开发具有优异综合性能的核反应堆结构材料是核能发展的基础,并且是长期以来制约核能推广的难点之一。多主元合金(multiprincipal element alloys,MEAs)因具有良好的抗辐照性能、力学性能而被认为是先进反应堆结构材料的候选材料,为新型...开发具有优异综合性能的核反应堆结构材料是核能发展的基础,并且是长期以来制约核能推广的难点之一。多主元合金(multiprincipal element alloys,MEAs)因具有良好的抗辐照性能、力学性能而被认为是先进反应堆结构材料的候选材料,为新型抗辐照材料的设计开辟了广阔空间。近年来,有关多主元合金在辐照损伤方面的研究多试图揭示多主元合金一些因素和特性对辐照过程中缺陷形成与演变的影响。例如:主元种类和数目、主元浓度、晶格畸变、化学短程序等。尽管现有的一些研究结果表明以上因素可以提高多主元合金抗辐照损伤能力,但是在不同辐照条件下,以上因素对多主元合金中缺陷形成和演变的影响机制存在较大差异,难以得出普适性的结论。本文围绕FCC和BCC系两类多主元合金的辐照肿胀、氦泡形成、辐照诱导元素偏析和相变、辐照硬化四方面内容,综述了近年来多主元合金在辐照损伤方面的研究进展,总结了多主元合金提高抗辐照性能的作用机制,并在此基础上对核电结构用多主元合金的未来研究方向做出了展望,包括短程序调控、高熵陶瓷、增材制造、高通量结合机器学习加速材料开发等。最后指出必须从合金成分设计的角度出发,基于材料服役的实际环境来设计新型抗辐照多主元合金。展开更多
Metals heat-treated under high pressure can exhibit different properties. The heat-induced pressure on 2024 aluminum alloy during restricting expansion-deformation heat-treatment was calculated by using the ABAQUS fin...Metals heat-treated under high pressure can exhibit different properties. The heat-induced pressure on 2024 aluminum alloy during restricting expansion-deformation heat-treatment was calculated by using the ABAQUS finite element software, and the effects of the mould material properties, such as coefficient of thermal expansion （CTE）, elastic modulus and yield strength, on the pressure were discussed. The simulated results show that the relatively uniform heat-induced pressure, approximately 503 MPa at 500 ℃, appears on 2024 alloy when 42CrMo steel is as the mould material. The heat-induced pressure increases with decreasing the CTE and the increases of elastic modulus and yield strength of the mould material. The influences of the CTE and elastic modulus on the heat-induced pressure are more notable.展开更多
The flow behavior of Rene 95 PM alloy was studied from 1050 to 1150 deg Cwith strain rate of 1 X 10^(-3), 1 X 10^(-2), 1 X 10^(-1) and 1 s^(-1). At a given temperature andstrain rate, flow curves exhibit a peak follow...The flow behavior of Rene 95 PM alloy was studied from 1050 to 1150 deg Cwith strain rate of 1 X 10^(-3), 1 X 10^(-2), 1 X 10^(-1) and 1 s^(-1). At a given temperature andstrain rate, flow curves exhibit a peak followed by flow softening up to a steady state. Moreover,at constant strain, flow stress increases with increasing strain rate and decreasing temperature. Anequation relating hyperbolic sine of flow stress to hot working parameters, such as strain, strainrate and temperature, was established by using multiple nonlinear regression method. A very goodagreement was found between predicted and experimental flow stress in all the strain rangeinvestigated. Application of the constitutive equation in predicting forming loads and flow behaviorand temperature distribution in both upper and lower dies in an isothermal forging process ofturbine disk of large dimension (about 630 mm) by means of a finite element code was systematicallyanalyzed.展开更多
The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, ther...The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, there are problems such as high cutting force, poor surface integrity, and high cutting temperature during conventional machining. As an advanced processing method with high efciency and low damage, laser-assisted machining can improve the machinability of titanium alloy. In this study, a picosecond pulse laser-assisted scratching (PPLAS) method considering both the temperature-dependent material properties and ultrashort pulse laser’s characteristics is frst proposed. Then, the efects of laser power, scratching depth, and scratching speed on the distribution of stress and temperature feld are investigated by simulation. Next, PPLAS