Papers by Keyword: 7050 Aluminium Alloy

Abstract: In order to study the quenching residual stress of typical aluminum alloy component used in aerospace, the finite element (FE) model of quenching process of 7050 aluminum alloy cross-shaped component was established based on heat transfer theory and elastic-plastic mechanics theory, the distribution regularities of quenching residual stress field of cross-shaped component was analyzed. The results indicate that the residual stress distribution of web of cross-shaped component is similar to the residual stress distribution of thick plate, the large tensile stress concentration is exist in web plate and the connection part of the stiffener with a certain influence area. The error data of the component contour deformation were processed and the component deformation contour was fitted, which makes the test result of the contour method and FE simulation result have good consistency. The results of the study provides guidance for quenching residual stress reduction of aviation aluminum alloy components and provides the basis for calculating of machining deformation of monolithic component.

Abstract: The age-hardening precipitation of double peak during two-stage aging process in 7050 aluminum alloy is studied in this paper. The results show that the first peak is strengthened by high-density GP zones, whereas the second aging peak is mainly strengthened by h¢ phases with a certain size, which suggests that the strengthening effect of both h¢ phases and GP zones are better than that of individual GP zones.

Abstract: The solution treatment and solution and aging treatment (T6) were disposed on 7050 aluminium alloy, then local processed by laser shock processing (LSP) with high-rate neodymium glass laser. The microhardness and residual stress on the surface of 7050 aluminium alloy were tested, then how the microstructure influences the residual stress on the surface of 7050 aluminium alloy by laser shock processing was analysed. The results show that the microhardness and residual compressive stress on the surface of 7050 aluminium alloy treated by solution and aging treatment was higher, and decreased obviously treated by solution treatment; the microhardness and residual compressive stress on the surface of 7050 aluminium alloy increased obviously by solution treatment and solution and aging treatment after laser shock processing; treated by solution treatment and solution and aging treatment, the microhardness and residual compressive stress of the material with uniform original structure was higher than the material with nonuniform original structure.

Abstract: Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy 162mm ingots and study its effect on the as-cast microstructure. Effects of electromagnetic field parameters such as frequency and current intensity on microstructures were systemically investigated. The results showed that LFEC has a significant grain refining effect on 7050 alloy. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed or nearly equiaxed grains which are much finer and more uniform than those of DC cast ingot. It was also found that electromagnetic field frequency and current intensity play important roles on the microstructure refinement. The discussion was mainly focused on the mechanism of grain refinement by LFEC process.

Abstract: Grain refinement is quite important for producing 7050 alloy ingot especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ310 ingots and study the effect of electromagnetic field and grain refiner on the microstructure of 7050 alloy ingots. The results showed that both grain refiner and low frequency electromagnetic field can result in some grain refinement of 7050 alloy. However, the low frequency electromagnetic field shows more remarkable grain refinement. For the grain refined alloy by grain refiner, further significant grain refinement can be achieved with the application of low frequency electromagnetic field. The finest microstructure was achieved by combining the applications of both grain refiner and electromagnetic field.

Abstract: Imposing ultrasound on D.C.casting of the 7050 aluminum alloy could refine grains significantly. Among the physical effects accompanying the propagation of high power ultrasonic oscillations in melt, cavitation, or the formation of cavities filled mainly with gases dissolved in the molten melt. In this research, we have analyzed solidified structures which influenced by different power of ultrasound via using cavitation theory and experiment. The results indicated that after treating by ultrasound, the solidified structures of the aluminum alloy could be refined considerably and the degree of the structure refining rose along with the increase of the ultrasound power. Software MATLAB was chosen to simulate the relationship between acoustic pressure and relative radii of cavitation bubbles, ultrasonic frequency and relative radii and initial equilibrium radii and relative radii respectively. After that, the mechanism of grain refining have been discussed under the condition of stable cavitation and transient cavitation, providing some related references for ultrasound applying in the field of foundry industry.

Abstract: The error distribution of residual stress tested by X-ray diffraction on 7050 aluminum alloy was studied. In this paper, residual stress was measured, independently and repeatedly, many times on 7050 aluminum alloy with X-ray diffraction, then the errors about 50 stress values within the range of 30MPa were analyzed by the hypothesis testing. The results indicate that the errors of the residual stress measurement on 7050 aluminum alloy were followed the law of normal distribution about and the errors can be estimated by the least square calculator. The research lays the foundation to subsequent researches on the inherent law of the residual stress measurement with X-ray diffraction and the residual stress distribution and accuracy of stress of material surface.

Abstract: Stress corrosion cracking of 7050 aluminum alloys and ASTM A470 steel in the turbo expander and steam/gas turbine industry can cause expensive catastrophic failures, especially for turbo machinery systems performing in hostile, corrosive environments. Commercially available inhibitors were investigated for their effectiveness in reducing and controlling the corrosion susceptibility. Inhibitor effectiveness was confirmed with electrochemical corrosion techniques in different solutions. Polarization resistance increased with concentration of corrosion inhibitor due to film formation and displacement of water molecules. Cyclic polarization behavior for samples in the 1.0% and 5.0% inhibitors showed a shift in the passive film breakdown potential. The substantial increase in the passive range has positive consequences for neutralizing pitting and crevice corrosion cell chemistry. The strain to failure and tensile strength obtained from the slow strain rate studies for both alloys showed pronounced improvement due to corrosion inhibitor ability to mitigate SCC; the fractographic analysis showed a changed morphology with ductile overload as the primary failure mode instead of transgranular or intergranular cracking.

Abstract: The distribution of mechanical property in the weld zone of friction stir welded 7050 aluminum alloy joint along the plane perpendicular to the welding direction was experimentally investigated by the non-contact measurement method. The results show that the elastic modulus presents a W-shape distribution across the weld zone. The elastic modulus in the weld nugget zone is increased due to the grain refinement. In addition, the elastic modulus in the advancing side is slightly less than that in the retreating side possibly because of the relatively higher temperature in the advancing side during the welding process. The strength in the vicinity of weld center is decreased while the ductility is enhanced. The tensile strength and yield strength in the weld nugget zone and thermo-mechanically affected zone are significantly decreased while the elongation is increased due to the change of strengthening mechanism. In the heat affected zone the strength is decreased compared to the base material because the second phase grows up.

Abstract: Constrained groove pressing is a simple and effective method of grain refinement. Using the experimental data obtained by regression analysis, this paper analyzes the simulation of the four pass constrained groove pressing deformation of 7050 aluminum alloy. The simulation results show that the grain size of the billet is refined significantly after four pass constrained groove pressing deformation and decreases from the original 90 μm to a minimum of 14.0 μm. With the increase of the number of deformation passes, refinement effect becomes weakened gradually, the grain size tends to stabilize and the organization is more uniform.