Functional and Functionally Structured Materials II

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Authors: Xin Tong Lian, Wen Ru Sun, Xin Xin, Dan Dan Zheng, Shou Ren Guo
Abstract: Microstructure and mechanical properties of Ni-Cr alloys with various contents of Phosphorus (P) have been investigated. It is found that the increase of phosphorus refined dendritic structures in as-cast alloys and decreased micro-segregation of Chromium (Cr) element. α-Cr which precipitated during hot-rolling process was obviously inhibited by phosphorus because of its prior occupancy on grain boundaries and decreasing precipitation driving force of α-Cr. Tensile and impact properties were examined on samples under different heat treatments. Though the yield strength of as-rolled alloys was increased by precipitation of α-Cr, the elongation and impact energies were reduced. It is worthy to note that impact energies of samples solutioned at 950°C increased with the increasing phosphorus. The results indicated that dislocations are markedly effected by phosphorus which is probably the reason for improving impact energies.
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Authors: Sha Zhang, An Wen Zhang, Wei Yang Wang, Xin Xin, Kai Zhang
Abstract: The segregation and precipitation behavior of phosphoruswas studied in aNi-Fe-Cr base wroughtsuperalloy. The precipitation behavior of phosphides in the alloy contained 0.025% Pwas examined after soaking at 750-1080°C to determine the precipitation temperature range of MNP-type phosphide. The microstructuresunder these various conditions wereinvestigated by scanning electron microscope(SEM) and energy dispersive spectroscopy (EDS). The precipitation temperature of the phosphide in the alloy was determined to be in the range of 850-1040 °C and the precipitation peak temperature was around 980°C.In addition, the melting temperatureof the phosphide was determined to be between 1200 °C and 1250 °C. The current results indicate the tendency of phosphorus segregated at grain boundaries.
150
Authors: Xiao Hong Wang, Zheng Wei Peng, Gao Xu Li, Yuan Hua Lin, Hai Lun Wang
Abstract: Aiming at the special service environment of aluminum alloy drill pipe, in this paper, the influence of extrusion texture on the mechanical and electrochemical properties of aluminum alloy drill pipe was studied. And the macroscopic textures of longitudinal profile and cross section of aluminum alloy drill pipe were tested, and the tensile, compressive and impact mechanical properties were tested, followed by immersion and electrochemical testing. The results show that the texture which 2A12T4 aluminum alloy drill pipe contains is <001> and <111> along the extrusion direction and <223>, <101> in the transverse direction. The test results of mechanical properties show that the extruded texture will affects the mechanical properties of material. When the cross section and longitudinal profile samples of 2A12T4 were soaked in 3.5% NaCl solution at 25°C, 60°C and 90°C, their corrosion resistance are different. The pits of transverse specimens exhibit a dispersed distribution and that of longitudinal specimens are distributed along the extrusion direction.
157
Authors: Xian Ye Liang, Guang Bao Mi, Liang Ju He, Pei Jie Li
Abstract: The abnormal local friction and wear phenomena usually generate during the service of the titanium alloy rotor /stator parts of the aero engine compressor under high temperature conditions. This phenomenon is the main cause of the occurrence of titanium fire failure and has great harm. In the present investigation the friction and wear behavior of the combustion resistant titanium alloy at high temperature was studied by finite element numerical simulation and experimental verification of the pin-on-disk model. Firstly, the geometrical model of the round bottom pin-on-disk contact was established. Then, the friction process was simulated by the Coulomb friction model. The ALE technique of ABAQUS was applied to move the contact nodes and update the grid. The finite element simulation of the ARCHARD wear model was realized. In order to deal with the increasing contact area, a simplify wear direction was proposed. Finally, the wear depth and volume was calculated and the wear law at 500 °C -900 °C was revealed. The results show that the wear process is gentle at the temperature of 500-700 °C, and the wear depth is within 0.08mm when the sliding distance reaches 1800m. When the temperature exceeds 800 °C, the wear rate increased sharply and the wear depth beyond 0.1mm, the FE result is consistent with the test results.
168
Authors: Hong Jun Hu, Zhao Sun, Ding Fei Zhang
Abstract: Based on characteristics of direct extrusion for magnesium alloy seamless tube and continuous equal channel angular pressing (ECAP) of tubes, a new composite extrusion process of tubes including direct extrusion and many steps ECAP was invented firstly, which are shorten for TES process in this paper. A three-dimensional finite element thermo-mechanical coupled model and conditions for TES process were established. The extrusion process and cumulative strains evolution during TES process were simulated. The results show that TES process can improve the cumulative strains significantly. The microstructures observations of longitudinal sections for tubes fabricated by direct extrusion and TES process were carried out. It was found that when the extrusion temperature was 400°C, and extrusion ratio was 8.4 and the channel angle was 150°, TES process can refine the microstructures of tubes effectively.
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Authors: Yang Wu, Hua Mao, Qing Bo Yang, Zhi Qing Zhang
Abstract: In this work, the ratio of rotation rate to advancing speed was fixed to 10 to fabricate friction stir welding (FSW) butt joints of 2195 - T8 plates with 7.5 mm in thickness. The results revealed that the heat input of joints along the vertical direction varied with the welding parameters though these parameters had a same ratio. 500-50 and 600-60 joints failed in the thermal affected zone and thermal mechanical affected zone (TAZ/TMAZ), while other joints all failed in stirred zone (SZ). The hardness profile across the joints showed a similar W shape, while the hardness in bottom area increased with the increasing of parameters. Lazy S and kissing - bond defects appeared in all of these joints, and over - burn defect was also found in 1000-100 joint. It is concluded that the heat input distribution gradient during FSW across the joints becomes non-uniform and a sudden change between upper and lower areas even occurs.
