Martensite reorientation after thermal cycling in NiTiCu shape memory alloys studied by EBSD technique

The Ni25Ti50Cu25 shape memory alloy exhibits one-step martensitic transformation. Transformation occurs between the B2 parent phase and the B19 orthorhombic martensite. The course of the martensitic transformation was in situ studied in the alloy with use of electron backscatter diffraction. During heating, reverse martensitic transformation occurs from the B19 orthorhombic martensite to the B2 parent phase. On cooling, from the parent phase the B19 martensite is formed. Obtained results proved that the B19 martensitic plates forms the variants indexed as 1, 3, and 5. Thermal cycling does not change the crystallographic correlation between the parent phase and the martensite. However, after cycling, different rearrangement of the martensitic plates can be received. In consequence, characteristic temperatures of the martensitic transformation are shifted

Spark plasma sintering the spark-erosion powders of functional alloys

Various shape memory alloys (Ti-Ni-Hf, Ni-Al and Cu-Al-Ni) were elaborated by spark plasma sintering method from the micron, submicron and nano- sized particles prepared by spark-erosion method in cryogenic liquid from preliminary melted master alloys. These alloys are being developed as one of the alternatives for the intermediate temperature applications (100-900oC). Spark plasma sintering method is express method, which provides lower temperature and shorter holding time of sintering. It makes possible to sinter materials from the pre-alloyed powders and eliminate the intensive grains growth and precipitating processes influencing the mechanical and functional properties of functional materials. The effects of processing parameters on the martensitic transformation and microstructure of the sintered compacts were investigated using XRD and SEM study. Temperatures of sintering were chosen according to the assessed data of the decomposition, oxidation and others processes carrying out in material. Although the precipitating processes were usually not completely depressed, the intensive grain growth was also not found in most cases. Most of the microstructure peculiarities of as processed powder were inherited by the sintered material. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2079

The Role of Nano-sized Fraction on Spark Plasma Sintering the Pre-Alloyed Spark-Erosion Powders

Ti-Ni-Hf, Ni-Al and Cu-Al-Ni shape memory materials were produced by spark plasma sintering method from the micron and nano-sized particles prepared by spark-erosion method in cryogenic liquid from preliminary melted master alloys. The effects of spark plasma sintering processing parameters on the martensitic transformation and microstructure of the sintered compacts were investigated using XRD and SEM methods. Although precipitating processes were usually not completely depressed, the intensive grain growth was also not found in most cases. Most of the microstructure peculiarities of as processed powder were inherited by the sintered material. The contradictory role of the nano-sized fraction of powders is discussed: in most case this fraction promotes the rapid sintering but also the oxidation proceses in sintered compacts. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2489

Thermal and magnetic propertiesof selected Fe-based metallic glasses

Purpose: The work presents a thermal stability characterization and soft magnetic properties analysis of selected Fe-based metallic glasses. Design/methodology/approach: The studies were performed on ribbons prepared by the planar flow casting technique, which is a method of continuous casting of the liquid alloy on a surface of turning copper based wheel. The methods of X-ray diffraction were used for the qualitative phase analysis. The thermal properties associated with crystallization temperature of the glassy alloys were measured using the differential thermal analysis. The magnetic properties were determined by the Maxwell-Wien bridge, fluxometer and VSM methods. Findings: The studied Fe72B20Si4B4 and Fe36Co36B19Si5Nb4 metallic glasses in as-cast state were fully amorphous. The Curie temperature (Tc) for Fe72B20Si4B4 alloy has a value of 582 K and Fe36Co36B19Si5Nb4 has higher Tc, which has a value of 605 K. The obtained magnetic properties allow to classify the studied amorphous alloys in as-cast state as soft magnetic materials. The coercive field of tested alloys has a value about 8 A/m. The maximum magnetic permeability of Fe72B20Si4B4 alloy (!max = 21500) is much higher than Fe36Co36B19Si5Nb4 metallic glasses (!max = 3200). Similarly, saturation magnetization of Fe72B20Si4B4 alloy (Bs = 1.04 T) is higher than Fe36Co36B19Si5Nb4 (Bs = 0.99 T) amorphous alloy. Practical implications: The studied glassy alloys are suitable materials for many electrical application in different elements of magnetic circuits and for manufacturing of sensors and precise current transformers. Originality/value: The obtained results confirm the utility of applied investigation methods in the thermal and magnetic properties analysis of examined amorphous alloys

