Brazing of titanium to steel with different filler metals: analysis and comparison

Evaluations of vacuum brazed commercially pure titanium and low-carbon steel joints using one copper-based alloy (Cu–12Mn–2Ni) and two silver-based braze alloys (Ag–34Cu–2Ti, Ag–27.25Cu–12.5In–1.25Ti) have been studied. Both the interfacial microstructures and mechanical properties of brazed joints were investigated to evaluate the joint quality. The optical and scanning electron microscopic results showed that all the filler metals interact metallurgically with steel and titanium, forming different kinds of intermetallic compounds (IMC) such as CuTi, Cu2Ti, Cu4Ti3, and FeTi. The presence of IMC (interfacial reaction layers) at the interfacial regions strongly affects the shear strength of the joints. Furthermore, it was found that the shear strength of brazed joints and the fracture path strongly depend on the thickness of the IMC. The maximum shear strength of the joints was 113 MPa for the specimen brazed at 750 °C using an Ag–27.25Cu–12.5In–1.25Ti filler alloy.     

Frequency analysis of human primitive haematopoietic stem cell subsets using a cobblestone area forming cell assay

Stroma-dependent long-term bone marrow cultures (LTBMC) assay the ability of primitive haematopoietic stem cells (HSC) for long-term production of clonable progenitors. We have developed a limiting dilution type LTBMC assay allowing frequency analysis of transiently repopulating HSC and long-term culture initiating cells (LTC-IC) without the necessity to replate large numbers of wells. Normal or 5-FU-treated Ficoll bone marrow cells (BMC), or BMCs sorted on CD34 or HLA-DR expression, or Rh123 retention, (input range 40-70,000 CFU-GM/BFU-E/10(5) cells) were plated at limiting dilution on unirradiated adherent layers formed by a novel murine preadipose cell line (FBMD-1). The percentage of wells with at least one phase-dark haematopoietic clone (cobblestone area, CA) beneath the stromal layer was weekly determined for at least 8 weeks, and CA-forming cell (CAFC) frequencies were calculated using Poisson statistics. Parallel LTBMCs of the same samples were weekly assessed for supernate CFU-GM/BFU-E production. Weekly addition of rhIL-3 with rhG-CSF supported a high average clonogenic output per CA and dramatically increased CA size, but did not significantly alter the apparent CAFC frequency. The generation of CFU-GM per CA was constant over a period of 6 weeks with weekly means of eight normal BM samples, ranging between 5-16. At week 6 the mean CAFC frequency was 29 (1 SEM, 8.8)/10(5). Early appearing CAFC were highly sensitive to 5-FU, and were contained over the full Rh123 and HLA-DR fluorescence profile of CD34pos cells, whereas CAFC week 5-8 were predominantly contained in the CD34pos Rh123dull HLA-DRlow fraction in agreement with previously reported LTC-IC characteristics. In conclusion, the CAFC assay enumerates LTC-IC using a direct visual endpoint and allows study of LTC-IC heterogeneity with respect to progenitor cell generation per stem cell clone in various haematologic diseases.     

Sensory versus cognitive components in harmonic priming.

This study investigated the strength of sensory and cognitive components involved in musical priming. In Experiment 1, the harmonic function of the target chord and the number of pitch classes shared by the prime sequence and the target chord were manipulated. In Experiment 2, the temporal course of sensory and cognitive priming was investigated. For both musician and nonmusician listeners, cognitive priming systematically overruled sensory priming even at fast and very fast tempi (300 ms and 150 ms per chord). Cognitive priming continued to challenge sensory priming processes at extremely fast tempo (75 ms per chord) but only for participants who began the experimental session with slower tempi. This outcome suggests that the cognitive component is a fast-acting component that competes with sensory priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

GB virus C/hepatitis G virus infection: a favorable prognostic factor in human immunodeficiency virus-infected patients?

