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The effect of annealing on microstructural stability, precipitate evolution, and mechanical properties of cryorolled (CR)
Al 7075 alloy was investigated in the present work employing hardness measurements, tensile test, X-ray diffraction (XRD),
differential scanning calorimetry (DSC), electron backscattered diffraction (EBSD), and transmission elec...
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... influence of annealing on mechanical properties of CR Al 7075 alloy at temperatures in the range of 323 K to 673 K (50 °C to 400 °C) was studied by employing tensile and hardness tests. The tensile prop- erties of CR Al 7075 alloy samples at different annealing temperatures are shown in Figure 6 and Table I. During ...
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... Indeed, post-processing after cryorolling has emerged as a promising approach for tailoring mechanical properties by manipulating the microstructure in a controlled manner [63]. Jayaganthan et al. [64] investigated the impact of annealing on the microstructural stability, precipitate evolution, and mechanical properties of the cryorolled Al 7075 alloy. Their findings revealed the onset of recrystallization at 150 • C, with completion at 250 • C. Notably, the ultrafine-grained microstructure of cryorolled Al 7075 exhibited thermal stability up to 350 • C. Consequently, annealing at 150 • C (423 K) led to a gradual increase in yield strength and ultimate tensile strength, accompanied by a sudden rise in ductility from 150 • C to 250 • C. Similarly, D. Singh et al. [65] studied the effect of annealing on the microstructure and mechanical properties of cryorolled Al 6061. ...
The quest for lightweight, high-performance structural materials for demanding applications such as in the fields of automotive, aerospace, and other high-tech and military industries pushes the boundaries of material science. The present work aims to draw attention to a novel, sustainable manufacturing approach for the development of next-generation 7xxx series aluminum alloys that have higher strength by rejuvenating a sustainable compositional and thermomechanical processing strategy. Our innovative strategy integrates two key synergies: trace hafnium (Hf) addition for microstructural refinement, unique thermomechanical treatment involving cryorolling, and a short annealing method. Experimental results revealed that our base alloy exhibited a 33 µm grain size and impressive initial mechanical properties (334 MPa UTS, 150 HV). Adding 0.6 wt.% Hf and employing 50% cryorolling with short annealing led to a remarkable 10 µm grain size reduction and significant mechanical property leaps. The resulting alloy boasts a 452 MPa UTS and 174 HV, showcasing the synergistic advantageous effect of Hf and cryorolling plus annealing treatment. The developed alloys were compositional- and work hardening-dependent, leading to a rich mix of strengthening mechanisms. Optical and scanning electron microscopy reveal several intermetallic phases within the fcc matrix, wherein the Al3Hf phase plays a key role in strengthening by impeding dislocation movement. In addition to experimental results, a 12-full-factorial design experiment via ANOVA analysis was also utilized to validate the significant influence of Hf and cryorolling on properties with (p-values < 0.05). Among the different parameters, cryorolling plus annealing appeared as the most noteworthy factor, followed by the composition. Using the regression model, the ultimate tensile strength and hardness were predicted to be 626 MPa UTS and 192 HV for an alloy with 0.6 wt.% Hf and 85% cryorolling, which opens a new avenue for ultra-high-strength Al7xxx alloys.
... As shown here, the applied aging treatments for the AGR and OVGR specimens cause the formation of precipitates enriched with Mg and Zn. As reported before, the aging of the alloy at 473 K results in the precipitation of 0 while the aging at 573 K results in the precipitation of (Maloney et al., 1999;Nicolas & Deschamps, 2003;Ringer & Hono, 2000;Berg et al., 2001;Panigrahi & Jayaganthan, 2011). Considering the applied aging treatments before rolling, one can infer that the observed precipitates inside microstructures of AGR and OVGR specimens should be 0 and , respectively (Ringer & Hono, 2000;Panigrahi & Jayaganthan, 2011). ...
