scholarly journals Quantification of the Dislocation Density, Size, and Volume Fraction of Precipitates in Deep Cryogenically Treated Martensitic Steels

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1561
Author(s):  
Ajesh Antony ◽  
Natalya M. Schmerl ◽  
Anna Sokolova ◽  
Reza Mahjoub ◽  
Daniel Fabijanic ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Size Distribution ◽  
Volume Fraction ◽  
Cryogenic Treatment ◽  
Atom Probe ◽  
Magnetic Scattering ◽  
Martensitic Steels ◽  
Deep Cryogenic Treatment ◽  
Nucleation Sites ◽  
Aisi D2

Two groups of martensitic alloys were examined for changes induced by deep cryogenic treatment (DCT). The first group was a range of binary and ternary compositions with 0.6 wt % carbon, and the second group was a commercial AISI D2 tool steel. X-ray diffraction showed that DCT made two changes to the microstructure: retained austenite was transformed to martensite, and the dislocation density of the martensite was increased. This increase in dislocation density was consistent for all alloys, including those that did not undergo phase transformation during DCT. It is suggested that the increase in dislocation density may be caused by local differences in thermal expansion within the heterogeneous martensitic structure. Then, samples were tempered, and the cementite size distribution was examined using small angle neutron scattering (SANS) and atom probe tomography. First principles calculations confirmed that all magnetic scattering originated in cementite and not carbon clusters. Quantitative SANS analysis showed a measurable change in cementite size distribution for all alloys as a result of prior DCT. It is proposed that the increase in dislocation density that results from DCT modifies the cementite precipitation through enhanced diffusion rates and increased cementite nucleation sites.

Evaluation of Deep Criogenic Treatment at Microabrasive Wear of Aisi D2 Steel

2015 ◽  
Vol 1120-1121 ◽  
pp. 1257-1263
Author(s):  
Cosme Roberto Moreira Silva ◽  
Tiago F.O. Melo ◽  
José A. Araújo ◽  
J.L.A. Ferreira ◽  
S.J. Gobbi
Keyword(s):  
Wear Resistance ◽  
Treatment Cycle ◽  
Cryogenic Treatment ◽  
Deep Cryogenic Treatment ◽  
Abrasive Resistance ◽  
Austenitization Temperature ◽  
Aisi D2 Steel ◽  
X Ray ◽  
Aisi D2 ◽  
D2 Steel

Wear resistance of tool steels can be increased with deep cryogenic treatment (DCT) application. Mechanisms related to DCT are still not completely understood. Microabrasive wear resistance of cryogenically treated samples of AISI D2 steel was evaluated in terms of austenitization temperature at heat treatment cycle and quenching steps related to DCT. X-ray difractometry, scanning and optical microscopy and quantitative evaluation of carbides with image analysis were carried out aiming material characterization. For samples subjected to higher austenitization temperatures, the DCT treatment does not increase abrasive wear resistance. For samples treated at lower austenitization temperature, the DCT treatment results on 44% increase at abrasive resistance. This effect is correlated to the increase of the amount of fine carbides distributed at samples matrices cryogenically treated.

Structure-Property Correlation of Cryotreated AISI D2 Steel

2010 ◽  
Vol 117 ◽  
pp. 49-54 ◽  
Author(s):  
Debdulal Das ◽  
Apurba Kishore Dutta ◽  
Kalyan Kumar Ray
Keyword(s):  
Wear Resistance ◽  
Cryogenic Treatment ◽  
Structure Property ◽  
Tool Steels ◽  
Deep Cryogenic Treatment ◽  
Aisi D2 Steel ◽  
Secondary Carbides ◽  
Varied Degree ◽  
Aisi D2 ◽  
D2 Steel

