Structural changes in VT1-0 titanium induced by deformation during explosion welding

The hardening of VT1-0 titanium is studied during the formation of a multilayer material by explosion welding. The structural transformations in titanium plates are analyzed by metallographic and electron-microscopic methods. The mechanical properties of the welded multilayer titanium stacks are estimated using static and dynamic mechanical tests.     

Microstructural changes produced in a multifilamentary Nb-Ti composite by cold work and heat treatment

The microstructural changes produced by cold work and heat treatment of a full-scale filamentary Nb-Ti superconducting composite have been investigated using transmission electron microscopy. Full details of the processing conditions used are given, and both longitudinal and transverse sections of the microstructure have been examined. Heat treatments are found to give a complex precipitate morphology; the precipitates produced by heat treatments at 648 K (375 °C) were found to range from a thin boundary film 3 to 6 nm thick, through small approximately ellipsoidal precipitates (~5 x 10 nm), to larger (~50 to 500 nm) equiaxed precipitates. The larger precipitates could be identified as α-Ti. Cold drawing was found to refine the microstructure, but an even greater degree of refinement was observed when intermediate heat treatments were applied. The observations of this investigation show a strong interdependence between the cold-worked substructure and the precipitate morphology in these heat-treated and heavily cold-worked (ε ~ 5 to 9) composites.     

Morphologic changes in collagen fibers after 830 nm diode laser welding

BACKGROUND AND OBJECTIVE: The mechanism of laser tissue welding is elusive, but collagen transitions are somehow involved. Collagen fiber modifications observed after 830 nm diode laser welding are presented in this study. STUDY DESIGN/MATERIALS AND METHODS: A 830 nm diode laser assisted longitudinal aortorrhaphy was performed on 37 Wistar rats, with shots of 0.5 W in power, 8 sec in duration and 250 W/cm2 in irradiance. Energy utilized ranged from 400-550 J/ mm2 for 1 cm-length of anastomosis. After laser welding, histological modifications in collagen fibers were observed through optic, scanning electron, and electron microscopic examination. RESULTS: After laser welding, collagen fibers lost a proportion of birefringence. Under electron microscope, the different changes in collagen fibers were visualized being either fused, "roped," swollen, or dissolved, surrounded by normal ones situated in the same zone. CONCLUSION: These data suggest that diode laser heating denatured part of the collagenic fibers, and that these morphologic changes play an important role in laser welding.     

利用反应热处理制备纳米晶WC-10Co复合粉末

对反应热处理技术(即高能球磨+热处理)合成纳米晶WC-10Co复合粉末的工艺进行了研究。DTA分析结果表明:以W,Co粉和碳黑为原料的混合物经过一定的活化处理后,碳化钨可在572℃左右形成;通过改变反应热处理时间和温度,合成的纳米碳化钨晶粒尺寸在9～42nm之间变化。反应热处理技术是合成纳米晶WC-Co复合粉末的行之有效的方法。     

Structural changes in the surface layer of plasma coatings with ultrasonic treatment by steel balls

Conclusions Ultrasonic treatment with metal balls provides a reduction in the surface roughness of plasma coatings with a mcirohardness of 5630–7890 MPa by a factor of one and a half, and with a thickness of deposited layer less than 4·10^–4 m the time required in order to achieve the minimum roughness depends considerably on the magnitude of residual compressive stresses and the properties of the base.The shock effect of balls changes the size of mosaic blocks, dislocation density, and the magnitude of microstresses in the surface layer of a coating, and the treatment time required in order to achieve the maximum changes is reduced with a smaller deposited layer thickness.Ultrasonic treatment of plasma coatings provides formation at their surface layer of structures which improve the wear resistance of deposited coatings under fretting conditions by a factor of two to four.Translated from Poroshkovaya Metallurgiya, No. 2(350), pp. 23–28, February, 1992.     

Structural changes in bilayer membranes by multivalent ions

Formation of microlenses, a reduction in thickness, and a change in mechanical properties have been observed when Ca2+ or other multivalent ions are added to bathing solutions of Mueller-Rudin membranes of acidic phospholipids. The observations are interpreted as an extrusion of residual solvent from the hydrocarbon core of the bilayer due to changes in packing imposed by the reduction of electrostatic repulsion of the head groups.     