experiments are conducted to verify the correctness of the simulation and reveal the removal behavior at various combinations of laser power and scratching depths. Finally, combined with simulated and experimental results, the removal mechanism under the two machining methods is illustrated. Compared with conventional scratching (CS), the tangential grinding force is reduced by more than 60% and the material removal degree is up to 0.948 during PPLAS, while the material removal is still primarily in the form of plastic removal. Grinding debris in CS takes the form of stacked fakes with a “fsh scale” surface, whereas it takes the form of broken serrations in PPLAS. This research can provide important guidance for titanium alloy grinding with high surface quality and low surface damage.展开更多
The possibility of the electric-hydraulic chattering technology and its application in the cold extrusion were presented.The conventional and electric-hydraulic chattering assisted backward extrusion processes were pe...The possibility of the electric-hydraulic chattering technology and its application in the cold extrusion were presented.The conventional and electric-hydraulic chattering assisted backward extrusion processes were performed on 6061 aluminum alloy billets at room temperature.The experimental results showed that 5.65% reduction in the extrusion load was attained if the die and ejector were vibrated at a frequency of 100 Hz and amplitude of 0.013 mm in the longitudinal direction.The friction coefficient at the billet and tool system interface determined from the finite element analysis（FEA） decreased from 0.2 without chattering to 0.1 with application of electric-hydraulic chattering.The higher values of instantaneous velocity and direction change of material flow were achieved during the chattering assisted backward extrusion process.The strain distribution of the chattering assisted backward extrusion billet revealed lower maximum strain and smoother strain distribution in comparison with that produced by the conventional extrusion method.展开更多
文摘开发具有优异综合性能的核反应堆结构材料是核能发展的基础,并且是长期以来制约核能推广的难点之一。多主元合金(multiprincipal element alloys,MEAs)因具有良好的抗辐照性能、力学性能而被认为是先进反应堆结构材料的候选材料,为新型抗辐照材料的设计开辟了广阔空间。近年来,有关多主元合金在辐照损伤方面的研究多试图揭示多主元合金一些因素和特性对辐照过程中缺陷形成与演变的影响。例如:主元种类和数目、主元浓度、晶格畸变、化学短程序等。尽管现有的一些研究结果表明以上因素可以提高多主元合金抗辐照损伤能力,但是在不同辐照条件下,以上因素对多主元合金中缺陷形成和演变的影响机制存在较大差异,难以得出普适性的结论。本文围绕FCC和BCC系两类多主元合金的辐照肿胀、氦泡形成、辐照诱导元素偏析和相变、辐照硬化四方面内容,综述了近年来多主元合金在辐照损伤方面的研究进展,总结了多主元合金提高抗辐照性能的作用机制,并在此基础上对核电结构用多主元合金的未来研究方向做出了展望,包括短程序调控、高熵陶瓷、增材制造、高通量结合机器学习加速材料开发等。最后指出必须从合金成分设计的角度出发,基于材料服役的实际环境来设计新型抗辐照多主元合金。
基金Project (51071125) supported by the National Natural Science Foundation of ChinaProjects (SKLSP201107, SKLSP 201124) supported by the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University, China
文摘Metals heat-treated under high pressure can exhibit different properties. The heat-induced pressure on 2024 aluminum alloy during restricting expansion-deformation heat-treatment was calculated by using the ABAQUS finite element software, and the effects of the mould material properties, such as coefficient of thermal expansion （CTE）, elastic modulus and yield strength, on the pressure were discussed. The simulated results show that the relatively uniform heat-induced pressure, approximately 503 MPa at 500 ℃, appears on 2024 alloy when 42CrMo steel is as the mould material. The heat-induced pressure increases with decreasing the CTE and the increases of elastic modulus and yield strength of the mould material. The influences of the CTE and elastic modulus on the heat-induced pressure are more notable.
