Ultrafine grain evolution in a Cu-Cr-Zr alloy during warm multidirectional forging

The microstructure evolution and the deformation behavior of a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging at a temperature of 673 K under a strain rate of about 10-³ s-¹ were studied. Following a rapid increase in the flow stress during straining to about 1, the strain hardening gradually decreases, leading to a steady-state flow behavior at total strain above 2. The multidirectional forging led to the development of ultrafine grained microstructures with mean grain sizes of 0.9 μm and 0.64 μm in the solution treated and aged samples, respectively. The presence of second phase precipitates promoted the grain refinement. After processing to a total strain of 4, the fractions of ultrafine grains (D < 2 μm) comprised 0.36 and 0.59 in the solution treated and aged samples, respectivel

Método de obtención de la fase beta estable de un metal puro de transición del grupo IV del sistema periódico y producto obtenible por dicho método

Método de obtención de la fase beta estable de un metal puro de transición del grupo IV del sistema periódico y producto obtenible por dicho método. Se describe un nuevo método para la fabricación controlada de la fase beta de los metales de transición del grupo IV del sistema periódico que es estable en condiciones ambiente (1 atmósfera y 22ºC). El procedimiento comprende una primera etapa de aplicación, sobre una muestra (2) elaborada de la fase alfa del metal de transición considerado, de una presión de compresión de un valor mínimo de entre 1 y 3 GPa, seguida de una segunda etapa de aplicación, manteniendo dicha presión, de una deformación de cizalladura, de valor mínimo no superior a 39.2. El procedimiento descrito permite obtener fase beta estable de metales de transición del grupo IV empleando presiones y cizalladuras de valores sensiblemente inferiores que en el caso de obtención de dicha fase beta estable por medios que no implican aplicación simultánea de presión y cizalladura.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Instituto Madrileño de Estudios AvanzadosA1 Solicitud de patente con informe sobre el estado de la técnic

In-situ nanocomposite in friction stir welding of 6061-T6 aluminum alloy to AZ31 magnesium alloy

Prior to friction stir welding (FSW), silicon carbide (SiC) nanopowders were placed inside the groove on the adjacent side of magnesium sheet. In order to make a good distribution of these nanoparticles, first, friction stir processing (FSP) with a pinless tool was conducted on this side. Second, using a frustum pin tool, a combination of two travel speeds (25 and 35¿mm/min) and three rotation speeds (550, 600 and 650¿rpm) were employed to obtain the optimal conditions for FSW of AZ31 magnesium alloy to 6061 aluminum alloy. The joint fabricated at 35¿mm/min and 650¿rpm, exhibited improvement of 28% in tensile strength and enhancement about three times in elongation, compared with the joint without nanoparticles. SiC nanoparticles had an effective role on the grain refining of the stirred zone and improving the microstructural characteristics of the banded structure zone. Due to the decreased grain size and the presence of ceramic nanoparticles (SiC) with high value of hardness, the hardness level of the reinforced samples was greater than that of the non-reinforced samples. Fracture of the non-reinforced sample was completely brittle, while in the reinforced samples, fracture features changed to the ductile mode.Peer ReviewedPostprint (author's final draft

Softening and hardening of ECAP nickel under ultrasonic treatment

Commercially pure nickel was processed by equal channel angular pressing (ECAP) through route Bc for 12 passes to obtain an ultrafine grained (UFG) microstructure and further subjected to an ultrasonic treatment (UST) which introduced a maximum amplitude equivalent to anormal stresses of 100 MPa in a steady state regime. It was observed that the microstructure of UFG Ni can be differently altered depending on the position in the sample, i.e. on the amplitude of the ultrasonic wave. The microstructural analysis demonstrated a lower dislocation density (due to the activation of recovery) at the cross section of the specimen subjected to UST at an amplitude equal to 0.8 of the maximum one, plus enhanced hardening in the cross section at the maximum amplitude.Preprin

Grain refinement kinetics and strengthening mechanisms in Cu-0.3Cr-0.5Zr alloy subjected to intense plastic deformation

The ultrafine-grained microstructures, mechanical properties and electrical conductivity of a Cu-0.3%Cr-0.5%Zr alloy subjected to equal channel angular pressing (ECAP) at a temperature of 400°C to a total strain of 1, 2, and 4 were investigated. The ultrafine-grained microstructure resulting from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process is considered as a type of continuous dynamic recrystallizatio

Fundamentals of interface phenomena in advanced bulk nanoscale materials

The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materials processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by TEM, high-resolution x-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studied. Also enhanced grain boundary diffusivity is addressed. Structure recovery and dislocation emission from grain boundaries in nanocrystalline materials have been investigated by analytical methods and modeling

Особенности течения инфекционного артрита у пациента с гипогаммаглобулинемией

Hypogammaglobulinemia is a condition caused by low levels of immunoglobulins in the blood serum. It can be a manifestation of primary immunodeficiency, characterized by a violation of the production of immunoglobulins, in particular common variable immunodeficiency (CVID). A typical clinical sign of CVID is various severe infections, among which infectious arthritis is not uncommon. At the same time, the clinical picture of infections can differ significantly from that in individuals with a normal immune response, including the spectrum of infectious arthritis pathogens.The article describes a clinical case of an unusual course of infectious arthritis in a patient with newly diagnosed hypogammaglobulinemia. The peculiar features of the case were a long (more than 1.5 years) course of the disease, without the development of septic complications, no increase in ESR and CRP, recurrence of arthritis after a 2-month course of antibiotic therapy, and the presence of generalized edema. The causes and diagnosis, features of infectious complications, including infectious arthritis, and probable causes of edematous syndrome in CVID are discussed.Гипогаммаглобулинемия – состояние, обусловленное низким уровнем иммуноглобулинов в сыворотке крови. Она может быть проявлением первичного иммунодефицита, характеризующегося нарушением продукции иммуноглобулинов, в частности общей вариабельной иммунной недостаточностью (ОВИН). Типичным клиническим признаком ОВИН являются различные инфекции тяжелого течения, среди которых нередки и инфекционные артриты. При этом клиническая картина инфекций может значительно отличаться от таковой у лиц с нормальным иммунным ответом, в том числе спектром возбудителей инфекционного артрита. В статье описано клиническое наблюдение необычного течения инфекционного артрита у пациента с впервые выявленной гипогаммаглобулинемией. Особенностями случая были длительное (более 1,5 лет) течение заболевания без развития септических осложнений, отсутствие повышения СОЭ и СРБ, рецидив артрита после 2-месячного курса антибактериальной терапии, а также наличие генерализованных отеков. Обсуждаются причины и диагностика, особенности инфекционных осложнений, в том числе инфекционных артритов, и вероятные причины отечного синдрома при ОВИН