Show simple item record

dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorAnsell, George S.
dc.contributorDoremus, R. H.
dc.contributorGisser, David G.
dc.contributorJudd, Gary
dc.contributorStoloff, N. S.
dc.contributor.authorStrife, James R.
dc.date.accessioned2021-11-03T08:51:16Z
dc.date.available2021-11-03T08:51:16Z
dc.date.created2017-07-27T09:53:07Z
dc.date.issued1976-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2009
dc.descriptionMay 1976
dc.descriptionSchool of Engineering
dc.description.abstractThe effect of austenite prestrain above the M(sub d) temperature on the structure and transformation kinetics of the subsequent martensitic transformation observed on cooling was determined for a series of Fe-Ni-Cr-C alloys. The alloys were designed to exhibit a shift in martensite morphology in the non-deformed state from twinned plate to lath while maintaining constant Mₛ temperature, carbon content, and austenite grain size. This was accomplished by varying the relative amounts of nickel and chromium. The transformation behavior was observed over the temperature range O°Cto -196°c as a function of tensile prestrains performed above the Md temperature. A range of prestrains from 5% o 45% was investigated. The pertinent observations were as follows.
dc.description.abstractThe results for these four alloys are discussed by considering the various parameters which may affect the transformation. These include the chemical free energy change as a function of temperature, the defect structure and overall strain hardening of the austenite, and finally, the morphology of the transformation product. It is concluded that the response of a given alloy to austenite prestrain above the M(sub d) temperature can be correlated with the morphology of the martensite observed in the non-deformed, as-quenched state. For the range of prestrains investigated, the transformation of austenite to lath martensite is much more susceptible to stabilization by austenite prestrain above the M(sub d) temperature than is the transformation of austenite to plate martensite.
dc.description.abstractThe effect of prestrain above the M(sub d) on the transformation in a stainless steel of a l6Cr-12Ni composition was also investigated. This alloy showed a lath morphology in the non-deformed state. Increasing level of prestrain above the M(sub d) was associated with a decrease in percent martensite transformed at -l96°c such that stabilization of the transformation was observed at 20% prestrain. There was no effect on the morphology of the transformation product but rather the growth of lath bands was inhibited.
dc.description.abstractNon-deformed specimens of a l6Cr-5Ni-O.3C alloy exhibited a lath morphology. Although the Mₛ decreased with increasing prestrain, the percent martensite transformed at -196°c increased, with respect to non-deformed samples for prestrains above the M(sub d) of less than 20%. A maximumin the stimulation effect was observed near 8% prestrain. This stimulation was associated with the nucleation of twinned plate martensite. The relative amount of lath martensite decreased with increasing prestrain above the M(sub d) so that a sample prestrained 20% showed predominantly plate martensite. A prestrain of 40% completely stabilized the transformation.
dc.description.abstractA twinned plate morphology was also observed for non-deformed specimens of a 9Cr-llNi-O.3C alloy. The habit plane was again {259] but no autocatalytic effect was observed. The Mₛ was continually decreased by increasing prestrain above the M(sub d). The rate of transformation to martensite was initially stabilized by prestrain but recovered entirely after 50°C undercooling below the Mₛ. The percent transformed at -196°c increased slightly in prestrained samples with respect to non-deformed samples again saturating at approximately 95%. Prestrain had no effect on the structure of the transformation product.
dc.description.abstractA 25Ni-O.3C alloy exhibited 'a burst transformation at the Mₛ in the non-deformed state consisting of {225}y chevron shaped plates and {259}y midribbed plates. The midribbed plates were autocatalytiy cally related while the chevrons were not. The presence of the chevrons was associated with a small burst size. An austenite prestrain above the M(sub d) temperature of l0% stabilized the formation of the chevrons and resulted in a large burst of midribbed plates. As the level of prestrain above the M(sub d) increased, the burst temperature increased but the amount of transformation accompanying the burst decreased. This was related to a refinement in martensite plate size and a restriction on the number of operating variants of the habit plane. Prestrain had no effect on the sUbstructure of the large plates. These were internally twinned on {112}ₘ The percent transformed saturated at 95% on progressive undercooling below the Mₛ temperature for all levels of prestrain.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectPhysical metallurgy
dc.titleThe influence of austenite prestrain above the M(sub d) temperature on the martensitic tranformation in Fe-Ni-Cr-C alloys
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid178436
dc.digitool.pid178437
dc.digitool.pid178438
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Materials Engineering


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record