This study aims to reveal the underlying mechanism associated with the enhancement of wear resistance of tool steels by deep cryogenic treatment and to resolve the issue of reported varied degree of improvement in wear resistance through structure-property correlation of cryotreated vis-à-vis conventionally treated AISI D2 steel. Microstructures of heat treated specimens have been characterized employing various techniques with specific emphasis on quantitative estimation of the characteristics of secondary carbides. Evaluations of properties include measurements of bulk hardness, apparent strength of the matrix, fracture toughness and dry sliding wear resistance under wide rage of normal loads supplemented by in-depth characterizations of worn surfaces, wear debris and subsurfaces of worn specimens in order to identify the operative mode and mechanism of wear. It has been demonstrated that the favorable modifications of the precipitation behavior of secondary carbides in addition to removal of retained austenite are the governing mechanisms for the enhancement of wear resistance of tool steels by deep cryogenic treatment. The cause of the reported varied degree of improvement in wear resistance by deep cryogenic treatment has been explained by disparity of the operative modes and mechanisms of wear.

Microstructure of In Situ Particles/7055Al Matrix Composites with Deep Cryogenic Treatment

2012 ◽  
Vol 217-219 ◽  
pp. 114-118 ◽  
Author(s):  
Xun Yin Zhang ◽  
Gui Rong Li ◽  
Ting Wang Zhang ◽  
Lei Cao ◽  
Hong Ming Wang ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Cryogenic Treatment ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Deep Cryogenic Treatment ◽  
X Ray ◽  
Diffraction Peaks

Al2O3，Al3Ti and Al3Zr particles reinforced 7055 aluminium matrix composites were fabricated via melt reaction method. The volume fraction is controlled at about 4-5%. After extrusion and solution-aging heat treatment the sample was prepared for deep cryogenic treatment, The microstructure and evolution of mechanical properties of (Al3Ti+Al3Zr)p/7055 composites were analyzed using optical microscopy(OM),scanning electronic microscopy(SEM) and X-ray diffraction(XRD). Some θ(Al2Cu) phases with nanometer size precipitate in the inner grain. As some grains preferred orient the intensity of some main diffraction peaks increase. Compared with those of as-cast and squeezed states the micro hardness has increased by 16.8% and 10.0% separately.

Effect of Cryogenic Treatment on the Microstructure Modification of SKH51 Steel

2021 ◽  
Author(s):  
Kaweewat Worasaen ◽  
Piyada Suwanpinij ◽  
Karuna Tuchinda
Keyword(s):  
Wear Resistance ◽  
Volume Fraction ◽  
Cryogenic Treatment ◽  
Constant Load ◽  
Holding Time ◽  
Primary Carbide ◽  
Deep Cryogenic Treatment ◽  
Microstructure Modification ◽  
Conventional Heat Treatment ◽  
The Matrix

This research aimed to investigate the microstructure modification mechanism used to improve the hardness and wear resistance of SKH51 steel. The cryogenic treatment (CT), including both shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT), was used to modify the microstructure of SKH51 steel in this research. The effect of short and long holding time (12 and 36 h) in CT was studied. The microstructures were evaluated by using a light optical microscopy (LOM) and a scanning electron microscopy (SEM). The phase identifications of the matrix, carbides, and a-parameter of the matrix were analyzed by using X-ray diffraction (XRD). The M6C and MC carbides size, aspect ratio, and distribution were analyzed using digimizer image analysis software on the SEM micrographs. Micro-Vickers were employed to evaluate the hardness of the targeted samples. Wear tests were performed by using a 6 mm diameter WC ball as the indenter and 5-N-constant load with a ball-on-disk wear tester. The results suggested that the increase of the secondary carbide was caused by the contraction and expansion phenomena of the matrix’s lattice, forcing the carbon atom out and acting as the carbide nucleation. The influence of holding time in the SCT and DCT regions was different. For the SCT, increasing the holding time increased the volume’s fraction of MC carbide. Conversely, the M6C carbide size grew with increasing holding time in the DCT region, while no significant increase in the number of MC carbide was observed. The cryogenic treatment was found to increase the volume fraction of the MC carbide by up to 10% compared to the conventional heat treatment (CHT) condition in the SCT region (both 12 and 36 h) and DCT with 12 h holding time. Due to the microstructure modification, it was found that the cryogenic treatment can improve material hardness and lead to an increase in the wear resistance of SKH51 by up to 70% compared to the CHT treated material. This was due to the increase in the compressive residual stress, precipitation of the MC, and growth of the M6C primary carbide.