... As reported before, the aging of the alloy at 473 K results in the precipitation of 0 while the aging at 573 K results in the precipitation of (Maloney et al., 1999;Nicolas & Deschamps, 2003;Ringer & Hono, 2000;Berg et al., 2001;Panigrahi & Jayaganthan, 2011). Considering the applied aging treatments before rolling, one can infer that the observed precipitates inside microstructures of AGR and OVGR specimens should be 0 and , respectively (Ringer & Hono, 2000;Panigrahi & Jayaganthan, 2011). Also, one can see that the precipitates observed inside the microstructure of OVGR are coarser than those of AGR. ...
... Also, one can see that the precipitates observed inside the microstructure of OVGR are coarser than those of AGR. This effect is because of applying a higher aging temperature for the OVGR, which results in coarsening of the precipitates (Panigrahi & Jayaganthan, 2011). In addition, one may expect a considerable presence of GP zones inside the microstructure of SSR specimens since the GP zones appear after a few minutes of natural aging ( Appearance of precipitates inside the microstructure of (a) AGR and (b) OVGR before the rolling process. ...
Aluminium alloy 7005 is widely used for structural purposes because of its attractive properties such as good weldability and age-hardening capability. However, since the workability of this alloy falls after a short period of natural aging, the application of cold rolling for the production of strain-hardened sheets of this alloy is a challenge. Two solutions proposed to overcome this challenge are as follows: (a) immediate rolling of the alloy after solution treatment and (b) rolling of the alloy after artificial aging. However, there is no comprehensive study comparing the effect of pre-rolling aging treatments on the evolutions of microstructure and texture of the alloy through heavy cold rolling. This subject is the aim of the present study. For this purpose, different pieces of the alloy are subjected to three different heat treatments before rolling, and afterward, they are rolled to obtain a thickness reduction of 80%. Scanning electron microscopy with electron backscattered diffraction observations are applied to study the evolutions of the microstructure and the texture of the alloy. Results show that the progression of pre-rolling aging decreases the incidence of micro-scaled shear bands by rolling. In addition, the rolling texture intensity decreases with the advancement of pre-rolling aging. Mechanisms responsible for this effect are discussed.
... However, the FCG behavior of bulk UFG precipitation hardenable Al alloys deformed through other SPD methods is rare in the literature. These residues interact with the dislocations during the deformation and provide a strengthening effect, as reported [24][25][26]. The impact of precipitation on the monotonic strength properties of bulk U.F.G. ...
... The EN AW-7075 aluminium alloy is very susceptible to natural and artificial ageing treatments so properties of this alloy can be enhanced by precipitation hardening. The largely accepted precipitation sequence for this alloy can be presented as: α ssss → GP zones → metastable η' phase → stable η phase (Panigrahi and Jayaganthan, 2011;Kacar and Guleryuz, 2015;Choi et al., 2015;Ozer and Karaaslan, 2017;Kilic et al., 2019;Cai et al., 2020). During the research of different mechanical properties, the authors focus on achieving the precipitation of a metastable η' phase. ...
... Nicolas (2002) stated in his dissertation that this phase can be presented as MgZn 2 , but there is a strong possibility for copper to be present in this so-called η' phase. Many authors have focused their research on the mechanical properties of the EN AW-7075 aluminium alloy during different heat treatments (Panigrahi and Jayaganthan, 2011;Fallahi et al., 2013;Kacar and Guleryuz, 2015;Chen et al., 2015;Ozer and Karaaslan, 2017;Ku et al., 2018;Kilic et al., 2019;Cai et al., 2020). Kacar and Guleryuz (2015) showed that the quench rate, pre-straining as well as the ageing temperature and time, play an important role in the precipitation hardening. ...
... From the Fig. 1, it can be seen that one wide peak appears at around 200 °C. Based on the literary data (Panigrahi and Jayaganthan, 2011;Ku et al., 2018;Hebbar et al., 2020) and the appearance of one wide DTA peak at around 200 °C, it can be concluded that this peak represents the precipitation range of the metastable η' phase. Due to the wideness of the peak, it can be assumed that some other phases will precipitate in that temperature range, i.e., GP zones (a tempera- The quenched sample was characterized using differential thermal analysis (DTA) using the SDT Q600 (TA Instruments) analyser with heating rate of 10 °C·min −1 up to 450 °C. ...
