\"A regular solution model was developed to calculate the chemical driving force for α-martensite formation, ΔGλ→ αChem. A model for the strain energy, ΔGλ→αstr, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The MαS was determined at a temperature at which ΔGλ→αChem + ΔGλ→αstr = 0. In conjunction with a previously developed ε-martensite model, a means of predicting the volume fraction of λ-austenite was determined; and it was shown that for values of ΔMs < 0, defined as Msε - Msα produced the greatest amounts of retained γ-austenite in the as quenched microstructure. These models were tested, and confirmed, with a new alloy formulated to produce a steel with chromium replacing the traditional aluminum to obtain a ΔMs = -100 C° that exhibited the two-stage TRIP behavior. From this substitution the dynamic strain aging response could be mitigated through M₂₃(C,N)₆ precipitation trapping carbon and nitrogen. The work hardening behavior of these steels was found to be due to the Stage II (ε→α) martensitic reaction and not the dynamic strain aging of the steels. Eight medium-Mn steels were processed and it was found that when the intrinsic stacking fault energy was less than 10.5 mJ/m² the two-stage TRIP response was activated. Empirical relationships for the strength and ductility were determined for the two-stage TRIP steels. The developed models have been used to optimize alloy composition and a designed steel with composition Fe-13.8Mn-1.0Si-3.0Cr-0.15C-0.003N (wt. pct.) is recommended for future investigation\"--Abstract, page iv.
","abstract_html":"<p>"A regular solution model was developed to calculate the chemical driving force for α-martensite formation, ΔG<sup>λ→ α</sup><sub>Chem</sub>. A model for the strain energy, ΔG<sup>λ→α</sup><sub>str</sub>, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The M<sup>α</sup><sub>S</sub> was determined at a temperature at which ΔG<sup>λ→α</sup><sub>Chem</sub> + ΔG<sup>λ→α</sup><sub>str</sub> = 0. In conjunction with a previously developed ε-martensite model, a means of predicting the volume fraction of λ-austenite was determined; and it was shown that for values of ΔMs < 0, defined as Ms<sup>ε</sup> - Ms<sup>α</sup> produced the greatest amounts of retained γ-austenite in the as quenched microstructure. These models were tested, and confirmed, with a new alloy formulated to produce a steel with chromium replacing the traditional aluminum to obtain a ΔMs = -100 C° that exhibited the two-stage TRIP behavior. From this substitution the dynamic strain aging response could be mitigated through M₂₃(C,N)₆ precipitation trapping carbon and nitrogen. The work hardening behavior of these steels was found to be due to the Stage II (ε→α) martensitic reaction and not the dynamic strain aging of the steels. Eight medium-Mn steels were processed and it was found that when the intrinsic stacking fault energy was less than 10.5 mJ/m² the two-stage TRIP response was activated. Empirical relationships for the strength and ductility were determined for the two-stage TRIP steels. The developed models have been used to optimize alloy composition and a designed steel with composition Fe-13.8Mn-1.0Si-3.0Cr-0.15C-0.003N (wt. pct.) is recommended for future investigation"--Abstract, page iv.</p>","abstract_has_math":false,"creators":["Field, Daniel M."],"institution":"Missouri University of Science and Technology","degree_name":"Ph. D. in Metallurgical Engineering","degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T03:18:43Z","subjects":["EBSD","Martensite","Phase Transformation","TRIP Steels","Metallurgy"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/2672","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Field, Daniel M."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["Dissertation - Open Access"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. D. in Metallurgical Engineering"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Missouri University of Science and Technology"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["EBSD","Martensite","Phase Transformation","TRIP Steels","Metallurgy"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/2672"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"A regular solution model was developed to calculate the chemical driving force for α-martensite formation, ΔGλ→ αChem. A model for the strain energy, ΔGλ→αstr, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The MαS was determined at a temperature at which ΔGλ→αChem + ΔGλ→αstr = 0. In conjunction with a previously developed ε-martensite model, a means of predicting the volume fraction of λ-austenite was determined; and it was shown that for values of ΔMs < 0, defined as Msε - Msα produced the greatest amounts of retained γ-austenite in the as quenched microstructure. These models were tested, and confirmed, with a new alloy formulated to produce a steel with chromium replacing the traditional aluminum to obtain a ΔMs = -100 C° that exhibited the two-stage TRIP behavior. From this substitution the dynamic strain aging response could be mitigated through M₂₃(C,N)₆ precipitation trapping carbon and nitrogen. The work hardening behavior of these steels was found to be due to the Stage II (ε→α) martensitic reaction and not the dynamic strain aging of the steels. Eight medium-Mn steels were processed and it was found that when the intrinsic stacking fault energy was less than 10.5 mJ/m² the two-stage TRIP response was activated. Empirical relationships for the strength and ductility were determined for the two-stage TRIP steels. The developed models have been used to optimize alloy composition and a designed steel with composition Fe-13.8Mn-1.0Si-3.0Cr-0.15C-0.003N (wt. pct.) is recommended for future investigation\"--Abstract, page iv.
"]},{"key":"dc:title","label":"Title","values":["Chemistry, design, and processing of two-stage TRIP steel"]}]}],"canonical_facts":{"dc:creator":["Field, Daniel M."],"dc:description.abstract":["\"A regular solution model was developed to calculate the chemical driving force for α-martensite formation, ΔGλ→ αChem. A model for the strain energy, ΔGλ→αstr, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The MαS was determined at a temperature at which ΔGλ→αChem + ΔGλ→αstr = 0. In conjunction with a previously developed ε-martensite model, a means of predicting the volume fraction of λ-austenite was determined; and it was shown that for values of ΔMs < 0, defined as Msε - Msα produced the greatest amounts of retained γ-austenite in the as quenched microstructure. These models were tested, and confirmed, with a new alloy formulated to produce a steel with chromium replacing the traditional aluminum to obtain a ΔMs = -100 C° that exhibited the two-stage TRIP behavior. From this substitution the dynamic strain aging response could be mitigated through M₂₃(C,N)₆ precipitation trapping carbon and nitrogen. The work hardening behavior of these steels was found to be due to the Stage II (ε→α) martensitic reaction and not the dynamic strain aging of the steels. Eight medium-Mn steels were processed and it was found that when the intrinsic stacking fault energy was less than 10.5 mJ/m² the two-stage TRIP response was activated. Empirical relationships for the strength and ductility were determined for the two-stage TRIP steels. The developed models have been used to optimize alloy composition and a designed steel with composition Fe-13.8Mn-1.0Si-3.0Cr-0.15C-0.003N (wt. pct.) is recommended for future investigation\"--Abstract, page iv.
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/2672"],"dc:subject":["EBSD","Martensite","Phase Transformation","TRIP Steels","Metallurgy"],"dc:title":["Chemistry, design, and processing of two-stage TRIP steel"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Metallurgical Engineering"],"thesis:institution_name":["Missouri University of Science and Technology"]},"updated_at":"2026-07-24T03:18:43Z"}