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

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dc.contributor.advisorBall, Anthonyen_ZA
dc.contributor.authorSchaffer, G Ben_ZA
dc.date.accessioned2016-10-25T13:33:41Z
dc.date.available2016-10-25T13:33:41Z
dc.date.issued1983en_ZA
dc.descriptionBibliography: pages 79-86.en_ZA
dc.description.abstractThis 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.identifier.apacitationSchaffer, G. B. (1983). <i>A constitutional study of a dual phase steel containing 12% chromium</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Materials Engineering. Retrieved from http://hdl.handle.net/11427/22294en_ZA
dc.identifier.chicagocitationSchaffer, G B. <i>"A constitutional study of a dual phase steel containing 12% chromium."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Materials Engineering, 1983. http://hdl.handle.net/11427/22294en_ZA
dc.identifier.citationSchaffer, G. 1983. A constitutional study of a dual phase steel containing 12% chromium. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Schaffer, G B AB - 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. DA - 1983 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1983 T1 - A constitutional study of a dual phase steel containing 12% chromium TI - A constitutional study of a dual phase steel containing 12% chromium UR - http://hdl.handle.net/11427/22294 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22294
dc.identifier.vancouvercitationSchaffer GB. A constitutional study of a dual phase steel containing 12% chromium. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Materials Engineering, 1983 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22294en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentCentre for Materials Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMaterials Scienceen_ZA
dc.titleA constitutional study of a dual phase steel containing 12% chromiumen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc (Applied Science)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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