Effect of Two-Stage Double Peak Aging on Microstructure and Properties in 7050 Aluminum Alloy

2012 ◽  
Vol 157-158 ◽  
pp. 331-337 ◽  
Author(s):  
Chang De He ◽  
Jian Ping Ren ◽  
Bing Xu
Keyword(s):  
Aluminum Alloy ◽  
Aging Process ◽  
High Density ◽  
Age Hardening ◽  
Strengthening Effect ◽  
Two Stage ◽  
Double Peak ◽  
7050 Aluminum Alloy ◽  
Peak Aging ◽  
Better Than

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.

Natural Aging Behavior of Double-Sided MIG Welded A7N01-T5 Aluminum Alloy

2018 ◽  
Vol 941 ◽  
pp. 1155-1160
Author(s):  
Ying Li ◽  
Zhi Qiang Zhang ◽  
Jian Liu ◽  
Hua Yin ◽  
Chang Shu He
Keyword(s):  
Aluminum Alloy ◽  
High Speed ◽  
Aging Process ◽  
Weld Zone ◽  
Natural Aging ◽  
Middle Layer ◽  
Age Hardening ◽  
Aging Behavior ◽  
Epma Analysis ◽  
Zn Content

A heat treatable A7N01 (Al-Zn-Mg) aluminum alloy mainly used to fabricate high-speed train body structures was double-sided welded by MIG welding. The natural aging behavior of the joint was systematically studied by local and global mechanical property testing method. Based on TEM observation and EPMA analysis, the key factors that lead to different natural aging behavior among various regions of the joint were discussed. The global tensile strength of the joints increased obviously after natural aging. All the joint samples fractured in the weld zone, which demonstrated the weld zone was the weakest zone of the joints. And the strength of the global welds were depended on the microstructure and natural aging ability of the weld zone. Moreover, the increase of the tensile property of the three local regions in the weld zone after post natural aging decreased as Middle>lower>upper. The above phenomenon was also further confirmed by microhardness measurement. The age hardening behavior is greatly influenced by the concentration of strengthening precipitates forming element Zn. The Zn content in the weld zone determined by EPMA showed that element Zn was dispersed unevenly, which is attributed to the double V-groove design used in this work and Zn vaporization in the molten pool during welding. The Zn content in the middle layer metals is higher than that of the upper and lower layers, resulting in the remarkable hardening response for the middle layer of the weld zone during natural aging process. Additionally, the solution zone containing the same Zn content as the base metal and undergoing sufficient solid solution during welding was found to possess the high hardening ability after natural aging process.

Age Hardening Behavior in Al-8Zn-2Mg-2Cu Wrought Aluminum Alloy

2012 ◽  
Vol 710 ◽  
pp. 527-532
Author(s):  
V. Anil Kumar ◽  
Raghavendra R. Bhat ◽  
Romesh C. Sharma
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Aging Time ◽  
Large Scale ◽  
Aluminum Matrix ◽  
High Strength ◽  
Age Hardening ◽  
Stable Phase ◽  
Conductivity Measurements ◽  
Peak Aging

Aluminum alloys based on Al-Zn-Mg-Cu system classified under high strength light alloys, find a large scale application in aerospace sector. In the present study, heat treatment of an Aluminum alloy with Al-8Zn-2Mg-2Cu wt.% (AA7449) was carried out. Heat treatment parameters were optimized based on hardness and conductivity measurements. The mechanisms of strengthening in primary and secondary aged states are explained using hardness and conductivity measurements. Conductivity generally showed an increasing trend with increase in aging time, which could be attributed to decrease in the lattice distortion of the Aluminum matrix with increase in aging time. The dissolution of GP zones and formation of other metastable phases like η’ and stable phase like η were found to reduce the supersaturation in the matrix as the precipitation growth and coarsening processes are completed during overaging. Transmission electron microscopy (TEM) study was carried out to confirm the peak-aging regime. Selected Area Diffraction (SAD) patterns were recorded where GP zones and η’ precipitates were observed in the bright field images to establish their nature. The mechanical properties were correlated with the TEM observations and was suggested that a critical distribution of GP zones and η’ precipitates is essential to achieve peak strength in Al-Zn-Mg alloys.

scholarly journals The Effect Of Two-Stage Age Hardening Treatment Combined With Shot Peening On Stress Distribution In The Surface Layer Of 7075 Aluminum Alloy

2015 ◽  
Vol 60 (3) ◽  
pp. 1993-1998 ◽  
Author(s):  
Ł. Kaczmarek ◽  
P. Zawadzki ◽  
M. Stegliński ◽  
R. Wójcik ◽  
M. Klich ◽  
...  
Keyword(s):  
Surface Layer ◽  
Aluminum Alloy ◽  
Stress Distribution ◽  
Shot Peening ◽  
Age Hardening ◽  
7075 Aluminum Alloy ◽  
Two Stage ◽  
Compressive Stresses ◽  
Hardening Treatment ◽  
Thermo Mechanical Treatment

Abstract The article present the results of the study on the improvement of mechanical properties of the surface layer of 7075 aluminum alloy via two-stage aging combined with shot peening. The experiments proved that thermo-mechanical treatment may significantly improve hardness and stress distribution in the surface layer. Compressive stresses of 226 MPa±5.5 MPa and hardness of 210±2 HV were obtained for selected samples.

