National Key Laboratory for Precision Hot Processing of Metals

Harbin, China

National Key Laboratory for Precision Hot Processing of Metals

Harbin, China
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Yuan L.,Harbin Institute of Technology | Yuan L.,National Key Laboratory for Precision Hot Processing of Metals | Shi W.,Harbin Institute of Technology | Shi W.,National Key Laboratory for Precision Hot Processing of Metals | And 5 more authors.
Journal of Materials Processing Technology | Year: 2017

Whisker reinforced aluminum alloy composites are attractive for structural applications in automotive and aerospace applications. However, their forgeability is limited by their poor ductility at room temperature. The effects of temperatures (350–520 °C) and strain rates (0.01–50 s−1) on the resistance to microcracking and on the closure of voids are investigated for 2024Al/Al18B4O33w whisker composite as well as unreinforced AA2024 alloy. Under elevated temperature and high strain rate (>450 °C, >1.0 s−1), there are less cracks and no axial splitting on the surface of 2024Al/Al18B4O33w composite. Test results show lower flow stresses and incipient melting at higher temperatures enable better tolerance of whisker-matrix strain mismatch at the interface during hot compression resulting in increased stabilization of flow stresses. While higher strain rates contribute to increased strain rate hardening, whisker rotation and void closure. It is interesting to note that the unreinforced AA2024 alloy experiences flow localization, surface cracking and plastic instability at temperatures higher than 450 °C but the presence of Al18B4O33 in the composite seems to better resist these failure mechanisms resulting in higher forgeability. © 2017 Elsevier B.V.


Yuan L.,Harbin Institute of Technology | Yuan L.,National Key Laboratory for Precision Hot Processing of Metals | Jing P.,Harbin Institute of Technology | Jing P.,National Key Laboratory for Precision Hot Processing of Metals | And 4 more authors.
Applied Surface Science | Year: 2017

Atomistic simulations were used to investigate the plastic deformation behavior of bicrystalline silver nanowires with Σ3 asymmetric tilt grain boundaries at 0.1 K. The calculated grain boundary energies of Σ3 asymmetric tilt grain boundaries corresponded well with the energies measured in experiments and predicted by the theoretical description. The Σ3 asymmetric tilt grain boundaries with low inclination angles were composed of a replication of twin boundary segments separated by small ledges. The results demonstrated that the combination effect of Schmid factor and non-Schmid factors could explain dislocations emission into grain 1 only in models with low inclination angles (Ф < 64.76°). At the latter stage of plastic deformation, free surfaces served as additional dislocation sources. Parallelly arranged operative slip systems were the fundamental features of plastic deformation. In addition, a number of stacking faults and multiple stacking faults were formed during plastic deformation. The hindrance of stacking faults to dislocation motion and the interactions between dislocations leaded to the observed strain hardening in nanowires with inclination angles at and above 29.50°. The low stacking fault energy of silver was responsible for the appearance of strain hardening. Dislocations emitted from grain 2 interacted with each other contributing to the observed strain hardening. Grain boundaries were completely eliminated by successive emission of dislocations from grain boundaries in nanowires with an inclination angle of 35.26° and 54.74°. A detailed understanding of the relationship between strength and grain boundary structures as well as specific plastic deformation would push forward the application of nanocrystalline materials and provide insights into the synthesis of nanocrystalline materials with superior strength and ductility. © 2016 Elsevier B.V.


Wang C.J.,National Key Laboratory for Precision Hot Processing of Metals | Wang C.J.,Harbin Institute of Technology | Liu Y.,Harbin Institute of Technology | Guo B.,National Key Laboratory for Precision Hot Processing of Metals | And 4 more authors.
Materials and Design | Year: 2016

Ultrasonic vibration is widely utilized in manufacturing processes mainly because acoustic field could significantly affect the metal plasticity leading to stress reduction. However, viewpoints on the influence mechanism have not reached a consensus yet. In this paper, an ultrasonic vibration assisted uniaxial tension experiment with copper foils is carried out using a specially-developed device. The results show that the extent of stress reduction increases with the increase of the vibration amplitude. Acoustic softening and stress superposition are both considered in a developed model to describe the stress reduction due to ultrasonic excitation during metal forming process. Considering that ultrasonic vibration provides the energy for dislocation sliding, acoustic softening is analyzed based on crystal plasticity theory considering ultrasonic intensity. Stress superposition, mostly induced by the additional periodic strain, is included by taking account of its proportional relationship with vibration amplitude. The calculation results from the numerical model show a good agreement with those from the experiment. These findings provide an instructive understanding of mechanism of stress reduction in ultrasonic vibration assisted metal deformation and are especially helpful for pro-actively designing ultrasonic vibration assisted metal forming processes. © 2016 Elsevier Ltd


