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Tao J.-Q.,No59 Institute Of China Ordnance Industry | Cheng Y.-S.,Harbin Institute of Technology | Huang S.-D.,No59 Institute Of China Ordnance Industry | Peng F.-F.,No59 Institute Of China Ordnance Industry | And 4 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

In order to improve the mechanical properties of ZK60 magnesium alloy components, the multi-axial forging (MAF) plus partial remelting route was used in this study. The effect of remelting temperature and holding time on microstructure of semi-solid ZK60 magnesium alloy was also studied. Furthermore, the tensile mechanical properties of ZK60 magnesium alloy components produced by multi-axial forging plus partial remelting route were compared at different thixoforging temperatures. The results showed that the multi-axial forging followed by partial remelting is an effective route to produce semi-solid ZK60 magnesium alloy for thixoforming. During the partial remelting, with prolonging the holding time and increasing the remelting temperatures, the solid grain size increased. With the increase of remelting temperature, the degree of spheroidization tended to be improved. With increasing the thixoforming temperature from 560°C to 574°C, the tensile mechanical properties of ZK60 magnesium alloy were improved. © 2012 The Nonferrous Metals Society of China.

Li Z.-S.,Chongqing University | Li Z.-S.,No59 Institute Of China Ordnance Industry | Wu H.-L.,No59 Institute Of China Ordnance Industry | Pan F.-S.,Chongqing University | And 2 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2011

Hot plastic deformation behavior of novel Al-Zn-Mg-Cu alloy was studied by isothermal compression at 300-450°C and strain rate of 10-3 - 1 s-1. The processing map was developed on the basis of dynamic material model (DMM). The results show that the alloy exhibits steady-state flow characteristics and belongs to positive strain rate sensitized material during hot compression deformation. The efficiency of power dissipation is much higher at high temperature of 450°C and low strain rate of 0.001 s-1, and the maximum is about 0.61. The optimum processing parameters obtained by the map in this experiment are in the temperature range of 390-410°C and the strain rate range of 0.018~0.135 s-1.

Yang R.-J.,Nanjing University of Science and Technology | Wang L.-M.,Nanjing University of Science and Technology | Xiu G.,Nanjing University of Science and Technology | Li K.,No59 Institute Of China Ordnance Industry
Dandao Xuebao/Journal of Ballistics | Year: 2011

To effectively use radar measured data to reconstruct actual trajectory, the nonlinear filtering model of trajectory was established considering random wind; the integral predictive Unscented Kalman Filter (UKF) algorithm was developed as a tool for trajectory reconstruction. When the UKF was applied to reconstruct trajectory online, the uncertain initial conditions induced large initial estimated errors of ballistic parameters. A novel and efficient smoother Unscented Rauch-Tung-Striebel Smoother (URTSS) was introduced to solve this problem. By URTSS, the final value of the state and covariance were transmitted back to the initial time, and the optimal estimated trajectory was obtained. Simulation result shows that it is effective to apply UKF method to reconstruct trajectory, and URTSS can reduce estimated errors of ballistic parameters, especially the estimated errors of the projectile muzzle velocity and the wind. The precision of reconstruction of actual trajectory using radar measured data is improved.

Zhao G.-Z.,No59 Institute Of China Ordnance Industry | Yang L.,China Coal Research Institute | Duan X.-X.,China Coal Research Institute | Ren X.-H.,China Coal Research Institute | And 4 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Microstructure evolution and mechanical properties of AZ80 alloy reheated from the as-cast and deformed states were investigated. A new method, cyclic closed-die forging (CCDF), was employed to deformation of AZ80 as a recrystallization and partial melting (RAP) process. During partial remelting, finer, rounder and more homogeneous grains can be obtained from CCDF-formed alloys than from as-cast alloys. Prolonging isothermal holding time from 0 to 40 min, the mean grain size of solid particles in as-cast state decreased initially and then increased, however, that of CCDF-formed alloys increased continuously. The degree of spheroidization was improved in as-cast alloys with prolonging holding time. In contrast, in CCDF-formed alloys, the value of shape factor increased initially and then decreased. Microstructure evolution during remelting is dominated by many factors, for example distortion energy providing recrystallization driving force, Ostwald ripening mechanism, grain coalescence. Compared with the as-cast alloys, the CCDF-formed AZ80 alloy got a significant improvement in tensile properties. YS, UTS and elongation increased by 89%, 45% and 242% respectively. This can be mainly attributed to the grain refinement and elimination of defects. © 2012 The Nonferrous Metals Society of China.

