Three-dimensional observations of morphology of low-angle boundaries in ultra-low carbon lath martensite

2017 ◽  
Vol 66 (6) ◽  
pp. 380-387 ◽  
Author(s):  
Shigekazu Morito ◽  
Anh Hoang Pham ◽  
Takuya Ohba ◽  
Taisuke Hayashi ◽  
Tadashi Furuhara ◽  
...  
Keyword(s):  
Lath Martensite ◽  
Three Dimensional ◽  
Low Carbon

Investigation of Three-Dimensional Geometry of Butterfly Martensite and Analysis of Relationship between Hardness of Lath/Butterfly Two-Phase Martensite and its Grain Thickness in Medium-Carbon Steel

2021 ◽  
Vol 1016 ◽  
pp. 1039-1044
Author(s):  
Takayoshi Niho ◽  
Keisuke Nagato ◽  
Masayuki Nakao
Keyword(s):  
Carbon Steel ◽  
Ion Beam ◽  
Lath Martensite ◽  
High Carbon Steel ◽  
Three Dimensional ◽  
Medium Carbon Steel ◽  
Thin Plates ◽  
Low Carbon ◽  
Two Phase ◽  
Medium Carbon

Medium-carbon steel with approximately 0.6 wt% carbon is widely used for mechanical applications, because the martensite contained in it is harder than that of low-carbon and high-carbon steel. The microstructure of steel martensite varies depending on the carbon content, and the microstructure of medium-carbon steel martensite are a mixture of lath martensite (LM) and butterfly martensite (BM). The geometry of LM grains are thin plates having thicknesses of 0.2–0.5 μm. As for BM, some researches demonstrated that the region of martensite spreads in the depth direction of the observation surface. However, the three-dimensional geometry of BM grains remains unclear. Through cross-sectional observation using focused ion beam (FIB), the present study demonstrates that one BM grain is formed via collision of two plates. Previous research shows that the hardness of LM is inversely correlated with the thickness of the grains. The FIB observation result indicates that geometry of LM and BM grains are both plate-like. In the present study, whether the same relationship is valid for the mixture of LM and BM grains is investigated. The results show that the hardness of medium-carbon steel martensite increases according to the decrease in thickness of constituent grains of the two-phase structure of LM and BM.

scholarly journals Three Dimensional Analyses of Low Angle Boundaries in Ultra-low Carbon Lath Martensite

Materia Japan ◽  
2016 ◽  
Vol 55 (12) ◽  
pp. 594-594
Author(s):  
Shigekazu Morito ◽  
Anh Hoang Pham ◽  
Takuya Ohba ◽  
Taisuke Hayashi ◽  
Tadashi Furuhara ◽  
...  
Keyword(s):  
Lath Martensite ◽  
Three Dimensional ◽  
Low Carbon

scholarly journals Lath Martensite Microstructure Modeling: A High-Resolution Crystal Plasticity Simulation Study

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 691
Author(s):  
Francisco-José Gallardo-Basile ◽  
Yannick Naunheim ◽  
Franz Roters ◽  
Martin Diehl
Keyword(s):  
High Resolution ◽  
Mechanical Behavior ◽  
Crystal Plasticity ◽  
Lath Martensite ◽  
Three Dimensional ◽  
Building Blocks ◽  
Quantitative Agreement ◽  
Carbon Steels ◽  
Plastic Behavior ◽  
Austenitic Phase

