Microstructure Characterization of Advanced High-Strength Automotive Steels

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 6438

Special Issue Editors


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Guest Editor
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Interests: alloys; rolling; mechanical properties; microstructure

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Guest Editor
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, China
Interests: steel; superalloy; phase transformations; microstructure; mechanical properties

E-Mail Website
Guest Editor
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Interests: alloys; textures; phase transformations; retained austenite

Special Issue Information

Dear Colleagues,

Current automotive designs utilize sheet steels and emphasize the optimization of both vehicle weight and performance. Advanced High-Strength Steels (AHSS) offer an opportunity for the development of cost-effective and light-weight parts with improved safety and optimized environmental performance for automotive applications. This Special Issue is devoted to the most recent advancements in advanced high-strength steel. The mechanical properties of AHSS steels are controlled by many factors, including phase composition and distribution in the overall microstructure, volume fraction, and the morphology of phase constituents, as well as the stability of metastable constituents. This research subject also serves as a forum for researchers to interact with one another. We welcome authors to submit original research articles as well as review articles for consideration in this Special Issue. This Special Issue focuses on novel developments in steel design and on new insights regarding processing–microstructure–property relationships in AHSS. Topics that might be considered include, but are not limited to, the following:

  1. Material design;
  2. Phase transformation;
  3. Microstructure characterization;
  4. Mechanical properties;
  5. Computations and simulations.

Prof. Dr. Zhengzhi Zhao
Prof. Dr. Jun Hu
Dr. Pengfei Gao
Guest Editors

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Keywords

  • TRIP
  • TRIP-aided bainitic ferrite (TBF) steel
  • TRIP-aided annealed martensite (TAM) steel
  • quenching and partitioning (QP) steel
  • dual phase steels with improved formability (DH)
  • complex phase steels with improved formability (CH)
  • TWIP
  • deformation
  • phase transformation
  • hydrogen embrittlement

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Published Papers (3 papers)

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Research

13 pages, 3188 KiB  
Article
Experimental and Modeling Study of Phase-Specific Flow Stress Distribution in Intercritically Annealed Quenching and Partitioning Steels
by Pengfei Gao, Feng Li, Ke An and Zhengzhi Zhao
Crystals 2022, 12(10), 1412; https://doi.org/10.3390/cryst12101412 - 6 Oct 2022
Cited by 2 | Viewed by 1633
Abstract
To meet the increasing demand and stringent requirements of automotive structural steels, intercritically annealed quenching and partitioning (QP) steels are attracting significant attention owing to their excellent strength–plasticity balance. However, to date, limited reports have focused on the correlation between the microstructure and [...] Read more.
To meet the increasing demand and stringent requirements of automotive structural steels, intercritically annealed quenching and partitioning (QP) steels are attracting significant attention owing to their excellent strength–plasticity balance. However, to date, limited reports have focused on the correlation between the microstructure and strength of intercritically annealed QP. In this study, the mechanical behaviors of QP steels with different Si contents were investigated by developing a physical-based mechanical model based on microstructural characterizations. In situ neutron diffraction was used to analyze the evolution of the phase constitution. Si content influenced the phase transformation behavior of the test steel. In the early stages of deformation, Si-strengthened steel exhibited lower retained austenite (RA) stability and faster transformation kinetics. The variation in the RA volume fraction with the deformation was fitted using a segmented exponential function. Based on the microstructure and strengthening mechanisms, a mechanical model considering grain refinement during phase transformation was proposed. The model was validated using intercritically annealed QP steels with different Si contents. The transformation-induced plasticity effect, that is, the contribution of RA to the strength, was discussed from two perspectives. Deformation-induced martensite (DIM) exhibited a significant work-hardening rate owing to the high solid solution strengthening by carbon and the high dislocation density. The residual RA after the DIM transformation exhibited a non-negligible stress distribution. Particularly, the grain boundary density and dislocations increased with strain, strengthening the remaining RA. Full article
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11 pages, 2980 KiB  
Article
Computational Simulation by Phase Field: Martensite Transformation Kinetics and Variant Selection under External Fields
by Chenchong Wang, Jiahua Yuan and Minghao Huang
Crystals 2022, 12(6), 829; https://doi.org/10.3390/cryst12060829 - 11 Jun 2022
Cited by 3 | Viewed by 2456
Abstract
Tailoring martensite transformation is critical for improving the mechanical properties of advanced steels. To provide preliminary guidance for the control of martensite transformation behaviour using external fields by computational simulation method, the phase-field method was used to calculate the morphology evolution, kinetics, and [...] Read more.
Tailoring martensite transformation is critical for improving the mechanical properties of advanced steels. To provide preliminary guidance for the control of martensite transformation behaviour using external fields by computational simulation method, the phase-field method was used to calculate the morphology evolution, kinetics, and variant selection of the martensite transformation under different loading modes and magnetic field intensities. The incubation, transformation, and stable stages of the three variants based on the Bain strain group were investigated using different kinetic curves. These results clearly indicate that both uniaxial tension and compression can greatly promote the formation of martensite during the transformation stage and cause an obvious preferred variant selection. In contrast, the different variants have relatively balanced forms under shearing conditions. In addition, the magnetic field is a gentler way to form a state with balanced variants than other techniques such as shearing. Additionally, all these simulation results are consistent with classical martensitic transformation theory and thermodynamic mechanism, which proves the rationality of this research. The aim of the present study was to provide qualitative guidance for the selection of external fields for microstructural improvement in advanced steels. Full article
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14 pages, 6818 KiB  
Article
Effect of B Addition on Microstructure and Mechanical Properties of High-Strength 13Mn TRIP Steel with Different Annealing Temperatures
by Feng Li, Pengfei Gao, Jie Liu, Yan Zhao, Tao Kang and Zhengzhi Zhao
Crystals 2022, 12(6), 776; https://doi.org/10.3390/cryst12060776 - 27 May 2022
Cited by 1 | Viewed by 1842
Abstract
The development of advanced high-strength steel has become the research focus of steel in order to meet low emission requirements. Different annealing temperatures from 600 °C to 900 °C were applied to 1200 MPa Grade 13Mn TRIP steels with (30B steel) or without [...] Read more.
The development of advanced high-strength steel has become the research focus of steel in order to meet low emission requirements. Different annealing temperatures from 600 °C to 900 °C were applied to 1200 MPa Grade 13Mn TRIP steels with (30B steel) or without B (0B steel). The effects of B addition on microstructure and mechanical properties with different annealing temperatures were investigated. Except for M2B in 30B steel, both steels annealed at 600 °C or 700 °C contained only austenite. When annealed at 800 °C or 900 °C, ε-martensite and α′-martensite were observed whereas 30B steel had less of them. 30B steel had higher yield strength (YS) and tensile strength (TS) regardless of the annealing temperature. Total elongation (TE) of 30B steel was smaller when annealed at 600 °C or 700 °C but larger at 800 °C or 900 °C. B addition refined austenite grains, and therefore depressed phase transformation to ε-martensite and α′-martensite during annealing. B addition enhanced YS and TS by refining grains, hindering dislocation movement and promoting phase transformation, but changed the fracture mechanism. The best TS × TE (53.62 GPa%) for 30B steel was reached when annealed at 800 °C. The more sufficiently triggered TRIP effect in high-temperature-annealed 30B steel accounts for its scarcely decreased TS and high TE. Full article
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