Jiang Z.T.,Chongqing University | Jiang Z.T.,Chongqing University of Arts and Sciences | Jiang B.,Chongqing University | Jiang B.,Chongqing Academy of Science and Technology | And 4 more authors.
Materials Science Forum | Year: 2015

In the present work, the microstructure evolution of Mg-4Al-2.5Ca alloy during solidification was investigated by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and differential scanning calorimetry (DSC). The results showed that the as-cast microstructure was typical dendritic structure, consisting of α-Mg and the Al2Ca with a C15 structure formed at inter-dendritic regions. But during slow solidification, the sequence of phase formation of this alloy consisted of following stages: L→ L + α-Mg → L + α-Mg + (Mg, Al)2Ca → α-Mg + (Mg, Al)2Ca + Al2Ca → α-Mg + Al2Ca. Thermal analysis showed that the (Mg, Al)2Ca and Al2Ca phase separation temperature was about 520℃ and 510℃ respectively, which is different from thermodynamic calculation. With the temperature decreasing, the liquid (Mg, Al)2Ca phase with thick and continuous morphology transformed into lamellar-shaped eutectic phase, and parts of (Mg, Al)2Ca phase translated into Al2Ca phase with bone-shaped and needle-like. © (2015) Trans Tech Publications, Switzerland.

He J.,Chongqing University | Jiang B.,Chongqing University | Jiang B.,Chongqing Academy of Science and Technology | Jiang B.,National Center for Quality Supervision and Inspection of Magnesium and Magnesium Alloy Products | And 6 more authors.
Journal of Alloys and Compounds | Year: 2015

The mechanical responses of AZ31 Mg alloy sheet processed by pre-hardened at different directions tilting 45° and 90° to the extrusion direction (ED) were compared and evaluated in correlation with the concurrent microstructure and texture evolution. The amount of deformation twinning was sensitive to crystal orientation with respect to the direction of pre-hardening. The tensile twinning could promote the nucleation rate in the following static recrystallization. In addition, the reorientation of the c-axis caused by the {10 -12} twins had a great influence on work hardening. Twinning could effectively coordinate the deformation texture, and the basal texture intensity was reduced to half after pre-hardening 7% along the transverse direction (TD) after annealing. © 2014 Elsevier B.V. All rights reserved.

Luo J.,Chongqing University | Zhao G.-J.,Chongqing University | Wang X.-J.,Chongqing University | Wu W.,No59 Institute Of China Ordnance Industry | Xu X.-L.,No59 Institute Of China Ordnance Industry
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2010

CT-25 special friction welding machine is used to weld 35CrMnSi/T3 with different inertial flywheel rotation speeds. The interface microcosmic binding characteristics and microstructure changes are observed by SEM. The element diffusion near the interface is detected by EDS and the microhardness of plastic deformation zone in Cu matrix is tested. The results show that, when the inertial flywheel rotation speed increases, friction heat of primary pressure increases significantly, more plastic deformation forms between the contact surfaces by secondary pressure, and bonding of work pieces is promoted. When the flywheel rotation speed is 3000 r/min, the joint of 35CrMnSi/T3 by inertial radial friction welding process gets clean binding domain, elements obviously diffuses, the fine-grain α-Fe and ε-Cu structure forms in recrystallization zone and the welding effect is good. The microhardness of interface region in Cu matrix is increased by violent plastic deformation.