Liu G.,National Key Laboratory for Precision Hot Processing of Metals | Liu G.,Harbin Institute of Technology | Wang J.,National Key Laboratory for Precision Hot Processing of Metals | Tang Z.,Nanjing University of Aeronautics and Astronautics | Wu Y.,National Key Laboratory for Precision Hot Processing of Metals
Key Engineering Materials | Year: 2014

A process with gas pressure up to 70MPa is introduced, which is called High Pressure Pneumatic Forming (HPPF), comparing to superplastic forming (SPF) with pressure lower than 5MPa. HPPF process can be used to form tube blank at lower temperature with high energy efficiency and also at higher strain rate than SPF. With Ti-3Al-2.5V Ti-alloy tube, the potential of HPPF was studied through experiment in the temperature range of 700~850?. To know the formability of the Ti-alloy tube, HPPF experiments of a large expansion tube and a square cross-section tube were carried out at different temperature and pressure. The limit expansion ratio and limit radius were measured to evaluate the forming limit of Ti-3Al-2.5V tube within HPPF. The results show that the lower the pressure, the better formability and the lower efficiency. At a constant pressure, the strain rate increases exponentially with bulging time during the free bulging procedure, but decreases exponentially during the small corner calibration. Through EBSD pictures, the deformation mechanism of the corner forming process in HPPF was analyzed. Because of a nonconstant strain rate deformation state and complicated stress and strain state during HPPF, the microstructure at the transition zone of the components are also nonhomogenous, but the grains are refined to a certain extent. © (2014) Trans Tech Publications, Switzerland.


Fan Z.,Harbin Institute of Technology | Yu H.,Harbin Institute of Technology | Yu H.,National Key Laboratory for Precision Hot Processing of Metals | Meng F.,Harbin Institute of Technology | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015

Magnetic pulse cladding (MPC), a new technology, is proposed in this study to fabricate often utilized bi-metal tubing in engineering applications with an outer tubular component consisting of structurally strong material and an inner tubular layer of corrosion-resistant material. The MPC process includes an innovative feature that allows the outer and inner tubes to electromagnetically bond together by a sequential expansion process to form a mechanical bond between the tubes at the interface. The MPC process was experimentally arranged to produce an Al/Fe bi-metal tube with an outer carbon steel tube and an internal aluminum tube. A mechanical test was then applied to characterize bonding strength of the Al/Fe bi-metal tube. Significant process parameters including discharging voltage, radial gap, and feeding length were identified based on bonding strength influence. Overall feasibility was demonstrated for the MPC process in electromagnetic expansion pattern in the production of bi-metal tubing. © 2015 Springer-Verlag London


Zhang X.,Harbin Institute of Technology | Yu H.,Harbin Institute of Technology | Yu H.,National Key Laboratory for Precision Hot Processing of Metals | Li C.,Harbin Institute of Technology | Li C.,National Key Laboratory for Precision Hot Processing of Metals
Journal of Materials Processing Technology | Year: 2016

Cold heading (CH) is a fast and simple metal forming process to fabricate small-sized products for industry applications. Deformed microstructure under dynamic heading greatly influences properties of the products. The main objective of this work is to investigate the effect of the deformed microstructure on mechanical properties in the headed part. Consequently, the cold heading under magnetic pulse force was performed with 2A10 aluminum alloy bars. Microstructure and mechanical properties of the headed part were achieved to explore the relationship between microstructure distribution and mechanical properties. Microstructure observation showed that adiabatic shear bands (ASBs) were a remarkable characteristic of headed part, and caused the inhomogeneous distribution of deformation. The brittle Al2Cu phase particles precipitated in the ASBs. The hardness of ASB was significantly higher than that of other zones that attributed to the dual effects of work hardening and precipitation strengthening. Moreover, inhomogeneous microstructure distribution contributed varied mechanical properties in headed part, where the quasi-static compression yield strength (476 MPa) in its edge position was higher than that (395 MPa) in its central zone. And the specific microstructure from different regions of headed part contributed to varied tensile strain, fracture location and fracture mode. © 2015 Elsevier B.V. All rights reserved.


Wang C.,National Key Laboratory for Precision Hot Processing of Metals | Wang C.,Harbin Institute of Technology | Shan D.,National Key Laboratory for Precision Hot Processing of Metals | Shan D.,Harbin Institute of Technology | And 3 more authors.
Materials and Manufacturing Processes | Year: 2014

An isothermal microforging process is proposed to manufacture a microturbine with high aspect ratio microblade. Two schemes with circular and circular ring preforms were performed by the proposed isothermal micro forging process. A microturbine with a higher microblade is manufactured when using the circular ring preform compared to that using the circular one. Then, the mechanical property of microturbine is evaluated via the shear strength of the micro blade. The mechanical property is improved by solid solution and aging treatment. © 2014 Taylor and Francis Group, LLC.


