Tensile Behavior of Medium-Mn Steels that Exhibit Two-stage TRIP Behavior

Abstract

Medium manganese steels often demonstrate dynamic strain aging (serrated flow stress) and rapid work hardening. Tensile behavior of three medium manganese steels is studied in both the hot band condition and a cold worked and batch annealed condition. Starting microstructures were a combination of γ-austenite, e-martensite, a-martensite, and α-ferrite. Intrinsic stacking fault energies calculated at room temperature, varied between -2.1 and 0.7 mJ/m2. Tensile strengths ranged from 1310 MPa to 1404 MPa with total elongations of 24.8% to 34.1%. Interrupted tensile tests were performed and x-ray diffraction was used to characterize the strained microstructures. All three alloys showed evidence of two-stage TRIP where the starting microstructure TRIP'd in sequence of γ-→ϵ→α or ϵ→α One of the alloys was modified with 4.6 wt. pet. Cr and dynamic strain aging was observed in a fully austenitized and quenched condition, whereas the serrated flow was reduced as a result of M23(C,N)6 precipitation during batch annealing for 20 hours at 600°C. Two different mechanisms of dynamic strain aging were identified: one being dislocation pining and unpinning in ferrite related to nitrogen and the second related to Mn ordering in stacking faults associated with the close packed structures.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Dynamic strain aging; Intercritical annealing; Medium-Mn; Two-stage TRIP

International Standard Book Number (ISBN)

978-193511767-4

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Association for Iron and Steel Technology, All rights reserved.

Publication Date

01 Jan 2017

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