Effect of Cold Deformation on Precipitation of 7050 Aluminum Alloy during Aging Process

2015 ◽  
Vol 1120-1121 ◽  
pp. 1014-1018
Author(s):  
Hong Wei Yan ◽  
Liang Zhen ◽  
Jian Tang Jiang
Keyword(s):  
Electron Microscopy ◽  
Aluminum Alloy ◽  
Aging Process ◽  
Cold Deformation ◽  
Research Topic ◽  
Strengthening Mechanisms ◽  
Scanning Calorimetry ◽  
Main Research ◽  
Transmission Electron ◽  
7050 Aluminum Alloy

Strengthening of aluminum alloy has always been an interesting research topic. There might be interactions between different strengthening mechanisms. In this paper, the effect of large cold deformation on the precipitation of as-quenched 7050 aluminum alloy was studied. Differential scanning calorimetry was used as the main research technique, accompanied by tensile test and transmission electron microscopy. It was found that clusters and precipitation had formed in the cold deformation, and dislocations accelerated the precipitation dynamics.

Influence of Three-Step Aging Heat Treatment on Properties of 7A04 Aluminum Alloy

2011 ◽  
Vol 704-705 ◽  
pp. 645-649
Author(s):  
Qiu Ze Li ◽  
Lei Xu ◽  
Ji Xiao Song ◽  
Jing Han ◽  
Xing Min Huang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Aging Process ◽  
High Strength ◽  
Aging Heat Treatment ◽  
Peak Aging ◽  
Low Temperature Aging ◽  
Mechanical Properties And Corrosion ◽  
Temperature Aging

Aiming at traditional peak aging of 7A04 Aluminum Alloy with high strength but low corrosion resistance, innovative gradually cooling three-step aging heat treatment process were designed, conventional mechanical properties and corrosion resistance of 7A04 aluminum after three kinds of aging treatments was studied through microstructure. The results show that compared with the traditional peak aging process, two gradually cooling three-step aging process is to improve materials tensile strength, plastic and impact toughness in different degrees. Meanwhile corrosion resistance of materials has improved significantly. And extension of low temperature aging time is conducive to the further improvement of strength.

Effect of Secondary Aging Process on the Structure and Properties of 7050 Aluminum Alloy Forging

2020 ◽  
Vol 861 ◽  
pp. 57-64
Author(s):  
Wei Wei He ◽  
Min Hao ◽  
Hui Qu Li ◽  
Liang Wang ◽  
Jun Zhou Chen
Keyword(s):  
Fracture Toughness ◽  
Aluminum Alloy ◽  
Electron Microscope ◽  
Aging Time ◽  
Aging Process ◽  
Fracture Mechanisms ◽  
Second Stage ◽  
7050 Aluminum Alloy ◽  
Stress Corrosion Resistance ◽  
Precipitation Phase

The effect of the second-stage aging process on the tensile properties, fracture toughness and electrical conductivity of 7050 aluminum alloy die forgings was studied, and the mechanism of strengthening and toughening was analyzed by transmission electron microscope and scanning electron microscope. The results show that with the extension of the second-stage aging time, the morphology of the precipitation phase remains unchanged, but the average radius of the precipitation phase and the distance between each other gradually increase. The fracture modes at this aging temperature are mixed fracture mechanisms of dimple fracture and intergranular fracture, and the number of dimple fractures increases with time. With the extension of the second-stage aging time, the strength of the alloy decreases, and the fracture toughness and stress corrosion resistance increase. The alloys heat-treated at 120°C×6 h +177°C×6~8 h two-stage aging process have excellent comprehensive properties.

scholarly journals Effect of Aging Treatment on the Corrosion Resistance Properties of 7N01 Extrusion Aluminum Alloy

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3615
Author(s):  
Yitai Li ◽  
Weiou Qin ◽  
Shuyuan Yu ◽  
Jun La ◽  
Yaokun Fu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Isothermal Aging ◽  
Room Temperature ◽  
Metastable Phase ◽  
Current Method ◽  
Single Peak ◽  
Two Stage ◽  
Eddy Current Method ◽  
Peak Aging

The influences of non-isothermal aging (the temperature range is 150–180 °C, and the heating rate is 5 and 20 °C/h alternately), single-peak aging (aging at 120 °C for 24 h, then water quenched was followed at room temperature), and two-stage aging (aging at 105 °C for 8 h first, then increasing aging temperature to 135 °C and keeping for 12 h, followed by water quenching at room temperature) on the corrosion resistance and microstructure of the 7N01 aluminum alloy under 3.5 wt.% NaCl were investigated using electric polarization curve test and exfoliation corrosion. After aging, the hardness of samples was measured by a Vickers micro-hardness tester, and the electrical conductivities were obtained using the eddy current method. The results show that the steady phase η and metastable phase η′ are precipitated in the grain boundary of 7N01 aluminum alloy after non-isothermal aging, and their distribution is discontinuous. The hardness of the alloy can reach 136.9 HV1 and the electrical conductivity can reach 35.8% IACS, which is close to the hardness of single-peak aging and the conductivity of two-stage aging, respectively. Compared with single-peak aging, the corrosion current density of non-isothermal aging is reduced by 15.5%, and that of two-stage aging is reduced by 28.9%.

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