Comprehensive effect of hydrostatic compressive stress in retained austenite on mechanical properties and hydrogen embrittlement of martensitic steels

Low alloy TRIP steel is expected to be applied to automobile bodies because of its high strength, high ductility, and excellent impact properties and press formability. It has been reported that the low alloy TRIP steel of hydrogen embrittlement resistance is improved by utilizing the hydrogen storage characteristics of highly stable retained austenite. Therefore, for the purpose of increasing the volume fraction of retained austenite, it was produced at various cooling rates below the martensite transformation start temperature. As a result, the volume fraction of retained austenite increased, and then the effect of hydrogen embrittlement decreased. The matrix phase and retained austenite is refined with decrees of the cooling rate. It is considered that the size and surface area of the retained austenite also affected the improvement of hydrogen embrittlement resistance.

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Effects of Alloying Elements Addition on Delayed Fracture Properties of Ultra High-Strength TRIP-Aided Martensitic Steels

Metals ◽

10.3390/met10010006 ◽

2019 ◽

Vol 10 (1) ◽

pp. 6 ◽

Cited By ~ 4

Author(s):

Tomohiko Hojo ◽

Junya Kobayashi ◽

Koh-ichi Sugimoto ◽

Akihiko Nagasaka ◽

Eiji Akiyama

Keyword(s):

Hydrogen Embrittlement ◽

Retained Austenite ◽

Hydrogen Diffusion ◽

High Strength ◽

Alloying Elements ◽

Bending Test ◽

Hydrogen Trapping ◽

Martensitic Steels ◽

Diffusible Hydrogen ◽

Martensite Matrix

To develop ultra high-strength cold stamping steels for automobile frame parts, the effects of alloying elements on hydrogen embrittlement properties of ultra high-strength low alloy transformation induced plasticity (TRIP)-aided steels with a martensite matrix (TM steels) were investigated using the four-point bending test and conventional strain rate tensile test (CSRT). Hydrogen embrittlement properties of the TM steels were improved by the alloying addition. Particularly, 1.0 mass% chromium added TM steel indicated excellent hydrogen embrittlement resistance. This effect was attributed to (1) the decrease in the diffusible hydrogen concentration at the uniform and fine prior austenite grain and packet, block, and lath boundaries; (2) the suppression of hydrogen trapping at martensite matrix/cementite interfaces owing to the suppression of precipitation of cementite at the coarse martensite lath matrix; and (3) the suppression of the hydrogen diffusion to the crack initiation sites owing to the high stability of retained austenite because of the existence of retained austenite in a large amount of the martensite–austenite constituent (M–A) phase in the TM steels containing 1.0 mass% chromium.

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Recent Progress of Low and Medium-Carbon Advanced Martensitic Steels

Metals ◽

10.3390/met11040652 ◽

2021 ◽

Vol 11 (4) ◽

pp. 652

Author(s):

Koh-ichi Sugimoto

Keyword(s):

Mechanical Properties ◽

Fatigue Strength ◽

Retained Austenite ◽

Case Hardening ◽

Martensitic Steels ◽

Delayed Fracture ◽

Medium Carbon ◽

Warm Working ◽

Hardening Process ◽

Vacuum Carburization

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm- working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, good cold-formability, superior toughness and fatigue strength, and delayed fracture strength due to a mixture of martensite and retained austenite, compared with the conventional martensitic steels. In addition, the hot- and warm-stamping and forging contribute to enhance the mechanical properties of the AMSs due to grain refining and the improvement of retained austenite characteristics. The case-hardening process (fine particle peening and vacuum carburization) is effective to further increase the fatigue strength.