The influence of the ageing temperature on the hardness, electrical conductivity, thermal diffusivity and thermal conductivity of the EN AW-7075 aluminium alloy was studied in this paper. After solution treating the alloy at 480 °C for 1 h and quenching it in ice water, the investigated alloy was characterized using Differential Thermal Analysis (DTA) in order to determine the optimal temperatures for the isochronal ageing treatments. Afterwards, isochronal ageing was conducted at the temperature range of 110 °C-250 °C for 30 min The hardness, electrical conductivity, thermal diffusivity, thermal conductivity and microstructural features were investigated during the ageing treatments. Hardness had a peak value after ageing at 150 °C, while other properties gradually increased with the ageing temperature. Microstructural investigation of the aged alloy by SEM-EDS revealed the existence of precipitated phases that appear homogenously distributed in the microstructure.
... The major alloying elements of the precipitation-hardening aluminum alloy AA7075 are Zinc (5.1-6.1 wt.%), Magnesium (2.1-2.9 wt.%), and Copper (1.2-2.0 wt.%). Due to their very high strength to weight ratio, the AA 7075 alloy is widely utilized in the structural components of aircraft and the automobile industry [3][4][5]. Since Al 7XXX series is a heat-treatable alloy, and in order to enhance the formability and ductility, and to stabilize the microstructure of the Al 7075 alloy, a proper and effective annealing treatment is required and very important [3,5,6]. Three different types of second phase particles, including (intermetallic particles made from elements like Zr, Cr, and Mn), constituents (Fe or Si impurities, or excessive amount of major elements), and strengthening precipitates (MgZn2) can be found in the microstructure of the AA 7075 [5,7]. ...
... Due to their very high strength to weight ratio, the AA 7075 alloy is widely utilized in the structural components of aircraft and the automobile industry [3][4][5]. Since Al 7XXX series is a heat-treatable alloy, and in order to enhance the formability and ductility, and to stabilize the microstructure of the Al 7075 alloy, a proper and effective annealing treatment is required and very important [3,5,6]. Three different types of second phase particles, including (intermetallic particles made from elements like Zr, Cr, and Mn), constituents (Fe or Si impurities, or excessive amount of major elements), and strengthening precipitates (MgZn2) can be found in the microstructure of the AA 7075 [5,7]. ...
... Researchers have worked on heat treatment of AA 7075. Panigrahi and Jayaganthan [3] studied the effect of cryorolling for AA 7075 followed by annealing treatment. They found that the tensile strength and hardness of the CR Al 7075 alloys reduced during the annealing treatment process from 150 to 250°C and for subsequent it remains constant. ...
The current study examined how the annealing process affected the formability, mechanical and chemical characteristics of 7075 alloy. The formability was achieved during the bending test. Tensile, hardness, microstructure and corrosion tests represent mechanical and chemical properties. The test specimens for each test were prepared then followed by annealing heat treatment by heating them to 200 and 300°C in an electrical furnace for two hours. Then, the specimens were allowed to cool in the furnace to a room temperature. The results indicate that the tensile strength and hardness were decreased for about 50%. Bending strength was increased by approximately 30%, where the specimens bent at a very high angle without cracking or breaking in comparison to base metal. Annealing heat treatment with a proper selected procedures and temperatures was able to stabilize the microstructure and release the second phase precipitate particles. Annealing process contributed in improving formability, ductility and corrosion resistance of the Al 7075 alloy. This is an open-access article under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/) Publisher : Middle Technical University
... The fraction of recrystallization can be calculated in terms of hardness measurements by using Eq. (7) as follows [45]: ...
In this study, an investigation was conducted over the effect of annealing on microstructure and precipitation evolution, microhardness, thermal stability, as well as grain growth kinetics of Al 7075 alloy processed by cryogenic temperature extrusion machining (CT-EM). A severely deformed microstructure with refined grains and high dislocation density was obtained in the initial CT-EM sample. There was an improvement in the hardness of the chip sample due to the precipitation strengthening in the case of sample annealed at 150 °C, when the dislocation density decreased. With the increase of the annealing temperature, more dislocation-free equiaxed grains were present in the microstructure. The recrystalliza-tion process started at 150 °C and got completed at 300 °C. The ultrafine grained (UFG) Al 7075 alloy fabricated by CT-EM was thermally stable up to 350 °C, which could be attributed to the pinning effect of precipitates. The differential scanning calorimeter (DSC) results indicated the efficiency of CT-EM treatment in facilitating precipitate kinetics. The activation energy of grain growth in the Al 7075 alloy subjected to CT-EM was higher than that of materials processed by other severe plastic deformation (SPD) processes.