Lath martensite is a complex hierarchical compound structure that forms during rapid cooling of carbon steels from the austenitic phase. At the smallest, i.e., ‘single crystal’ scale, individual, elongated domains, form the elemental microstructural building blocks: the name-giving laths. Several laths of nearly identical crystallographic orientation are grouped together to blocks, in which–depending on the exact material characteristics–clearly distinguishable subblocks might be observed. Several blocks with the same habit plane together form a packet of which typically three to four together finally make up the former parent austenitic grain. Here, a fully parametrized approach is presented which converts an austenitic polycrystal representation into martensitic microstructures incorporating all these details. Two-dimensional (2D) and three-dimensional (3D) Representative Volume Elements (RVEs) are generated based on prior austenite microstructure reconstructed from a 2D experimental martensitic microstructure. The RVEs are used for high-resolution crystal plasticity simulations with a fast spectral method-based solver and a phenomenological constitutive description. The comparison of the results obtained from the 2D experimental microstructure and the 2D RVEs reveals a high quantitative agreement. The stress and strain distributions and their characteristics change significantly if 3D microstructures are used. Further simulations are conducted to systematically investigate the influence of microstructural parameters, such as lath aspect ratio, lath volume, subblock thickness, orientation scatter, and prior austenitic grain shape on the global and local mechanical behavior. These microstructural features happen to change the local mechanical behavior, whereas the average stress–strain response is not significantly altered. Correlations between the microstructure and the plastic behavior are established.

Laser Forming for Flexible Fabrication

2000 ◽  
Vol 16 (02) ◽  
pp. 97-109
Author(s):  
Koichi Masubuchi ◽  
Jerry E. Jones
Keyword(s):  
Three Dimensional ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
Cost Benefit ◽  
Network Models ◽  
High Strength ◽  
Laser Forming ◽  
Low Carbon ◽  
Flat Plates ◽  
Neural Network Models

A 36-month program supported by the Defense Advanced Research Projects Agency (DARPA) was conducted to demonstrate the feasibility to predictably laser form a variety of ferrous and non-ferrous metals of different thickness. Laser forming provides a method of producing complex shapes in sheet, plate, and tubing without the use of tooling, molds, or dies. By heating a localized area with a laser beam, it is possible to create stress states that result in predictable deformation. This research program has developed, refined and demonstrated constitutive and empirical, and neural network models to predict deformation as a function of critical parametric variables and established an understanding of the effect of laser forming on some metallurgical properties of materials. The program was organized into two, time-phased tasks. The first task involved forming flat plates to one-dimensional (I -D) shapes, such as, hinge bends in various materials including low-carbon steel, high-strength steels, nickel-based super alloys, and aluminum alloys. The second task expanded the work conducted in the first task to investigate three-dimensional (3-D) configurations. The models were updated, 3-D specimens fabricated and evaluated, and cost benefit analyses were performed.

The Effect of Severe Plastic Deformation on the Brittle-Ductile Transition in Low Carbon Steel

2009 ◽  
Vol 633-634 ◽  
pp. 471-480
Author(s):  
Masaki Tanaka ◽  
Kenji Higashida ◽  
Tomotsugu Shimokawa
Keyword(s):  
Fracture Toughness ◽  
Carbon Steel ◽  
Grain Boundaries ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Dislocation Dynamics ◽  
Strain Rates ◽  
Low Carbon ◽  
Dislocation Source ◽  
Brittle Ductile Transition

Brittle-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various temperatures and strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the controlling process of the BDT was not changed by the deformation with the ARB process. It was deduced that the decrease in the BDT temperature by grain refining was not due to the increase in the dislocation mobility controlled by short-range barriers. Quasi-three-dimensional simulations of dislocation dynamics, taking into account of crack tip shielding due to dislocations, were performed to investigate the effect of a dislocation source spacing along a crack front on the BDT. The simulation indicated that the BDT temperature is decreased with decreasing in the dislocation source spacing. Molecular dynamics simulations revealed that moving dislocations were impinged against grain boundaries and were reemitted from there with increasing strain. It indicates that grain boundaries can be new sources in ultra-fine grained materials, which increases toughness at low temperatures.

scholarly journals Morphological and Crystallographic Characteristics of α Structure in a Low-Carbon Iron–Nickel Alloy

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 468 ◽  
Author(s):  
Gaojun Mao ◽  
Cyril Cayron ◽  
Xiuli Mao ◽  
Rui Cao ◽  
Roland Logé ◽  
...  
Keyword(s):  
Lath Martensite ◽  
Granular Bainite ◽  
Body Centered Cubic ◽  
Low Carbon ◽  
Electron Backscattered Diffraction ◽  
Dislocation Densities ◽  
Lath Bainite ◽  
Crystallographic Characteristics ◽  
Iron Nickel ◽  
Relationship Of

