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Enhancement of strength mechanical and corrosion resistance of 7055 alloy with minor Sc and Y addition
No full textA new type of 7055-Y-Sc alloy with high strength and corrosion resistance was prepared. Eutectic Al _3 Y particles with sizes in the range of 500–600 nm were found in the as-cast structure of the 7055-Y-Sc alloys. The addition of Y significantly accelerated the precipitation of Al _3 Zr with L1 _2 structure in Al–Zr–Y alloy, and the number density of Al _3 (Zr, Y) precipitates was almost a grade higher than that of Al _3 Zr. In the process of aging at 120 ℃/12 h, the nano scale L1 _2 -type Al _3 (Sc _x Y _y ) phase nucleated uniformly within the Al matrix and nonuniformly on the dislocation. The grain size decreased from 100–200 um in 7055-Y-0Sc to 40–50 um in 7055-Y-0.25Sc, the percentage of Sc continued to increase, and the grain size remained unchanged or even increased, thereby decreasing the Vickers hardness of 7055-Y-Sc alloys from 196.4 HV to 187.9 HV. After aging, the hardness and tensile properties of 7055-Y-Sc alloy showed good performance. The effective Sc proportion of the 7055-Y-Sc alloy was 0.25%. Its tensile strength was 398.6 MPa. Its conductivity was 33.8% IACS. The current corrosion density was 6.7 × 10 ^−8 A cm ^−2 , its good strength, corrosion resistance and conductivity make the studied alloy to be a promising material
Superplasticity in a 7055 aluminum alloy processed by ECAE and subsequent isothermal rolling
No full textyesSuperplasticity in a 7055 aluminum alloy processed by ECAE and subsequent isothermal rolling The superplastic properties and microstructural evolution of a 7055 aluminum alloy was examined in tension at temperatures ranging from 300 to 450°C and strain rates ranging from 2.7×10⁻⁵ to 5.6×10⁻² s⁻¹Belgorod State Universit
Microstructure Evolution and Recrystallization Resistance of a 7055 Alloy Fabricated by Spray Forming Technology and by Conventional Ingot Metallurgy
Get PDFThe effect of different fabricating processes (spray forming and conventional casting) and homogenization treatment on the microstructure of an 7055 alloy was investigated by optical microscopy (OM), scanning electron microscopy (SEM), electron probe X-ray micro-analyzer (EPMA), and transmission electron microscopy (TEM). It was found that the grain size of the as-deposited (spray formed) 7055 alloy had half the size as that of the as-cast 7055 alloy and there was no Al2CuMg phase that embedded in the coarse Mg(Zn, Cu, Al)2 phase distributed along the grain boundaries in the as-deposited 7055 alloy. No segregation of zirconium was observed in the as-deposited 7055 alloy. After homogenization heating at 350 °C/5 hours + 470 °C/24 hours, Al3Zr dispersoids were inhomogeneously distributed within grains in the traditionally cast 7055 alloy, while more homogeneously distributed within grains in the spray-formed 7055 alloy. Compared with the traditional cast 7055 alloy, the uniform distribution of Al3Zr dispersoids in the spray-formed 7055 alloy retards recrystallization more effectively. This investigation highlights the advantage of spray forming technology on improving microstructure of a 7055 alloy.acceptedVersionThis is a post-peer-review, pre-copyedit version of an article. Locked until 4.8.2021 due to copyright restrictions. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11661-020-05931-
Comparison of high-strength aluminum alloy 7055-T7751 and standard alloy 7075-T651
No full textIt has been reported by Alcoa that alloy 7055-T7751 is 25% stronger than alloy 7075-T6 and that corrosion resistance of alloy 7055-T7751 is between that of alloys 7150-T6 and 7150-T77. Mechanical properties and corrosion resistance of these alloys were compared in side by side testing. The results for two commercial lots of these alloys demonstrate that alloy 7055-T7751 is approximately 5% stronger than 7075-T651, but is 5-7% below strengths reported by Alcoa. Resistance to stress-corrosion cracking and corrosion-fatigue in air and artificial seawater were equivalent, but in 3.5% NaCl solution 7055-T7751 was more susceptible to corrosion-fatigue at low stress intensities under conditions tested.Includes bibliographical references (leaves 41-42)California State University, Northridge. Department of Engineering
The improvement of constituent dissolution and mechanical properties of 7055 aluminum alloy by stepped heat treatments
