The segregation of iron in tungsten

Abstract

Segregation and solution of iron is followed up on a commercial WFe dilute alloy by measuring electrical resistivity, thermopower and — on the fracture surface — AES. The thermopower measures practically only the solute iron concentration in this alloy. At the same time the excess electrical resistivity is sensitive mostly to the concentration of grain boundaries and the AES measures the iron accumulated on the surface of the grain boundaries. According to these measurements grain boundary segregation occurs at temperatures where the bulk diffusion is negligible yet. So this segregation can be explained only by moving grain boundaries, which “sweep over” the crystallites, accumulating the iron atoms. It turned out that only a part of the iron segregated onto the grain boundaries, the larger part segregated onto the second phases, although their total surface is about ten times less. Supposing a state close to the equilibrium, the heats of segregation is estimated to be 50 and 100 to 120 kJ/mol for segregation to grain boundaries and to second phases, respectively.

Competitive growth texture of pulsed laser deposited vanadium dioxide nanostructures on a glass substrate

“…The observed variation of the surface morphology of the VO 2 nanostructures with cooling rate as reported in Fig. 4 may be due to the nucleation of the glass substrate which happens around 575 o C and followed by the process of crystallization of the VO 2 which follows the so called active fundamental structure forming phenomena well known in materials science and solid state physics (nucleation, crystal growth, grains growth) [50][51][52][53][54]. It is observed that the grains growth and the preferential texturation (crystal growth) are going to the opposite direction when increasing the cooling rate; this is supported by Figs.…”

“…By taking into account the structure evolution of real polycrystalline thin films [50][51][52][53][54] and that of the effects of the deposition parameter on the structure and on the appearance of peculiar structural features lead to the conclusion that the comprehensive description of the formation of this peculiar structural features is possible by selecting the basic structure forming phenomena well known in materials science and solid state physics (nucleation, crystal growth, grain growth) [50][51][52][53][54]. These phenomena are composed of elementary atomic processes, and can give account for the global effects of the atomic processes on the structure evolution.…”

Mechanisms of subgrain coarsening and its effect on the mechanical properties of carbon-supersaturated nanocrystalline hypereutectoid steel

“…In summary, the most likely mechanism for the depletion of Mn near the subgrain boundaries and the partitioning of Mn into cementite is suggested to proceed in terms of two processes: first, Mn atoms are captured at subgrain boundaries by boundary migration; second, the captured Mn atoms diffuse along the subgrain boundaries or triple junctions into cementite. A similar sweeping mechanism has been proposed by Uray and Menyhárd to explain the segregation of iron at grain boundaries and secondphase particles in tungsten [61]. However, their analysis was performed on the basis of an indirect measurement of electrical resistivity.…”

Growth of <i>a</i>-axis Textured Pulsed Laser Deposited VO<SUB>2</SUB> Nanostructures on Glass Substrate

“…The development of the structure in polycrystalline thin films is a very complex process and displays different features in different stages of film growth [15]. Considering the structure development of real polycrystalline thin films; the effects of the deposition parameters on the structure and the appearance of particular structural features, it can be concluded that a comprehensive description of the formation of these particular structural features is possible by following the basic structure-forming phenomena well known in materials science and solid-state physics (nucleation, crystal growth, grain growth) [13,14,15,30,31,32,33,34]. These processes are composed of elementary atomic processes, and can account for the global effects on the structure evolution [15].…”