Title: Temperature-dependent micromechanical behavior of medium-Mn transformation-induced-plasticity steel studied by in situ synchrotron X-ray diffraction

Abstract

The temperature-dependent micromechanical behavior of medium-Mn transformation-induced-plasticity (TRIP) steel with a nominal chemical composition of Fe-0.1C-10Mn-2Al (mass%) fabricated by intercritical annealing 650 ºC for 1 h after cold-rolling, was investigated using in situ high-energy X-ray diffraction (HE-XRD) with uniaxial tensile tests at temperatures of 100, 25 and -50 ºC. We find that as the deformation temperature decreases, the Luders strain decreases and more austenite transforms to martensite during Luders band propagation. The Luders bands are associated with sudden changes of lattice strain in austenite. At 100 ºC, austenite is too stable to transform to martensite, resulting in limited work-hardening capability and a relatively low strain to failure. At 25 ºC, the austenite is found to transform in bursts during applied loading. These transformations correlate with stepwise peak broadening in the austenite phase and are attributed to Portevin-Le Chatelier (PLC) band propagation. At -50 ºC, we then observe a more intense TRIP effect which suppresses PLC band formation and leads to a high ultimate tensile strength. In addition to the TRIP effect, we find that work hardening in the deformation-induced martensite phase plays an important role in the plastic stability at low temperature, by accommodating stress compatibility between grains and phases.more » Our studies provide the first direct experimental evidence for the existence of large stress concentrations in the austenite phase near the Luders band propagation front. These observations help to deepen understanding of the complex temperature-dependent micromechanical behaviors of advanced medium-Mn TRIP steels.« less

Authors:

Zhang, Minghe ^[1]; Li, Longfei ^[2]; Ding, Jie ^[2]; Wu, Qingbao ^[2]; Wang, Yan-Dong ^[2]; Almer, Jonathan ^[3]; Guo, Fangmin ^[3]; Ren, Yang ^[3]

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+ Show Author Affiliations

1. Univ. of Science and Technology Beijing (China). State Key Lab. for Advanced Metals and Materials and Collaborative Innovation Center of Steel Technology; Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS) and X-ray Science Division
2. Univ. of Science and Technology Beijing (China). State Key Lab. for Advanced Metals and Materials
3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS) and X-ray Science Division

Publication Date:

Thu Sep 14 00:00:00 EDT 2017

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Natural Science Foundation of China (NSFC); Ministry of Education (MOE) (China)

OSTI Identifier:

1461272

Alternate Identifier(s):

OSTI ID: 1549950

Grant/Contract Number:  

AC02-06CH11357; 51471032; 51231002; 51527801; 06111020; 06111040; 2016Z-01; 2016Z-12; 2016Z-19

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 141; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Austenite stability; High-energy X-ray diffraction; Load partitioning; Medium-Mn TRIP steel