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Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽

10.3390/ma14092323 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2323

Author(s):

Yubing Du ◽

Zhiqing Zhao ◽

Qiang Xiao ◽

Feiting Shi ◽

Jianming Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Size Effect ◽

Compressive Stress ◽

Failure Modes ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Aggregate Concrete ◽

Substitution Ratio ◽

The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

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The Effect of Different Annealing Strategies on the Microstructure Development and Mechanical Response of Austempered Steels

Metals ◽

10.3390/met11071041 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1041

Author(s):

Eliseo Hernandez-Duran ◽

Luca Corallo ◽

Tanya Ros-Yanez ◽

Felipe Castro-Cerda ◽

Roumen H. Petrov

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Mechanical Response ◽

Steel Grade ◽

The Other ◽

Microstructure Development ◽

Microstructural Refinement ◽

Heterogeneous Distribution ◽

Parent Austenite ◽

Conventional Annealing

This study focuses on the effect of non-conventional annealing strategies on the microstructure and related mechanical properties of austempered steels. Multistep thermo-cycling (TC) and ultrafast heating (UFH) annealing were carried out and compared with the outcome obtained from a conventionally annealed (CA) 0.3C-2Mn-1.5Si steel. After the annealing path, steel samples were fast cooled and isothermally treated at 400 °C employing the same parameters. It was found that TC and UFH strategies produce an equivalent level of microstructural refinement. Nevertheless, the obtained microstructure via TC has not led to an improvement in the mechanical properties in comparison with the CA steel. On the other hand, the steel grade produced via a combination of ultrafast heating annealing and austempering exhibits enhanced ductility without decreasing the strength level with respect to TC and CA, giving the best strength–ductility balance among the studied steels. The outstanding mechanical response exhibited by the UFH steel is related to the formation of heterogeneous distribution of ferrite, bainite and retained austenite in proportions 0.09–0.78–0.14. The microstructural formation after UFH is discussed in terms of chemical heterogeneities in the parent austenite.

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Effect of Hydrogen on Mechanical Properties of Pipeline API 5L X70 Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.146.213 ◽

2011 ◽

Vol 146 ◽

pp. 213-225 ◽

Cited By ~ 4

Author(s):

T. Bellahcene ◽

J. Capelle ◽

Méziane Aberkane ◽

Z. Azari

Keyword(s):

Mechanical Properties ◽

Hydrogen Embrittlement ◽

Hydrogen Absorption ◽

Fatigue Tests ◽

The Finite Element Method ◽

Effective Distance ◽

Bending Tests ◽

Fatigue Initiation ◽

Api 5L X70 Steel ◽

Special Soil

The aim of this work is to study the effects of hydrogen absorption on mechanical properties of pipe API 5L X70 steel. This study is conducted in special soil solution NS4 with pH 6.7 It show that the tensile properties like yield stress, ultimate strength and elongation at failure reduced under hydrogen embrittlement. Several fatigue tests (three (03) points bending tests) on roman tile specimens with notch are performed. Fatigue initiation is detected by acoustic emission. A comparison between specimens electrolytically charged with hydrogen and specimens without hydrogen absorption is made and it has been noted that fatigue initiation time is reduced when hydrogen embrittlement occurs. The field of elastoplastic stresses near the notch is computed by the finite-element method with the Abaqus software package. Effective distance and stress are calculated with the volumetric approach and the Notch intensity Factor of the roman tile specimen is determined for each loading value used in our tests.

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Effect of Si Content on Microstructure and Properties of 60Si2CrVA Spring Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.968.63 ◽

2014 ◽

Vol 968 ◽

pp. 63-66 ◽

Cited By ~ 1

Author(s):

Fei Zhao ◽

Zhan Ling Zhang ◽

Jun Shuai Li ◽

Cui Ye ◽

Ni Li

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Volume Fraction ◽

Testing Machine ◽

Spring Steel ◽

Impact Testing ◽

X Ray ◽

Comprehensive Properties ◽

Spring Steels ◽

Si Content

The microstructure and mechanical properties of the four spring steels with different Si content treated by Q-I-Q-T process were studied by metallographic microscope, MTS, impact testing machine and X-ray stress analyzer. The results show that the tensile strength and yield strength is first increased and then decreased with the increase of Si content, the volume fraction of retained austenite and elongation are fist decreased and then increased when the Si content is less than 2.1%, and the microstructure become finer and homogeneous. When Si content reaches 2.1%, the comprehensive properties of 60Si2CrVA spring steel is the best.

