A constitutional study of a dual phase steel containing 12% chromium

 

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dc.contributor.advisor Ball, Anthony en_ZA
dc.contributor.author Schaffer, G B en_ZA
dc.date.accessioned 2016-10-25T13:33:41Z
dc.date.available 2016-10-25T13:33:41Z
dc.date.issued 1983 en_ZA
dc.identifier.citation Schaffer, G. 1983. A constitutional study of a dual phase steel containing 12% chromium. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/22294
dc.description Bibliography: pages 79-86. en_ZA
dc.description.abstract This thesis involved a study of the phase transfonnations in a chromium containing corrosion resistant dual phase steel, designated 3CR12. The objectives included the detennination of time-temperature-transformation (TTT) diagrams for the transformations between austenite and ferrite and an investigation into the factors controlling these reactions. The austenite decomposition reaction for a high nickel alloy, 3CR12Ni, and the effect of varying titanium concentrations on the equilibrium phases present in 3CR12, were also examined. Dilatometry was used to determine the transformation temperatures between austenite and ferrite and the Ms temperatures for the alloys investigated. The kinetics of the reactions were investigated by optical microscopy using two different etching techniques while the volume fractions of the various constituents were determined by a point counting method. Transmission electron microscopy was used to study the carbide morphologies and the nucleation and growth modes of the phases during the transformations. The distribution of the alloy elements were determined by microhardness measurements, an electronprobe microanalysis and a Kevex spectrometer attached to a scanning electron microscope. The 3CR12 alloy used in this study did not become fully austenitic above the Ae₃; it lies in the nose of the gamma loop of the Fe-Cr phase diagram. Two temperature regimes were identified on the decomposition of austenite. At 750°c the existing ferrite grains grew into the austenite matrix, while at 650° C and 700°C new ferrite was sympathetically nucleated i.e. it was heterogeneously nucleated on existing ferrite/austenite grain boundaries. Two types of carbide morphologies were formed. These were random precipitation within the ferrite grains and interphase precipitation. The TTI diagram showed conventional "C" curve kinetics. The austenitisation reaction occurred by a para-equilibrium mechanism. The rate controlling process was the structural change from ferrite to austenite; the reaction was not long range diffusion controlled. The speed of the reaction increased continuously with increasjng transformation temperature. No growth of ferrite occurred on isothermal transformation of 3CR12Ni at temperatures below the Ae₁. Increasing the bulk titanium content increased the Ms, Ae₁ and Ae₃ temperatures of 3CR12 due to the removal of carbon from, and the addition of titanium to, solution. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Materials Science en_ZA
dc.title A constitutional study of a dual phase steel containing 12% chromium en_ZA
dc.type Thesis / Dissertation en_ZA
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Engineering & the Built Environment en_ZA
dc.publisher.department Centre for Materials Engineering en_ZA
dc.type.qualificationlevel Masters en_ZA
dc.type.qualificationname MSc (Applied Science) en_ZA
uct.type.filetype Text
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