The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Q F Fang - One of the best experts on this subject based on the ideXlab platform.
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determination of the dbtt of nanoscale zrc doped w alloys through amplitude dependent internal friction technique
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: H.l. Ding, T. Zhang, Z M Xie, Q F Fang, Zhijun Cheng, Zhong Zhuang, Xianping Wang, Congliang LiuAbstract:Abstract In this paper, 1 mm thick W-0.5 wt%ZrC alloy plates were prepared by mechanical milling, hot pressing sintering and multistep hot and cold rolling. A newly developed testing technique based on the amplitude-dependent internal friction (ADIF) was used to determine the Ductile-to-Brittle Transition Temperature (DBTT) of this W-0.5 wt%ZrC alloy. The DBTT obtained by ADIF technique is in the range of 50–80 °C, which is in consistence with the tensile tests. Qualitative relationship between the critical strain amplitude in ADIF and the yield stress in tensile test was also found. The ADIF technique was confirmed to be an available method to determine the DBTT of the materials. Microstructure analysis indicated that the relative low DBTT and the high strength of the W-0.5 wt%ZrC alloy plates were resulted from the multistep hot and cold rolling and nanoscale particle pinning effects.
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extraordinary high ductility strength of the interface designed bulk w zrc alloy plate at relatively low Temperature
Scientific Reports, 2015Co-Authors: T. Zhang, Q F Fang, Shiding Miao, X D Yang, X P WangAbstract:The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room Temperature (RT) and Ductile-to-Brittle Transition Temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength.
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microstructure and mechanical properties of nano size zirconium carbide dispersion strengthened tungsten alloys fabricated by spark plasma sintering method
Plasma Science & Technology, 2015Co-Authors: Q F Fang, Tao Zhang, Yan Jiang, Xianping WangAbstract:W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room Temperature, higher tensile strength at high Temperature, and a lower ductile to brittle Transition Temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C–600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.
Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.
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effect of grain refinement to 1 μm on strength and toughness of dual phase steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Marion Calcagnotto, Dirk Ponge, Dierk RaabeAbstract:Large strain warm deformation at different Temperatures and subsequent intercritical annealing has been applied to obtain fine grained (2.4m) and ultrafine grained (1.2m) ferrite/martensite dual-phase (DP) steels. Their mechanical properties were tested under tensile and impact conditions and compared to a hot deformed coarse grained (12.4m) reference material. Both yield strength and tensile strength follow a Hall–Petch type linear relationship, whereas uniform elongation and total elongation are hardly affected by grain refinement. The initial strain hardening rate as well as the post-uniform elongation increase with decreasing grain size. Ductile fracture mechanisms are considerably promoted due to grain refinement. Grain refinement further lowers the Ductile-to-Brittle Transition Temperature and leads to higher absorbed impact energies. Besides the common correlations with the ferrite grain size, these phenomena are explained in terms of the martensite particle size, shape and distribution and the more homogeneous dislocation distribution in ultrafine ferrite grains.
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mechanical properties of an ultrafine grained c mn steel processed by warm deformation and annealing
Acta Materialia, 2005Co-Authors: R Song, Dirk Ponge, Dierk RaabeAbstract:Abstract The mechanical properties of an ultrafine grained 0.2%C–Mn steel, processed by large strain warm deformation and subsequent annealing, have been investigated. The microstructure consists of spheroidized cementite particles in an ultrafine ferrite matrix (average grain diameter ≈1.3 μm). The steel shows an improved combination of strength and toughness when compared with corresponding coarse grained specimens. The reasonable ductility of the steel can be attributed to the finely dispersed cementite particles, which also effectively increase the work hardening rate by the accumulation of geometrically necessary dislocations in their vicinity. The lower shelf energy is significantly higher and the Ductile-to-Brittle Transition Temperature is lower in the ultrafine grained steel than in comparable coarse grained specimens. This may be due to the joint effect of grain refinement and delamination in the ultrafine grained steel processed by large strain deformation. The delaminations lead to a decrease in triaxiality of the stress state in the impact test samples. The upper shelf energy is slightly reduced in the ultrafine grained steel, which can be attributed to the effect of delamination.
Petr Hausild - One of the best experts on this subject based on the ideXlab platform.