No full textThe effects of stepped heat treatments on the dissolution of soluble remnant constituents and the mechanical properties of a 7055 aluminum alloy were investigated. Optical and electron microscopy observations and electron probe microanalysis were used to analyze the microstructures and tensile fracture surfaces of 7055 alloy processed via various treatment schedules. The observations revealed that by using a lower temperature pretreatment, the individual constituent phases in multi-phase eutectics grew into separated constituent particles and the η phase dissolved completely. Consequently the initial melting temperature of 7055 alloy ingots was increased. It was shown that a suitable pretreatment could enable subsequent high temperature solution treatment and complete dissolution of the constituent particles in 7055 alloys without overheating. This in turn increased the tensile strength and fracture toughness of the 7055 alloy to 805 MPa and 41.5 MPam 1/2, respectively, with approximately 9% tensile elongation. The improvements were attributed to a combination of reduced fracture initiation by fracture of constituent particles near crack tips and an improved age hardening response resulting from the increased concentration of elements dissolved in the matrix. © 2003 Elsevier B.V. All rights reserved
Effect of T6 and Re-Aging Heat Treatment on Mechanical Properties of 7055 Aluminum Alloy
No full textHeat treatable aluminum alloys such as 7075 and
7055, because of high strength and low density, are used widely in
aircraft industry. For best mechanical properties, T6 heat treatment
has recommended for this regards, but this temper treatment is
sensitive to corrosion induced and Stress Corrosion Cracking (SCC)
damage. For improving this property, the over-aging treatment (T7)
applies to this alloy, but it decreases the mechanical properties up to
30 percent. Hence, to increase the mechanical properties, without any
remarkable decrease in SCC resistant, Retrogression and Re-Aging
(RRA) heat treatment is used. This treatment performs in a relatively
short time. In this paper, the RRA heat treatment was applied to 7055
aluminum alloy and then effect of RRA time on the mechanical
properties of 7055 has been investigated. The results show that the
40-minute time is suitable time for retrogression of 7055 aluminum
alloy and ultimate strength increases up to 625MPa
Influence of carbon sources on the production and characterization of the exopolysaccharide (EPS) by Bacillus sphaericus 7055 Strain
Get PDFIn this study, EPS produced by five Bacillus spp. strains was determined. The only one strain (B. sphaericus 7055) was selected due to its high EPS production and it was investigated by growing this strain in LB broth medium containing various carbon sources. The highest EPS production of this strain was found in medium containing fructose. However, the effect of different concentrations of fructose and molasses on EPS production by the strain was studied. The maximum EPS yield of the strain 7055 was recorded with 2.5% (w/v) fructose, also the highest EPS production was found in 2.5% (w/v) molasses. The strain 7055 was found to contain (98.6%) galactose and (1.4%) glucuronic acid in control medium whereas the composition of the strain 7055 (2.5% (w/v) fructose) was found to be (99.9%) neutral sugar and (0.1%) Glucuronic acid while the strain 7055 (2.5% (w/v) molasses) was found to contain (65.9%), neutral sugars and (34.1%) glucuronic acid
Effect of semi-solid reciprocating extrusion on microstructure and properties of Al2O3p/7055 composites
No full textSemi-solid reciprocating extrusion technique has been proposed to successfully prepare in-situ nano-Al2O3 particle reinforced 7055 aluminum matrix composites from Al–ZnO reaction system. It is demonstrated that the distribution of Al2O3 particles in the matrix is improved and the matrix grains are refined significantly via semi-solid reciprocating extrusion. After 2 extrusion passes, the average grain size of the matrix was reduced to 17.34 μm, the density of the composite increased to 98.9 %, and the Al2O3 particles in the matrix exhibited the most uniform distribution. After forging and heat treatment, the density of Al2O3p/7055 composite with 2 passes of semi-solid reciprocating extrusion increased to 99.2 %. The composite achieved a tensile strength of 631.2 MPa and a Vickers hardness of 201.5 HV, which are 10.3 % and 17.9 % higher than those of 7055 aluminum alloys, while also 13.8 % and 67.5 % higher than those of composites without semi-solid reciprocating extrusion
Effect of Pre-Stretching on Microstructures and Mechanical Behaviors of Creep-Aged 7055 Al Alloy and Its Constitutive Modeling
No full textThe rational pre-stretching can contribute to obtaining better mechanical properties. This paper studies the effect of creep stain, mechanical properties, and microstructures of 7055 alloy under different pre-stretching conditions. The results show that compared with solid-quenched alloy, the 7055-T6 alloy is the optimal scheme to attain more creep strain, and the range of pre-stretching from 1.6% to 3.3% is suitable for creep-aged 7055-T6 alloy to obtain better mechanical properties. Further examination by TEM test shows that pre-stretching promotes the formation of dislocations, which provides superior nucleation regions for ή phase resulting in a higher strength alloy. Meanwhile, a unified creep-aging constitutive model for 7055-T6 alloy is established which can be used to accurately predict its creep behavior under the different pre-stretching
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