The solidification sequence in an 18-8 stainless steel, investigated by directional solidification
01 Nov 1972-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science (Springer New York)-Vol. 3, Iss: 11, pp 2989-2997
TL;DR: In this paper, the authors applied the directional solidification technique to investigate the complicated solidification sequence in a commercial austenitic stainless steel which was known to yield a primary precipitation of § ferrite when cast into a 5 tons ingot.
Abstract: The directional solidification technique was applied in order to investigate the complicated solidification sequence in a commercial austenitic stainless steel which was known to yield a primary precipitation of § ferrite when cast into a 5 tons ingot. Three stages of solidification were found. The first precipitation of § ferrite was interrupted by precipitation of austenite and at the end of the solidification there was a transition back to precipitation of § ferrite. The competition between the first two stages is affected by the cooling rate and the nitrogen content. The precipitation of austenite from the melt results in the usual coring whereas o ferrite forms with a very homogeneous composition, presumably due to rapid diffusion in this phase. On cooling austenite forms from the § ferrite and this reaction also results in coring, presumably due to rapid diffusion in § ferrite.
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TL;DR: The solidification of peritectic alloys, including both nucleation and growth, is reviewed in this paper, where the authors define various compositions associated with binary per-itectic systems, their equilibrium solidification, multicomponent per-architectic system, and metastable phases.
Abstract: The solidification of peritectic alloys is reviewed, including both nucleation and growth. The introduction defines various compositions associated with binary peritectic alloys, their ‘equilibrium’ solidification, multicomponent peritectic systems, and metastable phases in peritectic systems. Nucleation studies are reviewed according to the rate of cooling and the type of specimen. Some comparisons are made with observations in eutectic alloys. At fast cooling rates metastable events can occur, as reviewed for alloys based on the Al-Ti and other systems. Growth studies in peritectic alloys have identified three stages: the ‘reaction’ (three phases in contact); the ‘transformation’ (the peritectic phase thickens by solid state diffusion); and ‘direct solidification’ of the peritectic phase. Models of the stages are outlined and compared with experiment for various binary alloys, followed by a summary of observations of peritectic solidification in multicomponent Fe-Cr-Ni and Fe-C-X alloys. Recent ...
297 citations
TL;DR: The microstructures of austenitic stainless steel welds typically contain a variety of complex austenite-ferrite structures and this behavior is related to solidification cracking susceptibility as discussed by the authors.
Abstract: The microstructures of austenitic stainless steel welds typically contain a variety of complex austenite-ferrite structures. These structures are a result of both the solidification behaviour and subsequent solid state transformations which are controlled by both composition and weld cooling rates. The solidification cracking susceptibility is directly related, in a complex fashion, to the solidifying weld structure. The solidification and solid state transformations which occur during welding are reviewed in detail and this behaviour is related to solidification cracking susceptibility. Improved understanding of these phenomena offers an opportunity to improve commercial applications of austenitic stainless steels.
275 citations
01 Dec 1986-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the authors analyzed the diffusion and redistribution of solutes in dendrites during the solidification of carbon steel, and found that the diffusion in the phase δ-phase and the redistribution during δ/γ transformation played an important role in the variation of the interdendritic concentrations of the solutes with lower carbon concentration.
Abstract: Solute distribution in dendrites during solidification of carbon steel was analyzed by unidirectional solidification experiments and mathematical analysis. The characteristic of the mathematical analysis is that diffusion of solutes in solid and redistribution of solutes at solid/liquid andδ/γ interfaces are taken into consideration. Based on the observed and calculated results, it was found that phosphorus was redistributed fromγ-phase toδ-phase, and that manganese was slightly redistributed fromδ-phase toγ-phase. Therefore the concentrated region of phosphorus can be separated from that of manganese duringδ/γ transformation in the case of slow cooling. Moreover, it was concluded that rapid diffusion inδ-phase and the redistribution duringδ/γ transformation played an important role in the variation of the interdendritic concentrations of solutes with lower carbon concentration.
205 citations
TL;DR: In this article, the columnar to equiaxed transition (CET) in solidified alloys is considered and a review of the current level of understanding of the CET and current modelling capabilities are summarised and assessed.
Abstract: The generally reported observations pertinent to any proposed interpretation of the columnar to equiaxed transition (CET) in as solidified alloys are initially considered. The review then proceeds to consider the proposed mechanisms of equiaxed grain formation, the influence of alloy and processing conditions on the CET, criteria for the termination of columnar growth and, finally, deterministic/stochastic models for predicting the CET. In conclusion, the present level of understanding of the CET and current modelling capabilities are summarised and assessed.
204 citations
TL;DR: In this article, the macro-and microstructures of about fifty different stainless welds of the AISI/ AWS 300 series are analyzed under conditions corresponding to a typical shielded metal arc (SMA) welding the welds with a ratio in the range 1.48 and 1.95, respectively.
Abstract: The macro-and microstructures of about fifty different stainless welds of the AISI/ AWS 300 series are analyzed. The results indicate that under conditions corresponding to a typical shielded metal arc (SMA) welding the welds with a ratio in the range 1.48≾Cr
eq
/Ni
eq
≾1.95, where Ni
eq
and Cr
eq
are the nickel and chromium equivalents on the Schaeffler diagram, solidify in accordance with a duplex mode with the delta ferrite as the primary (leading) phase. The austenite forms between ferrite dendrites through a three-phase reaction between liquid, ferrite and austenite, and subsequently grows into the ferrite by either an equiaxial or an acicular mechanism, resulting in a drastic decrease in the volume fraction of the delta ferrite. The micro-structure at room temperature is characterized by a general irregularity and the varied morphology of the ferrite. The compositional differences observed at room temperature are a consequence both of the solidification and the solid state transformation.
194 citations