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prediction of cleavage fracture for a low alloy steel in the ductile to brittle Transition Temperature range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Clotilde Berdin, Petr Hausild, Philippe BompardAbstract:This paper attempts to predict the cleavage fracture probability for a low-alloy bainitic steel. Fractographic analysis of broken compact tension (CT) and Charpy V-notch (CVN) specimens was performed. An evolution of physical mechanisms of cleavage initiation was found: cracked-particle-induced cleavage was observed at low Temperature, whereas a plasticity-induced mechanism was assumed as Temperature increases. To take into account these observations, Temperature-dependent Weibull parameters were used in the Beremin model. The introduction of a threshold cleavage stress was necessary to account for the skewness of the fracture probability distribution. With these parameters identified on the instrumented Charpy data set, the fracture toughness Jc was successfully predicted in the DBTT range.
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the influence of ductile tearing on fracture energy in the ductile to brittle Transition Temperature range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002Co-Authors: Petr Hausild, Clotilde Berdin, Ivan Nedbal, C PrioulAbstract:The aim of this study is to examine the relationship between fracture energy and the ductile area measured on the fracture surface. Instrumented Charpy tests and fracture toughness tests are performed in the Transition Temperature range, as well as at lower Temperatures. Quantitative fractographic analyses of Charpy specimens reveal a certain proportion of ductile fracture even if the Charpy test is conducted at low Temperatures, below the Transition Temperature. The ductile fracture area situated next to the notch is correlated to fracture energy for all Temperatures. In the Transition Temperature range, fracture energy and the ductile area have a large scatter. Since the limiting event in the development of the ductile area is the initiation of cleavage, the maximum principal stress has been computed in different specimens using the finite element method. It has been shown that the propagating ductile crack does not increase the stress level, but does increase the probability of cleavage fracture through an expansion of the plastic volume where weak points can be found.
Amir Ali Milani - One of the best experts on this subject based on the ideXlab platform.
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Modeling ductile to brittle Transition Temperature of functionally graded steels by fuzzy logic
Journal of Materials Science, 2011Co-Authors: Ali Nazari, Amir Ali MilaniAbstract:In this article, a model based on fuzzy logic (FL) for predicting ductile to brittle Transition Temperature of functionally graded steels in both crack divider and crack arrester configurations has been presented. Functionally graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced by electroslag remelting. For purpose of building the model, training and testing using experimental results from 140 specimens produced from two basic composites were conducted. The used data as inputs in FL models are arranged in a format of six input parameters that cover the FGS type, the crack tip configuration, the thickness of graded ferritic region, the thickness of graded austenitic region, the distance of the notch from bainite or martensite intermediate layer, and Temperature. According to these input parameters, in the FL, the ductile to brittle Transition Temperature of each FGS specimen was predicted. It has been found that FL model will be valid within the ranges of variables. The training and testing results in the FL model have shown a strong potential for predicting the ductile to brittle Transition Temperature of each FGS specimen.
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Modeling Ductile-to-Brittle Transition Temperature of Functionally Graded Steels by Gene Expression Programming
International Journal of Damage Mechanics, 2011Co-Authors: Amir Ali Milani, Ali NazariAbstract:In this article, a model based on gene expression programming for pre- dicting Ductile-to-Brittle Transition Temperature of functionally graded steels in both crack divider and crack arrester configurations has been presented. Functionally, graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced by electroslag remelting. For the purpose of building the model, training and testing using experimental results from 140 specimens produced from two basic composites were conducted. The data used as input in gene expression programming models are arranged in a format of six parameters that cover the FGS type, the crack tip configuration, the thickness of graded ferritic region, the thickness of graded austenitic region, the distance of the notch from bainite or martensite intermediate layer, and Temperature. According to these input parameters, in the gene expression programming, the Ductile-to-Brittle Transition Temperature of each FGS specimen was predicted. The training and testing results in the gene expression programming model have shown strong potential for predicting the Ductile-to-Brittle Transition Temperature of each FGS specimens.
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Modeling ductile to brittle Transition Temperature of functionally graded steels by artificial neural networks
Computational Materials Science, 2011Co-Authors: Ali Nazari, Amir Ali Milani, Mahnaz ZakeriAbstract:In the present paper, a model based on artificial neural networks for predicting ductile to brittle Transition Temperature of functionally graded steels in both crack divider and crack arrester configurations has been presented. Functionally graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced by electroslag remelting. To build the model, training and testing were conducted using experimental results from 140 specimens produced of two basic composites. The utilized data in the multilayer feed forward neural networks models are arranged in a format of six input parameters that cover the specimen type, the crack tip configuration, the thickness of graded ferritic region, the thickness of graded austenitic region, the distance of the notch from bainite or martensite intermediate layer and Temperature. According to these input parameters, in the neural networks models, the ductile to brittle Transition Temperature of each specimen was predicted. The training and testing results in the neural network model have shown a strong potential for predicting the ductile to brittle Transition Temperature of each specimen.