Application of Advanced Experimental Techniques for the Microstructural Characterization of Nanobainitic Steels

2011 ◽  
Vol 172-174 ◽  
pp. 1249-1254 ◽  
Author(s):  
Ilana Timokhina ◽  
Hossein Beladi ◽  
Xiang Yuan Xiong ◽  
Yoshitaka Adachi ◽  
Peter D. Hodgson
Keyword(s):  
Dislocation Density ◽  
Carbon Content ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Accurate Determination ◽  
Bainitic Ferrite ◽  
Microstructural Characterization ◽  
Atom Probe ◽  
Isothermal Heat Treatment ◽  
Local Composition

A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 350°C bainitic transformation temperature for 1 day to form fully bainitic structure with nano-layers of bainitic ferrite and retained austenite, while a 0.26C-1.96Si-2Mn-0.31Mo (wt%) steel was subjected to a successive isothermal heat treatment at 700°C for 300 min followed by 350°C for 120 min to form a hybrid microstructure consisting of ductile ferrite and fine scale bainite. The dislocation density and morphology of bainitic ferrite, and retained austenite characteristics such as size, and volume fraction were studied using Transmission Electron Microscopy. It was found that bainitic ferrite has high dislocation density for both steels. The retained austenite characteristics and bainite morphology were affected by composition of steels. Atom Probe Tomography (APT) has the high spatial resolution required for accurate determination of the carbon content of the bainitic ferrite and retained austenite, the solute distribution between these phases and calculation of the local composition of fine clusters and particles that allows to provide detailed insight into the bainite transformation of the steels. The carbon content of bainitic ferrite in both steels was found to be higher compared to the para-equilibrium level of carbon in ferrite. APT also revealed the presence of fine C-rich clusters and Fe-C carbides in bainitic ferrite of both steels.

SANS Study of Carbon Addition in Ti–45Al–5Nb

2011 ◽  
Vol 1295 ◽  
Author(s):  
P. Staron ◽  
F.-P. Schimansky ◽  
C. Scheu ◽  
H. Clemens
Keyword(s):  
Neutron Scattering ◽  
Size Distribution ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Tial Alloy ◽  
Small Volume ◽  
Volume Fraction ◽  
Atom Probe ◽  
Carbon Addition ◽  
Small Volume Fraction

ABSTRACTThe distribution of carbon in Ti–45Al–5Nb–0.5C was studied using small-angle neutron scattering (SANS). In an earlier study, carbon had been found to form small perovskite precipitates in a γ-TiAl alloy without Nb, which significantly increase the strength of the material. In the Nb-containing alloy, however, no strengthening precipitates were observed, but most of the C was found to be homogeneously distributed. Atom probe investigations revealed only few C-enriched regions. The present SANS investigation was carried out to confirm the presence and size distribution of these C-enriched regions in the material. The SANS results show that a small volume fraction of such C-enriched regions is present, while the large number of small precipitates found in the alloy without Nb is indeed missing in the Nb-containing alloy.

scholarly journals Influence of Deep Cryogenic Treatment on Microstructure and Properties of 7A99 Ultra-High Strength Aluminum Alloy

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 631 ◽  
Author(s):  
Wenlin Gao ◽  
Xiangjie Wang ◽  
Junzhou Chen ◽  
Chunyan Ban ◽  
Jianzhong Cui ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Electron Backscatter Diffraction ◽  
Fatigue Behavior ◽  
Cryogenic Treatment ◽  
Aging Treatment ◽  
High Strength ◽  
Atom Probe ◽  
Homogeneous Distribution ◽  
Deep Cryogenic Treatment ◽  
High Strength Aluminum Alloy

