On the strain hardening of austempered spheroidal graphite cast iron: Dissertation

Jouko Vuorinen

Research output: ThesisDissertationMonograph

Abstract

The properties of austempered spheroidal graphite cast iron are surveyed.It has found many applications in engineering.The microstructure of its matrix consists essentially of metastable austenite and bainite, which in turn consists of ferrite laths and plates imbedded in the austenite.There is no cementite in the structure.Owing to the remarkable amount of the austenite in the structure the properties differ in many respects from the properties of ordinary spheroidal graphite cast irons and steels.Structural changes caused by deformation were studied by transmission electron microscopy.Ion bombardment technique was used'in preparing the thin foils for the TEM studies.The austenite amounts were measured by magnetic scales.The strain hardening mechanism due to monotonic compression at room temperature was studied in detail.Shear bands, identifed to be deformation twins in the austenite, are caused by plastic deformation.Intersections of twins are nucleation sites for #martensite.The structure of the strain-induced martensite is very fine, needle-like, due to the thinness of the twins.The increasing strain increases the number of the twin-twin intersections, and thus the number of martensite needles.The orientation relationship between the strain-induced martensite and parent austenite is the Kurdyumov-Sachs relationship.The strainhardening caused by cyclic loading due to rolling contact was studied also.It turned out to be caused essentially by high dislocation density.The strain-hardening characteristics were measured using plane strain compression and tensile tests.The characteristics were compared with those of austenitic steels referred to in the literature.The steels displayed higher strain-hardening exponents.Causes for the difference are proposed.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Helsinki University of Technology
Place of PublicationEspoo
Publisher
Print ISBNs951-38-1339-8
Publication statusPublished - 1981
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

strain hardening
austenite
casts
graphite
martensite
iron
steels
needles
intersections
cementite
bainite
transmission electron microscopy
compression tests
plane strain
tensile tests
plastic deformation
bombardment
ferrites
foils
nucleation

Cite this

Vuorinen, J. (1981). On the strain hardening of austempered spheroidal graphite cast iron: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Vuorinen, Jouko. / On the strain hardening of austempered spheroidal graphite cast iron : Dissertation. Espoo : VTT Technical Research Centre of Finland, 1981. 69 p.
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abstract = "The properties of austempered spheroidal graphite cast iron are surveyed.It has found many applications in engineering.The microstructure of its matrix consists essentially of metastable austenite and bainite, which in turn consists of ferrite laths and plates imbedded in the austenite.There is no cementite in the structure.Owing to the remarkable amount of the austenite in the structure the properties differ in many respects from the properties of ordinary spheroidal graphite cast irons and steels.Structural changes caused by deformation were studied by transmission electron microscopy.Ion bombardment technique was used'in preparing the thin foils for the TEM studies.The austenite amounts were measured by magnetic scales.The strain hardening mechanism due to monotonic compression at room temperature was studied in detail.Shear bands, identifed to be deformation twins in the austenite, are caused by plastic deformation.Intersections of twins are nucleation sites for #martensite.The structure of the strain-induced martensite is very fine, needle-like, due to the thinness of the twins.The increasing strain increases the number of the twin-twin intersections, and thus the number of martensite needles.The orientation relationship between the strain-induced martensite and parent austenite is the Kurdyumov-Sachs relationship.The strainhardening caused by cyclic loading due to rolling contact was studied also.It turned out to be caused essentially by high dislocation density.The strain-hardening characteristics were measured using plane strain compression and tensile tests.The characteristics were compared with those of austenitic steels referred to in the literature.The steels displayed higher strain-hardening exponents.Causes for the difference are proposed.",
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Vuorinen, J 1981, 'On the strain hardening of austempered spheroidal graphite cast iron: Dissertation', Doctor Degree, Helsinki University of Technology, Espoo.

On the strain hardening of austempered spheroidal graphite cast iron : Dissertation. / Vuorinen, Jouko.

Espoo : VTT Technical Research Centre of Finland, 1981. 69 p.

Research output: ThesisDissertationMonograph

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T1 - On the strain hardening of austempered spheroidal graphite cast iron

T2 - Dissertation

AU - Vuorinen, Jouko

PY - 1981

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N2 - The properties of austempered spheroidal graphite cast iron are surveyed.It has found many applications in engineering.The microstructure of its matrix consists essentially of metastable austenite and bainite, which in turn consists of ferrite laths and plates imbedded in the austenite.There is no cementite in the structure.Owing to the remarkable amount of the austenite in the structure the properties differ in many respects from the properties of ordinary spheroidal graphite cast irons and steels.Structural changes caused by deformation were studied by transmission electron microscopy.Ion bombardment technique was used'in preparing the thin foils for the TEM studies.The austenite amounts were measured by magnetic scales.The strain hardening mechanism due to monotonic compression at room temperature was studied in detail.Shear bands, identifed to be deformation twins in the austenite, are caused by plastic deformation.Intersections of twins are nucleation sites for #martensite.The structure of the strain-induced martensite is very fine, needle-like, due to the thinness of the twins.The increasing strain increases the number of the twin-twin intersections, and thus the number of martensite needles.The orientation relationship between the strain-induced martensite and parent austenite is the Kurdyumov-Sachs relationship.The strainhardening caused by cyclic loading due to rolling contact was studied also.It turned out to be caused essentially by high dislocation density.The strain-hardening characteristics were measured using plane strain compression and tensile tests.The characteristics were compared with those of austenitic steels referred to in the literature.The steels displayed higher strain-hardening exponents.Causes for the difference are proposed.

AB - The properties of austempered spheroidal graphite cast iron are surveyed.It has found many applications in engineering.The microstructure of its matrix consists essentially of metastable austenite and bainite, which in turn consists of ferrite laths and plates imbedded in the austenite.There is no cementite in the structure.Owing to the remarkable amount of the austenite in the structure the properties differ in many respects from the properties of ordinary spheroidal graphite cast irons and steels.Structural changes caused by deformation were studied by transmission electron microscopy.Ion bombardment technique was used'in preparing the thin foils for the TEM studies.The austenite amounts were measured by magnetic scales.The strain hardening mechanism due to monotonic compression at room temperature was studied in detail.Shear bands, identifed to be deformation twins in the austenite, are caused by plastic deformation.Intersections of twins are nucleation sites for #martensite.The structure of the strain-induced martensite is very fine, needle-like, due to the thinness of the twins.The increasing strain increases the number of the twin-twin intersections, and thus the number of martensite needles.The orientation relationship between the strain-induced martensite and parent austenite is the Kurdyumov-Sachs relationship.The strainhardening caused by cyclic loading due to rolling contact was studied also.It turned out to be caused essentially by high dislocation density.The strain-hardening characteristics were measured using plane strain compression and tensile tests.The characteristics were compared with those of austenitic steels referred to in the literature.The steels displayed higher strain-hardening exponents.Causes for the difference are proposed.

M3 - Dissertation

SN - 951-38-1339-8

T3 - Technical Research Centre of Finland. Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

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Vuorinen J. On the strain hardening of austempered spheroidal graphite cast iron: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1981. 69 p.