Mechanical behavior of Zr-based bulk metallic glasses

Bulk metallic glasses have a very high corrosion resistance and mechanical strength. Bulk metallic glasses show elastic-perfectly plastic behavior with an extended region of elastic strain (≈ 2%). But at room temperature their macroscopic plasticity is weak even though a local plastic strain is observed in shear bands. A relaxation analysis allowed studying micro-mechanisms of plastic deformation and estimating the apparent activation volume (≈ 2000 ³).Высокопрочные стекла на основе металлов имеют очень высокие характеристики коррозионной устойчивости и механической проч­ности. Их деформирование является абсолютно упругопластическим с протяженным участком упругости (≈ 2%). Однако при комнатной температуре их макропластичность проявляется слабо, несмотря на наличие локальных пластических деформаций в поло­сах скольжения. Анализ релаксации напряжений позволил исследовать микромеханиз­мы пластического деформирования и оценить значение объема активации (≈ 2000 ³)

Mechanical Testing of the Shape-Memory Materials Synthesized by a Plasma-Spark Method

Испытания на сжатие были выполнены при комнатной температуре для образцов сплавов Ni49,0—Mn28,5—Ga22,5 (ат.%) и Ni63—Al37 (ат.%), как для выплавленных, так и полученных плазменно-искровым методом (ПИМ). Для обеих систем пластичность ПИМ-образцов возрастает более чем на порядок по сравнению с исходными. Прочность на сжатие сплава Ni—Mn—Ga увеличивается от 180—240 МПа для выплавленных образцов до 510—815 МПа для ПИМ-образцов в зависимости от режимов обработки, для сплава Ni—Al – от 760 до 1310 МПа. Напряжение разрушения образцов Ni—Mn—Ga увеличивается от 185—215 до 1170 МПа, а для образцов Ni—Al – от 790 до 1870 МПа. Спечённые образцы обеих систем имеют композитную структуру, образованную из металлических частиц микронных размеров, скреплённых связующей фазой, состоящей из Ni₃Al и Al₂O₃ для сплава Ni—Al и из MnO с небольшим количеством Ni₃Ga для сплава Ni—Mn—Ga. Предполагается, что эта фаза укрепляет границы зёрен. Это вместе с уменьшением размера зерна, а также многосвязной морфологией образцов Ni—Mn—Ga, консолидированных из полых частиц, и наличием пластической γ′-фазы в частицах Ni—Al улучшает механические свойства сплавов, полученных плазменно-искровым методом.Випробування на стиснення було виконано при кімнатній температурі для зразків стопів Ni49,0—Mn28,5—Ga22,5 (ат.%) та Ni63—Al37 (ат.%), як щойно витоплених, так і одержаних плазмово-іскровою методою (ПІМ). Для обох систем пластичність ПІМ-зразків зростає більш ніж на порядок порівняно із вихідними. Міцність на стиск стопу Ni—Mn—Ga збільшується від 180—240 МПа для щойно витоплених зразків до 510—815 МПа для ПІМ-зразків, залежно від режимів оброблення; для стопу Ni—Al – від 760 до 1310 МПа. Напруження руйнування зразків Ni—Mn—Ga збільшується від 185—215 до 1170 МПа, а для зразків Ni—Al – від 790 до 1870 МПа. Спечені зразки обох систем мають композитну структуру, утворену з металевих частинок мікронних розмірів, пов’язаних сполучною фазою, що складається з Ni₃Al і Al₂O₃ для стопу Ni—Al та з MnO з невеликою кількістю Ni₃Ga для стопу Ni—Mn—Ga. Передбачається, що ця фаза зміцнює межі зерен. Це разом із зменшенням розміру зерна, а також багатозв’язною морфологією зразків Ni—Mn-Ga, консолідованих із порожнистих частинок, та наявністю пластичної γ′-фази в частинках Ni—Al покращує механічні властивості стопів, одержаних плазмово-іскровою методою.Compression tests are carried out at room temperature with the as-cast and spark-plasma sintered (SPS) specimens of Ni49.0—Mn28.5—Ga22.5 (at.%) and Ni63—Al37 (at.%) alloys. For both systems, ductility of the SPS compacts increases more than by one order of magnitude. Compressive strength of Ni—Mn—Ga alloy increases from 180—240 MPa for induction melted specimens to 510—815 MPa for spark-plasma sintered specimens, depending on the regimes of processing, and for Ni—Al alloy, from 760 to 1310 MPa. Fracture stress of Ni—Mn—Ga and Ni—Al specimens raise from 185—215 to 1170 MPa and from 790 to 1870 MPa, respectively. The SEM and XRD investigations reveal that sintered samples of both systems have a composite structure, which contains the micron-size metallic particles bound by the binder phase. This phase consists of Ni₃Al and Al₂O₃ phases in case of Ni—Al alloy and consists of MnO with apparently small amount of Ni₃Ga phase in case of Ni—Mn—Ga alloy. As assumed, this phase strengthens the grain boundaries. This one, in conjunction with reduction of the grain size, the manifold morphology of the Ni—Mn—Ga specimens consolidated from the hollow particles, the presence of extra ductile γ′-phase in Ni—Al particles, provides the enhancing mechanical properties of alloys fabricated by means of the SPS method