文摘The flow behavior of Rene 95 PM alloy was studied from 1050 to 1150 deg Cwith strain rate of 1 X 10^(-3), 1 X 10^(-2), 1 X 10^(-1) and 1 s^(-1). At a given temperature andstrain rate, flow curves exhibit a peak followed by flow softening up to a steady state. Moreover,at constant strain, flow stress increases with increasing strain rate and decreasing temperature. Anequation relating hyperbolic sine of flow stress to hot working parameters, such as strain, strainrate and temperature, was established by using multiple nonlinear regression method. A very goodagreement was found between predicted and experimental flow stress in all the strain rangeinvestigated. Application of the constitutive equation in predicting forming loads and flow behaviorand temperature distribution in both upper and lower dies in an isothermal forging process ofturbine disk of large dimension (about 630 mm) by means of a finite element code was systematicallyanalyzed.
基金the financial support provided by the National Natural Science Foundation of China(No.52274369)the China Postdoctoral Science Foundation(No.2018M632986)+2 种基金the Natural Science Foundation of Hunan Province,China(No.2019JJ50766)the Postdoctoral Science Foundation of Central South University,Chinathe Science and Technology Program of Hunan,China(No.2020GK2044)。
基金Supported by National Natural Science Foundation of China(Grant No.52175377)Chongqing Municipal Science Foundation(Grant No.CSTB2022NSCQ-LZX0080)+1 种基金Fundamental Research Funds for Central Universities(Grant Nos.2023CDJXY-026 and 2023CDJXY-021)National Science and Technology Major Project(Grant No.2017-VII-0002-0095).
文摘The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, there are problems such as high cutting force, poor surface integrity, and high cutting temperature during conventional machining. As an advanced processing method with high efciency and low damage, laser-assisted machining can improve the machinability of titanium alloy. In this study, a picosecond pulse laser-assisted scratching (PPLAS) method considering both the temperature-dependent material properties and ultrashort pulse laser’s characteristics is frst proposed. Then, the efects of laser power, scratching depth, and scratching speed on the distribution of stress and temperature feld are investigated by simulation. Next, PPLAS experiments are conducted to verify the correctness of the simulation and reveal the removal behavior at various combinations of laser power and scratching depths. Finally, combined with simulated and experimental results, the removal mechanism under the two machining methods is illustrated. Compared with conventional scratching (CS), the tangential grinding force is reduced by more than 60% and the material removal degree is up to 0.948 during PPLAS, while the material removal is still primarily in the form of plastic removal. Grinding debris in CS takes the form of stacked fakes with a “fsh scale” surface, whereas it takes the form of broken serrations in PPLAS. This research can provide important guidance for titanium alloy grinding with high surface quality and low surface damage.
基金Project(51275475)supported by the National Natural Science Foundation of ChinaProject(2014BY001)supported by the Department of Education in Zhejiang Province,ChinaProject(2014EP0110)supported by the Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology,Ministry of Education and Zhejiang Province,China
文摘The possibility of the electric-hydraulic chattering technology and its application in the cold extrusion were presented.The conventional and electric-hydraulic chattering assisted backward extrusion processes were performed on 6061 aluminum alloy billets at room temperature.The experimental results showed that 5.65% reduction in the extrusion load was attained if the die and ejector were vibrated at a frequency of 100 Hz and amplitude of 0.013 mm in the longitudinal direction.The friction coefficient at the billet and tool system interface determined from the finite element analysis（FEA） decreased from 0.2 without chattering to 0.1 with application of electric-hydraulic chattering.The higher values of instantaneous velocity and direction change of material flow were achieved during the chattering assisted backward extrusion process.The strain distribution of the chattering assisted backward extrusion billet revealed lower maximum strain and smoother strain distribution in comparison with that produced by the conventional extrusion method.
