable β-type Ti–30Nb–1Mo–4Sn alloy with low modulus and high strength

A metastable β-type Ti–30Nb–1Mo–4Sn alloy with ultralow elastic modulus and high strength was fabricated. Under the solution treatment state, the Ti–30Nb–1Mo–4Sn alloy possesses low yield strength of about 130 MPa owing to the presence of the coarse α′′ martensitic laths. Upon a cold rolling and annealing process, the martensitic transformation from β to α′′ is significantly retarded due to the inhibitory effect of grain boundaries and dislocations. As a result, the metastable β phase with low total amount of β-stabilizers is retained to room temperature, giving rise to a low modulus of 45 GPa. Meanwhile, nano-sized α precipitates and dislocation tangles play a key role in strengthening the Ti–30Nb–1Mo–4Sn alloy, resulting in a high tensile strength of ~1000 MPa. With low elastic modulus and high strength, the metastable β-type Ti–30Nb–1Mo–4Sn alloy could be a potential candidate for biomedical materials

A β-type TiNbZr alloy with low modulus and high strength for biomedical applications

The effect of thermo-mechanical treatment on the mechanical properties of a novel β-type Ti–36Nb–5Zr (wt%) alloy has been investigated. The solution treated alloy consists of β and α″ phases and exhibits a two-stage yielding with a low yield stress (around 100 MPa). After cold rolling at a reduction of 87.5% and subsequent annealing treatment at 698 K for 25 min, a fine microstructure with nanosized α precipitates distributed in small β grains as well as high density of dislocations was obtained to achieve a yield strength of 720 MPa and a ultimate tensile strength of 860 MPa. In spite of the formation of α precipitates, the β-stabilizers are not enriched in the parent β matrix due to the short duration and low temperature of the thermal treatment, resulting in a low chemical stability of β phase. The low stability of β phase and the small volume fraction of α precipitates produce a low Young׳s modulus of 48 GPa. Such an excellent combination of low elastic modulus and high strength in mechanical properties indicates great potential for biomedical applications