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Authors: Yong Gang Hao, Peng Lin, Bao You Zhang, Xiao Lei Cui, Chang Jiang Zhang, Cheng Zhong Chi
Abstract: The planar anisotropy (PA) and tension-compression asymmetry (TCA) of the commercially pure titanium (CP-Ti) were investigated through uniaxial tension and compression experiments at room temperature. By deep drawing experiment, the formability and the earing profile for the CP-Ti were studied at room temperature. The deep drawing simulations using the hardening rules of uniaxial tensile or compression curves were compared with experimental results. The results show that the CP-Ti has obvious PA, and the plastic strain ratios r0, r45 and r90 are 1.47, 1.64 and 2.05, respectively. The CP-Ti sheet shows the tension-compression asymmetry of yielding and hardening. The TCA also shows obvious PA. The tension-compression yield strength ratio of 0°, 45° and 90° to the rolling direction are 1.12, 1.08, 1.04, and the tension-compression hardening exponent ratio are 0.86, 0.8 and 0.62, respectively. The simulative results without considering TCA indicate that the forming force, the wall thickness and earing profile are not in good agreement with the experimental ones. Therefore, the earing appeared in 45° is contribution of the PA and TCA. The TCA will reduce the thickness of the deep drawing parts, increase the earing ratio and affect the drawing force.
190
Authors: Zhi Jun Xu, Yin Li Chen, Lan Su, He Wei, Ze Sheng Liu
Abstract: The relationship between textures and properties of Cu-Ni-Si alloys was analyzed in this paper. The texture evolution of high strength and high elasticity Cu-Ni-Si alloy in different cold rolling and heat treatment processes was researched by the fiber analysis. And the electrical conductivity and tensile strength in different directions of the Cu-Ni-Si alloy were measured. The results showed that there were mainly Brass texture B{011}<211>,Gauss texture G {011}<100> and Copper texture C {211}<111> in the cold-rolled Cu-Ni-Si alloy. With the increase of cold deformation, the Copper texture was weakening, while the Gauss texture and Brass texture increased. When the deformation was 65%, there was almost no Copper texture in the alloy, and only Gauss and Brass texture exist. After the solid solution and aging process, both the Gauss and Brass texture were weakening, while the S texture {123}<624> increased greatly. After 4 hours aging the conductivity was up to 42.7% IACS. And the tensile strength of different directions is 745.5MPa (0°direction,RD), 684.5MPa (90°direction,TD) and 653.5MPa (45°direction) respectively. Based on the above results, maximum Schmid factor of different textures in different directions and the Index of Plane Anisotropy (IPA) were been analyzed.
196
Authors: Dong Mei Liu, Qiang Song Wang, Wei Yuan, Xu Jun Mi
Abstract: A comparative study on the friction and wear properties of three kinds of copper alloys, including Cu-Ni based, Cu-Al and Cu-Be alloys was carried out in this study. The friction pair was stainless steel, and both dry and MoS2 lubrication friction experiments were investigated. During the experiments, different loads were chosen for different alloys. It was found that under dry friction condition, the friction coefficients of both Cu-Ni based and Cu-Al alloys did not change as the loads changes, whereas the friction coefficient of Cu-Be alloy increased as the loads increases. Under lubrication friction condition, the friction coefficients of all three alloys did not change as the load changes. The results show that the dry friction coefficient of Cu-Ni based alloy was the largest (0.74), the Cu-Al alloy next (0.60), and the Cu-Be alloy had the smallest dry friction coefficient (0.54). The lubrication friction coefficient of Cu-Ni based and Cu-Be was equal and relatively smaller (0.12), whereas the Cu-Al alloy had a relative larger lubrication friction coefficient (0.27). The microstructure observations were consistent with the friction and wear performance, and the SEM results show that different wear mechanisms were dominated for different alloys.
205
Authors: Bing Wu, Ao Lei Jiang, Hao Lu, Hong Liang Zheng, Xue Lei Tian
Abstract: A mathematical physical model of microstructure evolution in Al-Si eutectic solidification process based on cellular automaton (CA) model was developed. Before the establishment of the model, the relevant near-eutectic experiments were carried out to analyze the effect of cooling rates measured by temperature curves on the eutectic structure which was observed through optical microscope (OM) and scanning electron microscope (SEM). Then a multiphase nucleation-growth CA model was applied to simulate the Al-Si irregular eutectic structure. The model adopted an alternative nucleation mechanism to investigate the influence of the critical nucleation value associated with solute concentration during solidification process. The growth kinetics took into account the solute and thermal field. According to the crystal structure of nonfaceted eutectic Al and faceted eutectic Si, different capturing rules were employed to calculate the growth of eutectic. In addition, the model was also used to research the irregular eutectic growth under different undercooling conditions. The results revealed that smaller critical nucleation value (absolute value) or higher eutectic undercooling tended to get a more refined eutectic microstructure. By compared with experimental results, it is indicated that the microstructure evolution of Al-Si eutectic growth can be reproduced quantitatively by numerical simulation with this model.
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