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Microstructure and Properties of a Non-Quenched Prehardened Steel at Different Cooling Rate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.1976 ◽

2012 ◽

Vol 524-527 ◽

pp. 1976-1979

Author(s):

Yi Luo ◽

Jin Ming Peng

Keyword(s):

Mechanical Properties ◽

Fine Structure ◽

Optical Microscopy ◽

Cooling Rate ◽

Retained Austenite ◽

Transformation Products ◽

Electronic Microscopy ◽

Transmission Electronic Microscopy ◽

Microstructure And Properties ◽

Cooling Conditions

Mechanical properties of non-quenched prehardened (NQP) steel air cooled and sand cooled after forged were tested and their microstructure was investigated by optical microscopy and transmission electronic microscopy(TEM). The results show that mechanical properties of the NQP steel are similar at both cooling conditions, and their microstructure is bainite, whose fine structure is main bainite ferrite laths, retained austenite films, retained austenite islands and their transformation products. Bainite ferrite laths of the NQP steel air cooled are narrower than that sand cooled, while more retained austenite islands exist in latter.

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Microstructure and Mechanical Properties of a Low-Carbon Steel Treated by One-Step Quenching and Partitioning Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1082.202 ◽

2014 ◽

Vol 1082 ◽

pp. 202-207 ◽

Cited By ~ 1

Author(s):

Shu Yan ◽

Xiang Hua Liu

Keyword(s):

Mechanical Properties ◽

Carbon Steel ◽

Microstructural Evolution ◽

Retained Austenite ◽

Uniform Elongation ◽

Low Carbon Steel ◽

Total Elongation ◽

Low Carbon ◽

Quenching And Partitioning ◽

Partitioning Time

A low carbon steel was treated by quenching and partitioning (Q&P) process, and a detailed characterization of the microstructural evolution and testing of mechanical properties were carried out. The resulted mechanical properties indicate that with the partitioning time increasing, the tensile strength decreases rapidly first and then remains stable, and the total elongation increases first then decreases. The investigated steel subjected to Q&P process exhibits excellent products of strength and elongation (17.8-20.6 GPa•%). The microstructural evolution of martensite matrix during the partitioning step was observed, and the morphology and content of retained austenite were characterized. The working hardening behavior of the samples was analyzed, and the retained austenite with higher carbon content contributes to the uniform elongation more effectively.

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Effects of Cryogenic Treatment on the Microstructure and Mechanical Properties of High-alloyed Tool Steels

HTM Journal of Heat Treatment and Materials ◽

10.1515/htm-2020-750505 ◽

2020 ◽

Vol 75 (5) ◽

pp. 73-93

Author(s):

Alwin Schulz ◽

Chengsong Cui ◽

Matthias Steinbacher ◽

Tuncer Ümit ◽

Martin Wunde ◽

...

Keyword(s):

Mechanical Properties ◽

Wear Resistance ◽

Retained Austenite ◽

Cryogenic Treatment ◽

Homogeneous Distribution ◽

Tool Steels ◽

Positive Effects ◽

Heat Treated ◽

Primary Carbides ◽

Complete Transformation

Abstract In this work, the influence of a cryogenic treatment on the microstructure, mechanical properties and wear resistance of the high-alloyed tool steels X38CrMoV5-3, X153CrMoV12 and ~X190CrVMo20-4 were investigated. Based on tempering curves of the steels, the heat treatment parameters were determined for the mechanical and wear specimens so that the conventionally heat-treated steels and the cryogenically treated steels featured similar hardness. The investigations showed that an almost complete transformation of retained austenite and a more homogeneous distribution of secondary carbides in the microstructure could be achieved by incorporating a cryogenic treatment. However, the cryogenic treatment does not show significantly positive effects on the investigated mechanical properties and wear resistance of the tool steels. The wear resistance of the samples was dominated by primary carbides. The cryogenic treatment would have a positive effect on large tool components with large wall thicknesses in terms of uniform and complete transformation of retained austenite throughout the entire components.

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