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ductile to brittle Transition Temperature of functionally graded steels with crack arrester configuration
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Ali Nazari, Amir Ali MilaniAbstract:Abstract In the present study, ductile to brittle Transition Temperature of functionally graded steels has been evaluated by utilizing Charpy impact specimens with crack arrester configuration. Functionally graded steels which are composed of graded ferritic and austenitic regions together with bainite or martensite layer may be fabricated by electroslag remelting. For the specimens with the notches tip placed at graded ferritic region, the closer the notch tip to the bainite layer, the lower the Transition Temperature. For the specimens with the notches tip placed at graded austenitic region, no Transition Temperature was observed. It has been found that by situating a crack at bainite–ferrite while it propagates into graded austenitic region, no Transition Temperature is observed. On the other hand, a crack situated at austenite–bainite interface propagating into graded ferritic region experiences Transition Temperature.
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Ductile to Brittle Transition Temperature of Functionally Graded Steels
International Journal of Damage Mechanics, 2011Co-Authors: Ali Nazari, Amir Ali MilaniAbstract:In this study, Ductile-to-Brittle Transition Temperature of functionally graded steels produced by electroslag remelting in both crack divider and crack arrester configurations has been investigated. In crack divider configuration, the results indicate that the brittle behavior depends on the containing phase where brittleness of a specific phase in a certain Temperature plays the main role in the fracture of the specimen. In crack arrester configuration, for the specimens with the notch tip placed at graded ferritic region, the closer the notch tip to the bainite layer, the lower the Transition Temperature. For the specimens with the notch tip placed at graded austenitic region, no Transition Temperature was observed. It has been found that by situating a crack at bainiteferrite while it propagates into graded austenitic region, no Transition Temperature is observed. On the other hand, a crack situated at austenitebainite interface propagating into graded ferritic region experiences tran- sition Temperature.
T. Zhang - One of the best experts on this subject based on the ideXlab platform.
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determination of the dbtt of nanoscale zrc doped w alloys through amplitude dependent internal friction technique
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: H.l. Ding, T. Zhang, Z M Xie, Q F Fang, Zhijun Cheng, Zhong Zhuang, Xianping Wang, Congliang LiuAbstract:Abstract In this paper, 1 mm thick W-0.5 wt%ZrC alloy plates were prepared by mechanical milling, hot pressing sintering and multistep hot and cold rolling. A newly developed testing technique based on the amplitude-dependent internal friction (ADIF) was used to determine the Ductile-to-Brittle Transition Temperature (DBTT) of this W-0.5 wt%ZrC alloy. The DBTT obtained by ADIF technique is in the range of 50–80 °C, which is in consistence with the tensile tests. Qualitative relationship between the critical strain amplitude in ADIF and the yield stress in tensile test was also found. The ADIF technique was confirmed to be an available method to determine the DBTT of the materials. Microstructure analysis indicated that the relative low DBTT and the high strength of the W-0.5 wt%ZrC alloy plates were resulted from the multistep hot and cold rolling and nanoscale particle pinning effects.
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Nondestructive Evaluation of Ductile to Brittle Transition Temperature for Martensitic Steels Based on Magnetic Measurements
Journal of Nondestructive Evaluation, 2017Co-Authors: H.l. Ding, T. Zhang, Qi-wu Fang, R. Gao, Xuejiang Wang, C.s. LiuAbstract:Interest in magnetic nondestructive evaluation (NDE) methods for nuclear reactors materials to quantify material embrittlement and ensure reactor safety is increased. In this paper, ductile–brittle Transition Temperature (DBTT) and Temperature dependence of the coercive field (\(H_{C})\) and magnetization (M) of martensitic steels (F82H, Eurofer97, SCRAM, T91 and cold rolled T91 steels) were investigated from 100 to 350 K to non-destructively evaluate their DBTT. Results show that a characteristic Temperature in both ln(\(H_{C})\) and d(lnM)/d(1/T) vs Temperature curves coincides well with the corresponding DBTT measured by Charpy impact test. The curves decrease linearly above and below DBTT respectively, the absolute slope above DBTT is larger than that below. The phenomenon is closely related to the different motion status and the pinning strength of dislocations and magnetic domain wall in the ductile and brittle regions. Results indicate the magnetic evaluation method could be a promising technique with good reproducibility and high sensitivity to evaluate DBTT of martensitic steels used in nuclear reactors.
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extraordinary high ductility strength of the interface designed bulk w zrc alloy plate at relatively low Temperature
Scientific Reports, 2015Co-Authors: T. Zhang, Q F Fang, Shiding Miao, X D Yang, X P WangAbstract:The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room Temperature (RT) and Ductile-to-Brittle Transition Temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength.