Structural changes in the tissues of white rats after capsaicin administration

Attitudes to health and illness may differ between rural and urban dwellers. Issues that may relate to the provision of health services to rural dwellers are raised for consideration. The response of urban dwellers to illness or disability has often been linked to discomfort caused by pain or cosmetic attractiveness, while for rural dwellers the response to illness or disability is often related to the degree to which the illness or disability affects productivity. Often the rural resident will postpone seeking medical or associated services until it is economically or socially convenient. The notion of exposing their private lives to strangers or acquaintances from the local based services or to undertake the journey to distant services where the cultural or behavioural differences could be misunderstood, may impact on rural dwellers' well-being. Health service providers in rural areas need to understand such differences and difficulties when offering services.     

TiAl合金建筑材料焊后热处理组织及性能研究

对建筑用TiAl合金电子束焊接接头进行了两种热处理试验研究,借助金相显微镜(OM)分析了接头不同区域的显微组织,并对焊接接头进行显微硬度测试,分析了两种热处理方式对建筑TiAl合金焊接接头组织及硬度带来的变化.研究表明,TiAl合金电子束焊接后焊缝组织主要为α2相,B相与O相.焊接接头局部热处理后接头硬度较高的区域有所...     

Changes in QOL in patients with brain tumors measured by mood changes during and after treatment

Patients with brain tumors are exposed to severe stress which may have an influence on their quality of life (QOL). To measure QOL in those patients, we measure their mood state during and after the treatments. MATERIALS: 16 patients who were admitted to our department for treatment of brain tumors, were included in the study. The tumors included 5 gliomas, 6 meningiomas and others. They were 7 males and 9 females, and age distributed from 19 to 74 years old. All patients presented more than 90% of the Karnofsky performance score (KPS) on discharge, so they were expected to return to their previous social life. METHOD: The self-answering tests were performed on admission (Pre), on discharge (Post 1), and at more than 5 months after the discharge (Post 2). The tests included an original questionnaire asking consent to admission and treatment, and concerning the feeling of disability to cope with conditions of living, Cornell Medical Index (CMI) which measured the neurosis, and Profile of mood state (POMS) which measured the 6 subscales of patients mood states including tension-anxiety (TA), depression (D), anger-hostility (AH), vigor (V), fatigue (F), and confusion (C). RESULTS: The questionnaire showed that the patients feel satisfied with having consented to the treatment. The feeling of disability to cope with living became stronger in Post 2 than in Pre. CMI showed a borderline of neurosis in three patients on admission, and in four patients in Post 2. Only the TA of POMS subscale improved significantly in Post 2. However, other subscales were unchanged. It is characteristic that all of the subscales of POMS showed less disturbance on discharge compared with that on admission, but, they returned to the Prelevel after they returned to social life. CONCLUSIONS: Patients with brain tumors have satisfactory consent to the treatment, however, they feel disability to cope with social life. On discharge, they showed a better mood state compared to that on admission, but the mood state turned for the worse again during the follow-up period. It is evident that patients with brain tumors are exposed to severe stress even after the completion of the treatment. The results necessitate our taking patients' mental health into consideration for our treatment protocol.     

The thermal fatigue behavior of the combustor alloys In 617 and HAYNES 230 before and after welding

The nickel-base alloys IN 617 and HAYNES 230 for welded high-temperature components have been subjected to thermal fatigue (TF) loading. In a series of TF tests in air, single wedge specimens were induction heated and compressed-air cooled at the leading edge for various temperature cycles between 200 °C and either 850 °C, 950 °C, or 1050 °C. The test rigs permitted simultaneous measurements of temperature and total strain along the edge of specimen during TF cycling. Both materials have been tested in conditions relevant for hot path components in the gas turbines, e.g., “as delivered,” “welded,” and “welded + notched”. Under identical temperature cycles and thermal gradients, HAYNES 230 showed a higher TF strength than IN 617 in the as-delivered condition. It is suggested that this advantage of HAYNES 230 is primarily related to its lower value of the relevant combination of properties of this alloy: coefficient of thermal expansion, thermal conductivity, elastic modulus, ultimate tensile strength, taken at maximal operating temperature. In addition, the advantage of the HAYNES 230 is described by a lower plastic strain, which is induced at the wedge region during TF loading. Moreover, microstructural details of crack initiation, crack propagation, and reactions with the gaseous environment play an important role. Both alloys investigated in the present work showed plastic deformation with a maximum in the central zone of the wedge tip. In this zone, slip bands and grain distortion occurred, whereas both ends of the wedge tip free of visible plastic deformation. The TF cycles led to multiple transgranular crack initiation and propagation. In welded specimens of IN 617 and HAYNES 230, cracks appeared first in the center of the weld. The susceptibility of welds to TF cracking depends considerably on the weld filler and the surface quality. It was shown for HAYNES 230 that a mismatched weld could reduce the TF life to less than 50 pct of non-welded specimens. The lower TF-fatigue strength of the welded specimens can be explained by the difficulty of the cast alloy in the welded zone to accommodate the repeated thermal shocks by plastic deformation. Notches introduced in the heat-affected zone (depth about 0.1 mm) reduced the TF life of both alloys by a factor as high as 4. The thermal fatigue strength of the welded material can almost reach the values of the base alloy provided the use of matching electrodes, post-weld heat treatment, and grinding off the weld beads is carefully executed.     

