Ultrahigh tensile strength over 1200 MPa has not been reported for low-density delta-transformation-induced-plasticity (δ-TRIP) steels. In addition, the trade-off between strength and ductility is still inevitable for those steels. This study fills the gap by controlling morphology and volume fraction of δ-ferrite. A micro-alloyed low-density δ-TRIP steel with a chemical composition of Fe–3Al-0.84Cr-0.94Mn-0.31Mo-1.18Ni-0.31Si-0.25V-0.3C (weight percentage, wt.%) was prepared, and the high Al addition resulted in the reduced density of ∼5% with 7.49 g cm−3 in density. By applying varying heat treatment parameters, three steels with different microstructures, i.e. steels A, B and C were prepared. Microstructural morphologies of the three steels are significantly different. Steel A has a medium volume fraction of 56% for dendritic δ-ferrite with moderate average thickness of 3 μm while steel B contains the highest volume fraction of dendritic δ-ferrite (61%) with the smallest thickness of 1 μm. In contrast, steel C has the lowest volume fraction of dendritic δ-ferrite (32%) with the largest thickness of 4 μm. In addition, the volume fractions of lamellar RA are 14%, 8% and 19% for steels A, B and C, respectively. Steel A has an ultrahigh tensile strength of 1270 MPa, while a good ductility of 17% is retained. However, steel B shows the lower ductility of 14% in spite of the higher tensile strength of 1220 MPa. The thickness and volume fraction of δ-ferrite band influence not only the TRIP effect but also the initiation and propagation of cracks. The main reason for steel B with the lower ductility is associated with its smallest thickness and the highest volume fraction of δ-ferrite among the three steels. In contrast, the utmost strength-ductility product of steel C is attributed to its moderate thickness and the lowest volume fraction of δ-ferrite bands, which can alleviate the local stress concentration at the ferrite/martensite boundaries and leads to the improvement of ductility. 

Microstructural evolution and mechanical properties of a micro-alloyed low-density δ-TRIP steel

The impact of microstructure evolution on the mechanical properties of a typical 500 MPa-grade weathering steel produced by an identical thermo-mechanical control process and different tempering treatments at 450–650 °C were thoroughly investigated mainly using scanning electron microscopy (SEM) equip with an electron backscatter diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM), and X-ray diffractometer (XRD). Results indicated that the as-rolled steel consists of granular bainitic ferrite (GBF) and a considerable amount of martensite/austenite (M/A) constituents, exhibiting unsatisfied mechanical properties. As the tempering temperature increased from 450 to 550 and 650 °C, the massive twin-type M/A constituents decomposed preferentially into carbides following the sequence of Fe3C→(Cr, Mn, Fe)3C→(Cr, Mn, Fe)3C + (Cr, Mn)23C6, with a small amount of fine lath-type M/A constituents remained. The matrix recovered with the bainitic ferrite laths merged, the dislocation density decreased and the proportion of high-angle grain boundary (HAGB) increased. Nanoscale (Ti, Nb)C and ε-Cu particles also precipitated simultaneously, leading to an increase of yield strength. The strain hardening capacity and hence the tensile strength reduced resulting from the decomposition of M/A constituents. Moreover, the impact toughness was first enhanced by tempering at 450–600 °C with the decreasing twin-type M/A constituents content and increasing HAGBs proportion, and then deteriorated by tempering at 650 °C due to the precipitation of necklace-like M23C6 carbides at the grain boundaries. An optimum mechanical property combination was achieved via tempering at 550–600 °C. 

The impacts of M/A constituents decomposition and complex precipitation on mechanical properties of high-strength weathering steel subjected to tempering treatment