The hardness, toughness, wear resistance, and fatigue behavior of materials can be improved through a deep cryogenic treatment (DCT). During this treatment, low temperatures (−100 °C to −196 °C) are maintained and then increased to room or higher. In this work, an indirect-extrusion plate of 7A99 ultra-high strength aluminum alloy was subjected to a T6 (peak aging) treatment and a T6-DCT treatment. The influence of the T6-DCT treatment on the mechanical properties, grain morphologies, precipitates, and atom–cluster distribution was investigated via tensile testing, electron backscatter diffraction, transmission electron microscopy, and three-dimensional atom probe analysis. The tensile strength (maximum: 705 deep cryogenic treatment), yield strength (maximum: 678 MPa), and elongation (maximum: 14%) of the T6-DCT-treated alloy were higher than those of the T6-treated alloy. Moreover, the T6-DCT treatment resulted in (i) grain size refinement and increased uniformity of the microstructure (homogeneous distribution of η’-MgZn2- and η-phase precipitates), and (ii) reduced segregation degree of Zn, Mg, and Cu atoms in the matrix (fraction of small atom clusters (sizes: 10–20 nm, 20–50 nm) increased, fraction of large clusters (size: >1,000 nm) decreased). Therefore, DCT can refine the precipitates and increase the uniformity of the precipitate distribution, thereby improving the strength and plasticity of the alloy.

scholarly journals Effect of Alloying on the Nucleation and Growth of Laves Phase in the 9–10%Cr-3%Co Martensitic Steels during Creep

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 60
Author(s):  
Alexandra Fedoseeva ◽  
Ivan Nikitin ◽  
Evgeniy Tkachev ◽  
Roman Mishnev ◽  
Nadezhda Dudova ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Laves Phase ◽  
High Rate ◽  
Initial Stresses ◽  
Martensitic Steels ◽  
Creep Tests ◽  
Nucleation Sites ◽  
Mo Content ◽  
M23c6 Carbides

Five Co-modified P92-type steels with different contents of Cr, W, Mo, B, N, and Re have been examined to evaluate the effect of the chemical composition on the evolution of Laves phase during creep at 650 °C. The creep tests have been carried out at 650 °C under various applied initial stresses ranging from 80 to 200 MPa until rupture. An increase in the B and Cr contents leads to a decrease in the size and volume fraction of M23C6 carbides precipitated during tempering and an increase in their number particle density along the boundaries. In turns, this affects the amount of the nucleation sites for Laves phase during creep. The (W+Mo) content determines the diffusion growth and coarsening of Laves phase during creep. Susceptibility of Laves phase to coarsening with a high rate is caused by the large difference in Gibbs energy between fine and large particles located at the low-angle and high-angle boundaries, respectively, and can cause the creep strength breakdown. The addition of Re to the 10%Cr steel with low N and high B contents provides the slowest coarsening of Laves phase among the steels studied.

scholarly journals Critical Consideration of Precipitate Analysis of Fe–1 at.% Cu Using Atom Probe and Small-Angle Neutron Scattering

2010 ◽  
Vol 17 (1) ◽  
pp. 26-33 ◽  
Author(s):  
M. Schober ◽  
E. Eidenberger ◽  
P. Staron ◽  
H. Leitner
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Volume Fraction ◽  
Search Algorithm ◽  
Atom Probe ◽  
Magnetic Scattering ◽  
Model Alloy ◽  
Chemical Compositions ◽  
Heat Treated

AbstractAn Fe–1 at.% Cu model alloy was examined by atom probe (3DAP) and small-angle neutron scattering (SANS) to verify the accordance of the gained results. The Fe-Cu alloy was heat-treated for various times at 500°C, forming Cu-rich precipitates within the Fe matrix. The chemical compositions of the precipitates and matrix found by 3DAP were used to calculate the magnetic scattering contrast. Additionally, a magnetic moment of the precipitates that contain a significant amount of Fe was taken into account for the calculation of magnetic scattering contrast. This in turn is used for the evaluation of the magnetic scattering curves gained by SANS. Both the 3DAP data as well as the scattering curves were analyzed with regard to radius, number density, and volume fraction of the precipitates as a function of aging time. The results yielded by both techniques are in good agreement and correspond to the development of the hardness of the alloy. Minor differences can be related to the cluster search algorithm used for the analysis of the 3DAP data as well as Fe overestimation based on different field phases.

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