Effect of cathodic hydrogen-charging current density on mechanical properties of prestrained high strength steels

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

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The Study of Microstructure and Mechanical Properties of Two High Strength Steels

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/730/1/012026 ◽

2020 ◽

Vol 730 ◽

pp. 012026

Author(s):

Shihan Li ◽

Xiaolin Wang ◽

Wei Zhao ◽

Zunzhao Li

Keyword(s):

Mechanical Properties ◽

High Strength Steels ◽

High Strength ◽

Microstructure And Mechanical Properties

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Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.344.143 ◽

2007 ◽

Vol 344 ◽

pp. 143-150 ◽

Cited By ~ 6

Author(s):

Gianluca Buffa ◽

Livan Fratini ◽

Marion Merklein ◽

Detlev Staud

Keyword(s):

Mechanical Properties ◽

Stress Condition ◽

Research Effort ◽

High Strength Steels ◽

High Strength ◽

Tensile Tests ◽

Friction Stir ◽

Tailored Blanks ◽

Sheet Stamping ◽

Wide Range

Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide range of the thickness ratios has been considered. The formability of the obtained blanks has been characterized through tensile tests and cup deep drawing tests, in order to show the formability in dependency of the stress condition; what is more mechanical and metallurgical investigations have been made on the welded joints.

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Application of Quenching-Partitioning-Tempering Process in Hot Rolled Plate Fabrication

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.82 ◽

2010 ◽

Vol 654-656 ◽

pp. 82-85 ◽

Cited By ~ 3

Author(s):

Shu Zhou ◽

Ying Wang ◽

Nai Lu Chen ◽

Yong Hua Rong ◽

Jian Feng Gu

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

High Strength Steels ◽

High Strength ◽

Significant Fraction ◽

Rolled Plate ◽

Quenching And Partitioning ◽

Good Ductility ◽

Hot Rolled ◽

Rolled Plates

The quenching-partitioning-tempering (Q-P-T) process, based on the quenching and partitioning (Q&P) treatment, has been proposed for producing high strength steels containing significant fraction of film-like retained austenite and controlled amount of fine martensite laths. In this study, a set of Q-P-T processes for C-Mn-Si-Ni-Nb hot rolled plates are designed and realized. The steels with Q-P-T processes present a combination of high strength and relatively good ductility. The origin of such mechanical properties is revealed by microstructure characterization.

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The Role of Inclusions on Mechanical Properties in High Strength Steels

Journal of Vacuum Science and Technology ◽

10.1116/1.1317034 ◽

1972 ◽

Vol 9 (6) ◽

pp. 1339-1339 ◽

Cited By ~ 2

Author(s):

J. J. Hauser ◽

M. G. H. Wells ◽

I. Perlmutter

Keyword(s):

Mechanical Properties ◽

High Strength Steels ◽

High Strength

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Relationship between Microstructure and Mechanical Properties in Q&P-Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.1933 ◽

2016 ◽

Vol 879 ◽

pp. 1933-1938 ◽

Cited By ~ 1

Author(s):

Richard G. Thiessen ◽

Georg Paul ◽

Roland Sebald

Keyword(s):

Mechanical Properties ◽

Dual Phase Steel ◽

High Strength Steels ◽

High Strength ◽

The Body ◽

Advanced High Strength Steels ◽

Passenger Safety ◽

Back Scattering ◽

Body In White ◽

Expected Increase

Third-Generation advanced high strength steels are being developed with the goal of reducing the body-in-white weight while simultaneously increasing passenger safety. This requires not only the expected increase in strength and elongation, but also improved local formability. Optimizing elongation and formability were often contradictory goals in dual-phase steel developments. Recent results have shown that so-called "quench and partitioning" (Q&P) concepts can satisfy both requirements [1]. Many Q&P-concepts have been studied at thyssenkrupp Steel Europe. Thorough investigation of the microstructure has revealed relationships between features such as the amount, morphology and chemical stability of the retained austenite and the obtained mechanical properties. An evaluation of the lattice strain by means of electron-back-scattering-diffraction has also yielded a correlation to the obtained formability. The aim of this work is to present the interconnection between these microstructural features and propose hypotheses for the explanation of how these features influence the macroscopically observed properties.

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