In the current work, the relationship between the microstructural evolution and strengthening mechanisms in a vanadium micro-alloyed high strength low alloy (HSLA) martensitic steel has been systematically investigated by multi-scale characterizations and modeling. Two heat treatment routes, i.e., solution quenching plus tempering (SQT) and solution quenching plus isothermal annealing (QIA) are applied to produce a martensitic matrix combined with considerable nano-scale MC-type carbides (M = V, Mo, Cr) in the experimental steels. Theoretic calculations of the strengthening contributions are conducted based on quantitative characterizations of microstructural parameters, the overall modeling results agree quite well with the experimental results for estimating yield strength of the specimens. Precipitation and dislocation strengthening are found to be the main factors causing strength evolution with different isothermal holding time (IHT) at 600 °C. In both SQT and QIA specimens, the prolonged IHT contributes to an increased particle size and volume fraction of MC precipitates but a decreased dislocation density, and the most excellent mechanical properties are achieved with IHT of 2 h. The precipitation strengthening of SQT specimens is higher than that of QIA specimens because of its finer particle size and higher volume fraction of the MC precipitates, resulting in the higher yield strength of the SQT specimens than that of the QIA specimens. This can be explained by the hierarchy lath martensite that is highly dislocated with numerous interfaces, providing considerable nucleation points and high-speed atomic diffusion paths for precipitation, leading to the significantly refined MC particle size in the SQT specimens. Moreover, the MC precipitates exhibit no significantly coarsening during isothermal holding at 600 °C, which is a result of the presence of Mo/Cr atoms in MC precipitates that yields precipitate size stabilization due to its higher chemical potentials than that of V, thus maintaining a stable precipitation strengthening after IHT exceeding 2 h. 

Effect of precipitation on the mechanical behavior of vanadium micro-alloyed HSLA steel investigated by microstructural evolution and strength modeling

This study explores the influence of build orientation on the microstructural and mechanical properties of Wire Arc Additive Manufactured (WAAM) Grade 91 Steel and Monel 400 bimetallic components, which are used in combined thermal and corrosion resistance applications. Microstructural analysis was conducted using techniques such as Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FE-SEM), and Transmission Electron Microscopy (TEM). The research specifically examines how different orientations (0˚, 45˚, and 90˚) affect the as-built properties of these bimetallic components. Mechanical properties were evaluated through tensile testing, revealing significant variations: Grade 91 steel displayed a tensile strength of 1235.2 ± 12 MPa at a 0˚ orientation and 1314.7 ± 5 MPa at 90˚, indicating anisotropic characteristics. Similarly, Monel 400 exhibited an increase in tensile strength from 491.5 ± 12 MPa at 0˚ to 517.7 ± 14 MPa at 45˚. Fractographic analysis indicates a predominantly ductile fracture mechanism. The results of the study are important for using WAAM to create bimetallic components for environments that combine strength, thermal resistance, and resistance to corrosion. 

Effect of Build Orientation on the Microstructure and Mechanical Properties of Wire Arc Additive Manufactured Grade 91 Steel/Monel 400 Bimetallic components

A new generation of multi-functional construction structural steel with high yield strength of ∼545 MPa, excellent toughness of ∼170 J/cm 2 at −20 °C, lower yield ratio smaller than 0.83, good fire resistance, and good corrosion resistance was successfully developed by thermo-mechanical controlled processing plus tempering. The effects of tempering on the microstructure and mechanical properties were investigated. The results show that although the bainite lath slightly coarsens and the dislocation density slightly decreases as the tempering temperature increases, the yield strength of the steel increases mainly due to the precipitation strengthening. The samples tempered at 300 °C show the best combination of strength, toughness, and yield ratio. In addition, the high-temperature strength of the newly developed Q460 steel is obviously higher than the conventional one, which is mainly attributed to the bainitic strengthening and precipitation strengthening. Moreover, a denser rust layer forms on the surface of new Q460 steel during corrosion because of the addition of Cr and Cu, which increases the corrosion resistance of the steel. 

Effect of Tempering on the Microstructure and Properties of a New Multi-Functional 460 MPa Grade Construction Structural Steel

The mechanical properties and precipitation behavior of hot-rolled microalloyed steels with varied Nb and V additions were investigated. The steels had a predominantly ferritic microstructure with a very good combination of strength ( σ U T S  = 800–1000 MPa), ductility (total elongation = 16–19%) and hole expansion ratio (32–34%). The strength increased with increasing Nb and V content. The stretch-flangeability of the steels did not deteriorate with increasing strength. The favorable hole expansion behavior of the steels is attributed to the fine ferrite grain size (1.6–1.8 μm) and uniformity of the microstructure, as well as the fine precipitates of Nb and V carbonitrides in the matrix. Nb carbonitrides formed during hot rolling and contributed to the grain refinement through their interaction with recrystallization. The co-precipitation of Nb and V carbonitrides during coiling was confirmed and characterized by 3D atom probe tomography. The formation of these fine precipitates contributed to further increase in the strength of the V-containing steel allowing the steel to achieve strength >1000 MPa.

Mechanical properties and precipitation behavior of high strength hot-rolled ferritic steel containing Nb and V

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Yaping Lu

Author Tools

Chat about Author

Papers

Mechanical properties and precipitation behavior of high strength hot-rolled ferritic steel containing Nb and V