Yu H.,National Key Laboratory for Precision Hot Processing of Metals | Yu H.,Harbin Institute of Technology | Fan Z.,Harbin Institute of Technology | Li C.,National Key Laboratory for Precision Hot Processing of Metals | Li C.,Harbin Institute of Technology
Journal of Materials Processing Technology | Year: 2014

Bi-metal tubes, which combine the advantageous properties of two different metals, are desirable in industries where corrosion resistance is important. A new cladding method named magnetic pulse cladding (MPC) was used to form bi-metal tubes. A cladding of mild steel tube by aluminum alloy (AA3003) was achieved. The effect of the geometry of the field shaper on cladding quality was investigated as well as other main process parameters, such as, feeding size, radial gap and discharge voltage. The mechanical property was evaluated by compression-shear test and a maximum strength of 79.2 MPa and an average of 29.7 MPa were attained to by the following process settings: profiled field shaper, feeding size of 12 mm, radial gap of 2.0 mm and discharge voltage of 15 kV. OM and SEM images show a smooth integral interface and a small wavy one. EDS mapping reveals the interfacial diffusion zone up to 50-μm wide. The results show that the proposed MPC process is able to form sound cladding bonds and could be applicable to a tubular clad component with a high axial length. © 2013 Elsevier B.V. All rights reserved.


Fan Z.,Harbin Institute of Technology | Yu H.,Harbin Institute of Technology | Yu H.,National Key Laboratory for Precision Hot Processing of Metals | Li C.,Harbin Institute of Technology | Li C.,National Key Laboratory for Precision Hot Processing of Metals
Journal of Materials Processing Technology | Year: 2016

Magnetic pulse cladding (MPC) technology, which is based on sequentially impact welding portions of long tubes, offers the distinct advantage of utilizing only a small amount of energy stored on the capacitor to fabricate bi-metal tubes. It remains necessary, however, to develop a method for successfully controlling and enhancing cladding quality during MPC. This paper provides insight into the plastic deformation behavior of bi-metal tubes subjected to progressive magnetic pulse force, using experiments with the FE method. The effect of the field shaper on the plastic deformation was also investigated to facilitate the field shaper design, where the parameters considered are the geometrical characteristics, known as the inclined angle α1 and α2 on the work zone of a field shaper. Results show that a bamboo-like shape produced on the outer surface of the clad tube was a result of inharmonious plastic deformation behavior. The modification of a field shaper by setting an inclined angle α2 works more effectively than shortening the feeding length in terms of improving bamboo-like shape, due to change in the magnetic field during the second step of the MPC process. Additionally, two kinds of typical plastic deformation responses corresponding to local and progressive collision patterns were identified during MPC. It was found that the inclined angle α2 and actively setting of inclined angle α1 at 3°on the work zone proved critical factors in determining plastic deformation response in the MPC process. These results demonstrate that the proposed numerical approach successfully elucidates fundamental details on critical behaviors during the MPC process, and can be used to assist process design. © 2015 Elsevier B.V. All rights reserved.


Wang C.,National Key Laboratory for Precision Hot Processing of Metals | Wang C.,Harbin Institute of Technology | Guo B.,National Key Laboratory for Precision Hot Processing of Metals | Guo B.,Harbin Institute of Technology | And 4 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2014

In the study of microforming meeting the needs of miniaturization of parts to be formed, the size effects are important parameters to be considered seriously. The objective of the investigation is to establish an explicit friction model in micro/mesoscale to calculate the coefficient of friction (COF) considering size effects, which is very helpful in analysis of microforming processes. With the open-closed pocket assumption, a scaling factor was adopted to describe the size effects on tribological behaviors in microforming. Based on the general Wanheim/Bay friction law, a relationship between the real contact area and the forming load was obtained considering the microscopical contact interface and the pressure induced by the trapped lubricant liquid. An explicit equation was developed including fraction of real contact area, scaling factor, and properties of lubricant. The effects of scaling factor and lubricant properties were discussed by analyzing its effects on the fraction of real contact area and coefficient of friction. With the developed model, the coefficient of friction was calculated and introduced into the finite element simulation of micro-upsetting deformation using ABAQUS software. When the scaling factor is less than 9, the size effect of friction becomes the main reason which affects the shape parameter in micro-upsetting deformation. Comparisons show that simulation results are in good agreement with that of experiments, which means that the developed model is suitable for analyzing size effects of friction in microforming. © 2014 Springer-Verlag London.

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