Luo J.,Chongqing University | Sun Y.,Chongqing University | Liu D.-J.,Chongqing University | Wu W.,No59 Institute Of China Ordnance Industry | Xu X.-L.,No59 Institute Of China Ordnance Industry
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2010

Based on the difficulty of inertia radial friction welding small size T3/35CrMnSi dissimilar metal materials, the characteristics of joints of T3/35CrMnSi were analyzed by SEM, EDS, microhardness test and shear strength test. The results show that plastic deformation layer, dynamic recrystallization, and diffusion and dissolution of elements occur in the joint transition region, achieving metallurgical bonding. The thickness of the plastic deformation layer changes with spindle speed, friction pressure, forging pressure; when the thickness is about 5 μm, the interface quality is the best. The joint mechanical properties and the width of heat affected zone are relative to the plastic deformation layer, martensitic transformation and material properties. In the case that the spindle speed is more than 1800 r/min, the forging pressure is more than 190 MPa, the welding joints are bonded successfully and have no local spot defects.

Wang C.,No59 Institute Of China Ordnance Industry | Mei H.,No59 Institute Of China Ordnance Industry | Li R.,No59 Institute Of China Ordnance Industry | Li D.,No59 Institute Of China Ordnance Industry | And 6 more authors.
Acta Metallurgica Sinica (English Letters) | Year: 2013

The effects of CEC passes, isothermal holding time and reheating temperature on the microstructure evolution and grain coarsening behaviour of AZ61 magnesium alloy produced by the recrystallisation and partialmelting (RAP) process were investigated. Before partial remelting, as-cast AZ61 alloy was deformed by cyclic extrusion compression (CEC) with one pass and two pass at 330 °C. After CEC, the microstructure consisted of unrecrystallized grains and deformed eutectic compounds. Increasing isothermal holding time resulted in the formation of spheroidal grains surrounded by liquid films. With increasing the isothermal holding time, the solid grain size increased and the degree of spheroidization was improved. With increasing the reheating temperature, namely increasing liquid fraction, the solid grain size obviously decreased during the period from 560 °C to 570 °C and then slightly increased after 570 °C, while the shape factor increased monotonously. During partial remelting, increasing reheating temperature can properly short the isothermal holding time to obtain fine structure. Moreover, increasing the numbers of CEC passes could produce finer semi-solid microstructure. The coarsening behavior of solid grains in the semi-solid state obeys Ostwald ripening and grain coalescence mechanisms. The coarsening rate constant, K, was 80 μm3 s-1 for samples partially remelted at 595 °C. After CEC plus partial remelting, the ideal and fine semi-solid state structure can be obtained, which was suitable for thixoforming. © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.

Chen D.,No59 Institute Of China Ordnance Industry | Wu H.,No59 Institute Of China Ordnance Industry | Li Z.,No59 Institute Of China Ordnance Industry | Zhang L.,No59 Institute Of China Ordnance Industry | Fu Y.,No59 Institute Of China Ordnance Industry
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2016

Molybdenum alloys doped with different mass fraction of La2O3/Y2O3 have been produced by powder metallurgical processing in this paper. The results were concluded based on the analysis of the alloys phase compositiong, microstructure, fracture surface photograph and mechanical property. Results show that the main crystal phases are La2O3, Y2O3 and Mo. The grain size of the forged molybdenum alloy decrease as the mass fraction of La2O3/Y2O3 increasing. And the longitudinal section microstructure of the forged molybdenum is fibrous deformation texture. It is proved that the forged Mo(La2O3)3.0 (Y2O3)0.5 alloy fracture surface of cross section characterize with dimple fracture and a small mount of cleavage fracture, longitudinal section shows evident characteristic of intergranular brittle rupture. The flexural strength curve and flexural angles curve of the alloy exhibits a mountain shape when the content of La2O3/Y2O3 increases, the peak flexural strength and flexural angles of Mo(La2O3)3.0 (Y2O3)0.5 alloy in the experiment is 1133 MPa and 38°. © 2016, Beijing Research Institute of Powder Metallurgy. All right reserved.

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