Precipitation In Stainless Steel Research Articles

Influence of Solid-Liquid Composite Casting on Interface and Microstructure of High Chromium Cast Iron

High chromium cast iron and stainless steel bimetal were fabricated by liquid-solid composite casting .The interface diffusion behavior and microstructure evolution of high chromium cast iron were studied. The results indicated that interface element diffusion behavior between stainless steel and high chromium cast iron was obviously existed. Under experimental conditions, there were many refined grainy-shaped carbides precipitation in stainless steel near interface, located at austenite grain boundary and intragranular austenite. As for high chromium cast iron, the morphology of the carbides varied from the interface to the specimen edge. The rod shaped carbides approached to composite interface were finer and become coarser rod-like or blade-like with increased distance from the composite interface. The reasons for elements diffusion and microstructure change were associated with alloys contents and temperature field.

Overview of Intermetallic Sigma () Phase Precipitation in Stainless Steels

The phase which exists in various series of stainless steels is a significant subject in steels science and engineering. The precipitation of the phase is also a widely discussed aspect of the science and technology of stainless steels. The microstructural variation, precipitation mechanism, prediction method, and effects of properties of phase are also of importance in academic discussions. In the first section, a brief introduction to the development and the precipitation characteristics (including morphologies and precipitation sites) of phase in stainless steels is presented. In the second section, the properties effect, prediction method, processing effect, elemental addition, retardation method and Thermo-Calc simulation of the phase in stainless steels are highlighted.

Analysis of heat-affected zone formation for laser cutting of stainless steel

A numerical study has been performed for the development of the heat-affected zone during the laser cutting of 304 stainless steel. This numerical study uses an analytical solution of the energy balance at the cutting front surface to determine the steady-state kerf shape. For a constant workpiece velocity, a transient numerical model can be made up for a two-dimensional plane normal to the workpiece velocity. From the time-temperature response of the workpiece material in this plane, the extent of the heat-affected zone (HAZ) can be determined. The results obtained through laser cutting experiments show good agreement with numerical estimates of the HAZ extent, as defined by grain refinement, impurities and possible carbide precipitation in stainless steel 304. This method also provide a computationally-efficient method compared with three-dimensional finite-element analysis.

Deformation Effects on Intragranular Carbide Precipitation and Transgranular Chromium Depletion in Type 316 Stainless Steels

Abstract Grain matrix or transgranular (TG) chromium depletion in type 316 stainless steels (SS) has been observed to be strain and heat treatment dependent, yielding C-curve behavior on a time-temperature-strain-TG corrosion map. The strain effect dominates above 16 to 20 percent showing increased TG corrosion and decreased time to develop TG depletion with increasing strain level. Higher temperatures also reduce the time to develop grain matrix attack, while isothermal holding for longer times produces higher amounts of TG corrosion in SS. Transgranular depletion is caused by precipitation of carbides within grain-matrix regions. Specifically, defect sites created during straining are favored locations for intragranular precipitation in SS. Regions of high dislocation density, deformation twin-stacking fault planes and twin-fault intersections were identified to be preferred sites for grain matrix precipitation during transmission electron microscopy (TEM) of 16 to 35 percent deformed SS.

Application of convergent beam electron microscopy in materials science

IntroductionWe have used a Philips EM400 electron microscope with a STEM pole- piece to carry out convergent beam electron microscopy on a wide variety of materials, including precipitates in stainless steels, metal/semiconductor contacts, metal oxide catalysts, environmental fibres, metastable phases in evaporated films, and transition metal chalcogenide layer compounds. Two features of this microscope make it particularly suitable for convergent beam work. These are its low hydrocarbon partial pressure which greatly reduces the carbon contamination of the specimen when working with a small probe (̴ 300 Ådiameter) and the very wide angular field of view in the diffraction plane (̴ 16°).Two-dimensional diffraction may be used to yield information about the projected crystal potential. In certain cases a simple relationship has been established between the form of zone axis patterns and the nature of the projected potential, Oneway of using this information is by making measurements of zone axis critical voltages and we have recently extended our measurements to a number of zone axis patterns with 6 mm symmetry having different sorts of projected potential.

Irradiation enhanced precipitation in stainless steel

Abstract Experimental findings of an irradiation enhancement of precipitation in stainless steel under observation in the High Voltage Electron Microscope (HVEM) are presented. The results for the case of electron irradiation are compared with previous studies of precipitation under neutron irradiation in thermal and fast reactor conditions. Under low neutron fluxes precipitation is influenced by the production of vacancy clusters which act as nuclei. However, growth of these nuclei is limited unless the temperature is sufficiently high for thermal diffusion to be significant. Under fast reactor conditions the high neutron fluxes permit growth to continue at irradiation temperatures ≳450°c, under the irradiation enhanced diffusion. The observations made in the HVEM show that the production of vacancy clusters is not necessary for precipitation to occur under irradiation. Growth takes place rapidly under the defect supersaturations provided by the electron beam. Extension of the theory of irradiation enhan...