Search

A three-dimensional magnetohydrodynamic model of an inductively coupled plasma depositor has been developed and applied to describe the process of outside vapor deposition during manufacturing of preforms for optical fibers. The steady state continuity, momentum, enthalpy and diffusion equations are solved consistently with the energy coupling accomplished through the electromagnetic field of an induction coil and the radiation losses from the plasma. Local thermodynamic equilibrium, steady and laminar flow, and optically thin plasma are assumed. A chemical surface reaction serving as a boundary condition for species mass fractions in the fluid is set to describe the deposition process. The model supplies information about the flow and temperature distribution of the fluid, the electromagnetic field, and the deposition rate on the target surfaces for complex real geometries.

Nitrified carbonless Fe-Ni-Cr stainless steels possess high tensile strengths and ductility, corrosion resistance and stability, hence they represent an attractive material for practical application. The nitrogen improves the mechanical parameters of austenitic steels but the problem of their corrosion resistance, hardening and thermal stability is connected with the composition as well as with the formation of martensite under external stress and plastic deformation. The authors reached the conclusion that the formation of martensite in some nitrified austenite-ferrite stainless steels leads to effective strengthening and conservation of high ductility. However for machine elements which operate at low and high temperature the appearance of deformation martensite decreases the alloy stability. The study of cyclic deformation of an Fe-18Cr-6.5Ni-0.19C alloy demonstrates the existence of a critical value of the strain amplitude necessary to provoke the formation of martensitic phase. The height of this energy barrier for {gamma}-{alpha} transition at fixed temperature is strongly dependent on the characteristics of substitutional and interstitial atoms. When this barrier is overcome, if the free energy values satisfy the relation F{sup {alpha}} < F{sup {gamma}}, the transition is realized at high velocity. This work is a continuation of the earlier study of nitrified alloys, and its aim ismore » to correlate the composition of austenitic Fe-Cr-Ni-N alloys with the formation of {alpha}-phase in the process of plastic deformation using X-ray and neutron diffraction methods.« less

The martensitic transformation of austenitic stainless steels can be induced by thermal treatment or by plastic deformation. The aim of present study is to determine the quantity and type of the phases formed after ultimate shearing strain at room temperature of austenitic Fe-Cr-Mn-N alloy as a function of nitrogen content. X-ray and neutron diffraction methods have been used in order to identify the new phases arising and their amount. These techniques are based on different scattering mechanism and the data obtained permit them to establish more precisely the correlation between the nitrogen content and structural transformation of the initial austenitic phase.