The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, it is of interest to explore possible discrepancies between lath martensite and lath bainite from a crystallographic perspective. These microstructures were obtained by various cooling rates (i.e., water quenching, 5 °C/s, and 0.05 °C/s) and then were characterized by a combination of scanning electron microscopy and electron backscattered diffraction techniques. It is shown that: (1) Lath martensite (LM) formed in the samples that were water-quenched, and a mixture of LM and lath bainite (LB) and granular bainite (GB) formed in the samples cooled at rates of 5 °C/s and 0.05 °C/s, respectively; (2) A Kurdjumov-Sachs relationship was mostly found in as-quenched martensite, while a Greninger-Troiano relationship represented the orientation relationship of LB and GB; (3) As the cooling rate decreased, the dislocation densities in corresponding microstructures were reduced, while the tendency of variant grouping was enhanced.

scholarly journals Evaluation Model and Strategy for Selecting Carbon Reduction Technology for Campus Buildings in Primary and Middle Schools in the Yangtze River Delta Region, China

2020 ◽  
Vol 12 (2) ◽  
pp. 534
Author(s):  
Xiaoyu Luo ◽  
Cong Ma ◽  
Jian Ge
Keyword(s):  
Middle Schools ◽  
Water Conservation ◽  
Energy Use ◽  
Evaluation Model ◽  
Three Dimensional ◽  
Yangtze River Delta ◽  
Technology Selection ◽  
Low Carbon ◽  
Carbon Reduction ◽  
Yangtze River Delta Region

Cutting down global warming and reducing greenhouse gas emissions such as carbon dioxide are important global targets. Accounting for a third of global energy consumption, the building construction industry is an important target for carbon reduction. Campus buildings, of which there are a large number in China, differ from other building types, as they have noteworthy energy-use characteristics and technology selection requirements. This study identifies the carbon reduction technologies in Chinese primary and middle schools commonly used for energy and water conservation, and then evaluates their performance according to degrees of carbon reduction, maturity and economic suitability. Based on these three indicators, the study creates a three-dimensional evaluation model for the different technologies examined in order to obtain a selection ranking. The study offers guidance for project practice in the construction of primary and middle schools and helps to promote the development of the low-carbon campus.

scholarly journals Characterization of Microstructure in High-Hardness Surface Layer of Low-Carbon Steel

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 995
Author(s):  
Haitao Xiao ◽  
Shaobo Zheng ◽  
Yan Xin ◽  
Jiali Xu ◽  
Ke Han ◽  
...  
Keyword(s):  
Surface Layer ◽  
Carbon Steel ◽  
Yield Strength ◽  
Carbon Content ◽  
Acicular Ferrite ◽  
Lath Martensite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Upper Bainite ◽  
Mixed Microstructure

Surface hardening improves the strength of low-carbon steel without interfering with the toughness of its core. In this study, we focused on the microstructure in the surface layer (0–200 μm) of our low-carbon steel, where we discovered an unexpectedly high level of hardness. We confirmed the presence of not only upper bainite and acicular ferrite but also lath martensite in the hard surface layer. In area of 0–50 μm, a mixed microstructure of lath martensite and B1 upper bainite was formed as a result of high cooling rate (about 50–100 K/s). In area of 50–200 μm, a mixed microstructure of acicular ferrite and B2 upper bainite was formed. The average nanohardness of the martensite was as high as 9.87 ± 0.51 GPa, which was equivalent to the level reported for steel with twenty times the carbon content. The ultrafine laths with an average width of 128 nm was considered to be a key cause of high nanohardness. The average nanohardness of the ferrites was much lower than for martensite: 4.18 ± 0.39 GPa for upper bainite and 2.93 ± 0.30 GPa for acicular ferrite. Yield strength, likewise, was much higher for martensite (2378 ± 123 MPa) than for upper bainite (1007 ± 94 MPa) or acicular ferrite (706 ± 72 MPa). The high yield strength value of martensite gave the surface layer an exceptional resistance to abrasion to a degree that would be unachievable without additional heat treatment in other steels with similar carbon content.

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