Serum mineral changes in dithizone-induced diabetes before and after insulin treatment

In this study, diabetes was induced by intravenous injection of dithizone. In dithizonised diabetic animals, the levels of serum zinc, iron, and potassium were found to be higher than normal, while those of serum calcium and sodium were lower. Copper and magnesium levels were unchanged. After treatment with insulin, most of these serum levels approached the normal, except for serum potassium and magnesium.     

Effects of mechanical and thermal treatment on the properties of a silver-cadmium oxide composite

Measurements have been made on the corrosion resistance, residual porosity, impact toughness, and structure of a silver-cadmium oxide composite caused by rolling and heat treatment of sintered powder blanks. The corrosion resistance has been examined for contacts composed of a rolled composite consisting of silver with 15% cadmium oxide and contacts of grade KMK A10m made from the same material by pressing and sintering.Materials Science Institute, National Academy of Sciences of Ukraine, Kiev. All-Union Electromechanics Research Institute, Istra. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 104–108, March–April, 1994.     

Structure and mechanical properties of a multilayer carbide-hardened niobium composite material fabricated by diffusion welding

The structure, the bending strength, and the fracture mechanism of an artificial niobium-based composite material, which is fabricated by high-pressure diffusion welding of multilayer stacks assembled from niobium foils with a two-sided carbon coating, are studied. The microstructure of the composite material is found to consist of alternating relatively plastic layers of the solid solution of carbon in niobium and hardening niobium carbide layers. The room-temperature proportional limit of the developed composite material is threefold that of the composite material fabricated from coating-free niobium foils using the proposed technology. The proportional limit of the developed composite material and the stress corresponding to the maximum load at 1100°C are 500 and 560 MPa, respectively. The developed material is considered as an alternative to Ni–Al superalloys.     

Body weight and body composition changes after treatment of hyperthyroidism

Body composition changes in nine adults with hyperthyroidism were determined with dual energy x-ray absorptiometry and computed tomography at diagnosis and after 3 and 12 months of euthyroidism achieved by surgery, antithyroid drugs, or treatment with radioiodine. Mean body weight was 67.6 kg at diagnosis and increased 2.7 kg (P=0.06) and 8.7 kg (P < 0.001) after 3 and 12 months of euthyroidism, respectively. Basal metabolic rate decreased from 2087 Cal/24 h at diagnosis to 1601 Cal/24 h at 12 months (P=0.001), whereas reported energy intake dropped from 3244 to 2436 Cal/24 h (P=0.01). According to dual energy x-ray absorptiometry, body fat was unchanged at 3 months, but increased by 5.3 kg (P < 0.0001) at 12 months. Fat-free mass increased 2.7 kg (P=0.003) at 3 months and 3.5 kg (P < 0.0001) at 12 months. Changes in bone mineral content and density did not reach significance. According to computed tomography, skeletal muscle plus skin areas increased by 11% (trunk) and 18% (thigh) at 3 months and by 17% (trunk) and 25% (thigh) at 12 months. There was no increase in sc adipose tissue (AT) at 3 months, but at 12 months this AT depot increased by 15% (thigh) and 33% (trunk). Intraperitoneal AT showed a borderline significant increase by 28% (P=0.08) at 3 months and by 40% (P=0.015) at 12 months. Areas of visceral organs and bone tissue of femur did not change significantly during the study. It is concluded that during early recovery from hyperthyroidism, priority is given to the replenishment of skeletal muscles and ip AT, whereas sc AT is increased at a later stage.     

Influence of heat treatment after welding on the microhardness of steel joints in marine platforms

Weld joints in fixed marine platforms must be highly reliable. Certain zones of the weld seam may be very hard and hence may act as stress concentrators. Therefore, in some cases, additional heat treatment is required after welding. The microhardness of the basic sections in the weld joint of microalloyed low-carbon streel sheet (thickness 60 mm) obtained by thermomechanical rolling is investigated. Two-coordinate measurements of the microhardness in the basic thermal-influence zones are described. The influence of postweld heat treatment on the microhardness of opposite walls of the weld joint is determined.