Lung disease is a rare complication of inflammatory bowel disease (IBD). Herein is a series of seven IBD patients who developed new, persistent and unexplained symptoms of respiratory disease, particularly chronic productive cough. Using a CT scan of the chest, a diagnosis of bronchiectasis was made in five patients, while the diagnosis of chronic bronchitis was made in two patients. Factors, other than IBD, that could account for pulmonary disease in these patients were absent. Several important clinical patterns for IBD-associated large airway disease were uncovered and are reviewed in light of earlier case reports in the medical literature. A discussion regarding the possible pathogenesis of IBD-associated airway disease follows.     

Verschleißfeste Beschichtungen von Aluminium‐Stahl‐Hybridstrukturen mittels thermischer Spritztechnik

Spraying of wear‐resistant coatings of aluminium‐steel‐hybrid‐structures By means of high velocity oxy fuel flame spraying of aluminium‐hybrid‐structures consisting of a Al Zn 5,5 Mg Cu 1,5 (ENAW7075) and a NiCrBSi‐coating as well as a Cr₃C₂ 25NiCr‐ coating are manufactured. The hybrid composite structures are analysed and compared with each other regarding to hardness, surface roughness, wear‐resistance and coating density.     

Influence of PVD-coating technology and pretreatments on residual stresses for sheet-bulk metal forming tools

Residual stresses in the substrate material are significantly influencing the performance of PVD-coated parts and tools which are exposed to high forces. Especially for forming operations, such as sheet-bulk metal forming, during which normal contact pressures of 1.4 GPa can occur, the reduction of friction and, at the same time, the wear protection by means of thin Cr-based coatings are essential. To ensure a long service life of forming tool and tool coating, each step of the substrate pre-treatment, as well as the magnetron-sputtering process, has to be coordinated and compatible. Therefore, polished as well as nitrided samples consisting of high-speed steel (AISI M3:2) are exposed to a sequence of plasma-based pre-treatments prior to depositing a CrAlN coating. Hardness and Young’s modulus of the substrate and the coating are analysed by means of nanoindentation. To determine the adhesion between coating and substrate, scratch tests are conducted and analysed using a scanning electron microscope. For each step, the residual stresses are determined using sin²ψ measurements, which are correlated to the mechanical properties. A plasma-nitriding process before the CrAlN coating induces high compressive residual stresses into the sample subsurface and at the same time increases the hardness of the surface. This results in higher critical loads during the scratch tests and therefore a better adhesion of the coating on the substrate.     

Wear Analysis of Thermal Spray Coatings on 3D Surfaces

Even though the application of thermal spray coatings on complex geometries gained a greater interest in the last decade, the effect of different geometrical features on the wear behavior is still ill-defined. In this study, the wear resistance of FTC-FeCSiMn coated 3D surfaces was investigated. The wear test was carried out by means of two innovative testing procedures. The first test is a Pin-on-Tubes test where the rotating motion is realized by a lathe chuck. The specimens in the second test were fixed on the table and a robot arm operated the pin. This wear test was applied on specimens with concave or convex surfaces. The residual stresses, which were determined by means of an incremental hole-drilling method, show a dependency on the substrate geometry. The obtained stresses were put in relation to the different radii. After the wear test, a 3D-profilometer determined the wear volume and the sections of the coatings were characterized by a scanning electron microscope. The results indicate that the wear resistance is strongly influenced by the geometry of the substrate.     

Empirical tight binding parameters for GaAs and MgO with explicit basis through DFT mapping

The Empirical Tight Binding (ETB) method is widely used in atomistic device simulations. The reliability of such simulations depends very strongly on the choice of basis sets and the ETB parameters. The traditional way of obtaining the ETB parameters is by fitting to experiment data, or critical theoretical bandedges and symmetries rather than a foundational mapping. A further shortcoming of traditional ETB is the lack of an explicit basis. In this work, a DFT mapping process which constructs TB parameters and explicit basis from DFT calculations is developed. The method is applied to two materials: GaAs and MgO. Compared with the existing TB parameters, the GaAs parameters by DFT mapping show better agreement with the DFT results in bulk band structure calculations and lead to different indirect valleys when applied to nanowire calculations. The MgO TB parameters and TB basis functions are also obtained through the DFT mapping process.