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Title: Microstructure evolution in TRIP-aided seamless steel tube during T-shape hydroforming process

Transformation-induced plasticity aided seamless steel tube comprising of ferrite, bainite, and metastable austenite was processed through forging, piercing, cold-drawing, and two-stage heat treatment. T-shape hydroforming is a classic forming method for experimental research and practical production. The current work studied austenite-to-martensite transformation and microcrack initiation and propagation of the tube during T-shape hydroforming using electron backscattering diffraction, scanning electron microscopy, and transmission electron microscopy. The strain distribution in the bcc-phase and fcc-phase was studied by evaluating changes in the average local misorientation. Compared to the compressive stress, metastable austenite with similar strain surrounding or inside the grains transformed easier under tensile loading conditions. The inclusions were responsible for microcrack initiation. The propagation of the cracks is hindered by martensite/austenite constituent due to transformation induced plasticity effect. The volume fraction of untransformed retained austenite decreased with increase in strain implying transformation-induced plasticity effect. - Highlights: • Hydroformed tubes processed via TRIP concept • EBSD provided estimate of micro local strain. • Retained austenite hinders propagation of microcracks.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4]
  1. State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, Liaoning Provence (China)
  2. School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110004, Liaoning Provence (China)
  3. Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397 (Japan)
  4. Center for Structural and Functional Materials, University of Louisiana at Lafayette, 44130 Lafayette, LA 70504-4130 (United States)
Publication Date:
OSTI Identifier:
22403527
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 94; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AUSTENITE; BACKSCATTERING; BAINITE; BCC LATTICES; COMPARATIVE EVALUATIONS; CRACKS; DRAWING; ELECTRON DIFFRACTION; FCC LATTICES; FERRITE; FORGING; HEAT TREATMENTS; LOADING; MARTENSITE; MICROSTRUCTURE; PLASTICITY; SCANNING ELECTRON MICROSCOPY; STEELS; STRAINS; TRANSMISSION ELECTRON MICROSCOPY