Microstructure Investigation of the Spark Plasma Sintered Cu—Al—Ni Shape Memory Material

Исследована микроструктура компактов Cu—13,0Al—3,9Ni—0,4Ti—0,2Cr масс.%, спечённых плазменно-искровым методом из электроэрозионных порошков, изготовленных из мастер-сплава в жидком аргоне.Досліджено мікроструктуру компактів Cu—13,0Al—3,9Ni—0,4Ti—0,2Cr ваг.% спечених плазмово-іскровим методом із електроерозійних порошків, виготовлених із мастер-стопу в рідкому арґоні.The microstructure of Cu—13.0Al—3.9Ni—0.4Ti—0.2Cr wt.% compacts sintered by spark plasma method from powders prepared by spark-erosion method in liquid argon from master alloy is investigated

Association between inflammation, lipopolysaccharide binding protein, and gut microbiota composition in a New Hampshire Bhutanese refugee population with a high burden of type 2 diabetes

IntroductionSouth Asian refugees experience a high risk of obesity and diabetes yet are often underrepresented in studies on chronic diseases and their risk factors. The gut microbiota and gut permeability, as assessed through circulating lipopolysaccharide binding protein (LBP), may underlie the link between chronic inflammation and type 2 diabetes (T2D). The composition of the gut microbiota varies according to multiple factors including demographics, migration, and dietary patterns, particularly fiber intake. However, there is no evidence on the composition of the gut microbiota and its relationship with metabolic health in refugee populations, including those migrating to the United States from Bhutan. The objective of this study was to examine glycemic status in relation to LBP, systemic inflammation fiber intake, and gut microbiota composition in Bhutanese refugee adults residing in New Hampshire (n = 50).MethodsThis cross-sectional study included a convenience sample of Bhutanese refugee adults (N = 50) in NH. Established bioinformatics pipelines for metagenomic analysis were used to determine relative genus abundance, species richness, and alpha diversity measures from shallow shotgun sequences. The relationships between inflammatory markers, gut microbiota composition, dietary fiber, and glycemic status were analyzed.ResultsWe identified a substantial chronic disease burden in this study population, and observed a correlation between glycemic status, LBP, and inflammation, and a correlation between glycemic status and gut microbiome alpha diversity. Further, we identified a significant correlation between proinflammatory taxa and inflammatory cytokines. SCFA-producing taxa were found to be inversely correlated with age.ConclusionTo date, this is the most comprehensive examination of metabolic health and the gut microbiome in a Bhutanese refugee population in NH. The findings highlight areas for future investigations of inflammation and glycemic impairment, in addition to informing potential interventions targeting this vulnerable population

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570