Study on anisotropic behavior of 7075 Al alloy after extrusion

Ni-Co-W alloy is expected to be a potential material for applications in national defense, military industry and petroleum exploration. Texture has a significant influence on alloy properties. In the present work, a 44Ni-37W-19Co alloy was prepared by vacuum melting and annealed at 1200 °C for 1h after forging, baring and hot stamping. The microstructure and texture at different positions were analyzed by optical micrographs (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and electron backscattering diffraction (EBSD) technique. The alloy presents equiaxial grains with an average size of ~90 μm and a nearly random texture. All the average pole intensity levels at surface, sub-surface and center are ~2. The anisotropy degree along the circumferential direction is less than that along the normal direction. The maximum and minimum differences of the radial pole intensity are 0.44 and 0.04, respectively. It is expected that this work will contribute to the controllable effects of microstructure and texture to improve the properties of hot-stamped high-density Ni-Co-W alloys.

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Microstructure and texture of a novel hot-stamped high-density Ni-Co-W alloy

Xie

Zhao

et al. 2022

“…As lightweight structural materials, 7075 aluminium alloys have high strength and hardness and are widely used in aviation, aerospace and military applications. With the ongoing expansion of industrial demands, higher requirements are placed on the strength, hardness and plastic deformation capacity of traditional 7075 aluminium alloys [1]. Equal-channel angular pressing (ECAP) is one of the most effective severe plastic deformation methods for the preparation of bulk fine-grained materials.…”

Section: Introductionmentioning

confidence: 99%

Effect of rapid cooling on the microstructure and properties of fine-grained 7075 aluminium alloy under friction stir welding

Luo

Yang

Quan

et al. 2022

In this study, 7075 aluminium alloy plates with a fine-grained structure were produced by four-pass equal-channel angular pressing and subsequently joined at room temperature (297 K) using carbon dioxide (CO2)-assisted cooling friction stir welding. Electron backscatter diffraction, X-ray diffraction, Thermocouple measuring instrument,optical microscopy and microhardness testing were used to investigate the microstructural and mechanical characteristics of friction stir welded joints. The results indicated that the maximum temperatures of welded joints at room temperature and CO2 - assisted were 673 K and 568 K, macroscopic surfaces of the welded joints under CO2-assisted cooling were smoother than those created under room temperature; this was because the rapid cooling of liquid CO2 inhibited the growth of grains and, following dynamic recrystallisation, the grain size was finer (~2.9 μm). Compared with the fine-grained base material (BM), the proportion of large-angle grain boundaries in the stir zone region of the welded joints increased under both conditions, and the anisotropy was weakened. The precipitation hardening of the joints was obvious; the welded joints appeared to soften at room temperature, while the hardness of the joints was the same as that of the fine-grained BM under the CO2-assisted cooling condition.

“…During the design of a new airframe, the emphasis is always put on mechanical life for which a period of approximately 20 years is planned. Nevertheless, beyond those 20 years of service, the aircraft is qualified of aging as their mechanical problems (such as fatigue) become somehow less important than the problems related to corrosion of aluminum structural parts [1,2]. This is especially the case when aircraft operational environments are chemically aggressive, e.g., industrially polluted and seacoast atmospheres [3,4].…”

Section: Introductionmentioning

confidence: 99%

Characterization and evaluation of stable localized corrosion in a 7075-T6 aluminum alloy FSW joint before and after anodizing treatment

Yang

Zou

et al. 2022

The microstructure and corrosion processes of a friction stir welded (FSW) 7075-T6 aluminum alloy joint, before and after anodizing surface treatment, have been characterized by advanced techniques, and the feasibility of anodizing treatment as a corrosion mitigation method has been evaluated. The results showed that different zones of the FSW joint had distinctly different microstructure and consequently different corrosion behavior in NaCl solution. Stable localized corrosion occurred in the transitional regions between the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ), and was characterized by intergranular corrosion. The intergranular corrosion was ascribed to the galvanic coupling effect between Cu-rich grain boundary precipitates and the precipitates free zones (PFZs). Although anodizing and the subsequent sealing treatments could greatly improve the corrosion resistance of the base metal, the TMAZ / HAZ transition regions still showed much higher corrosion susceptibility than other regions. The high corrosion susceptibility of the FSW joint after anodizing treatment is not ascribed to the difference of the anodic oxide film in the regions, but the heterogeneous microstructure of the alloy beneath the anodic film. The present paper has shown that the stable localized corrosion in the FSW joint is intrinsically stemmed from the welding process itself and traditional mitigation method such as anodizing treatment cannot solve the problem; more effective corrosion mitigation methods are still awaited.