... However, the coarsening and dissolution of the reinforced precipitation phase caused a significant decrease in microhardness [41,42]. The rapid decrease in the microhardness of the sample after the thermal load treatment at 230 • C indicated that the material exhibited a softening effect [43]. The formation of low-dislocation recrystallized grains further improved the softening effect of the metal [44]. ...
The rolling correction process can eliminate machining distortions of aluminum alloy 7075-T651 structural parts. The thermal stability of the corrected structural parts under the action of temperature loading, especially the macroscopic shape stability, is key to ensure the safe service of mechanical equipment. In this study, different thermal loads were used to postprocess aluminum alloy 7075-T651 structural parts after rolling correction. The thermal stability of the rolled samples was analyzed by characterizing the microstructure and physical and mechanical properties. The results show no obvious change compared to rolling in the distortion of the parts after temperature treatments at 120 °C, 160 °C, 230 °C and 300 °C; the distortion changes were only 10.48%, 2.74%, 8.13% and 8.70%, respectively. The residual stresses in the rolling areas of the samples decreased by 35.58%, 26.08%, 75.97% and 83.13%, respectively. The microhardness also showed a decreasing trend. There was no obvious change after treatment at 120 °C, but the hardness decreased by approximately 5%, 23% and 56%, respectively, after treatments at other temperatures. However, the rolling stress relaxed under thermal stress. The microstructure change analysis shows that the material microstructure is mainly dominated by static reversion at lower thermal loads. With increasing thermal load, the samples are mainly affected by the static recrystallization effect, the microstructure is gradually blurred, and the hardness decreases significantly. In conclusion, although the residual stresses introduced by rolling would occur in different degrees of stress relaxation under the thermal load, the microstructure changes caused by thermal load did not significantly affect the macroscopic distortion of the samples, and the macroscopic shape of the structural parts after rolling correction had good thermal stability.
... The CR methodology provides the path for advanced cold surface hardening production line used in the industrial context [18]. At cryogenic temperatures, Al alloys have a high ductility [19]. For the production of UFG/NG Al alloys, CR has a broad range of applications. ...
The demands for lightweight automotive parts are increasing tremendously in the industry. Most of these parts are produced using metal forming processes in order to gain parts that has lightweight, good strength and rigidity. Most of the rolling processes are used to improve ductility and the strength of the material the rolling surface is modified through introduction of an additional step of cross-rolling during the deformation. The mechanical and the microstructure characteristics have been review in this article. The article imposing on the present scenario, last developments and upcoming future directions on topics. This article has been made an attempt to equate the performance of different rolling processes (i.e. Room Temperature Rolling, Cryo rolling, Cryo cross Rolling, Asymmetric Cryorolling) on the material, in the literature.
... In the literature, the hardness value of Al7075 alloy without T6 treatment has been reported as ~71 HV [29]. [30]. In the present study, an increase in the hardness was observed in the nitrided sample in comparison with the sample with the removed nitride layer. ...
z Al7075 alloy is commonly used in the automotive industry, components of military vehicles and aircraft, rubber and plastic moulds. Also, similar Al alloys are frequently used for mechanical parts in space exploration. Therefore, investigation of the wear properties under a vacuum environment is as indispensable as wear properties under an atmosphere. However, the wear performance of this alloy cannot meet the expectations. This paper reports the investigation of the obtained wear properties of Al7075-T6 alloy after plasma nitriding in ambient air and vacuum environments. The surface characterization and phase analysis of the formed AlN layers are determined by scanning electron microscope, energy dispersive X-ray spectrometer, 3D optical profilometer and X-ray diffractometer. The hardness of the nitride layer is established using Vickers micro-hardness tester. The wear performance of the untreated and nitride sample is investigated under 1N constant load at ambient air and vacuum environment. As a result of wear tests, the best wear performance of both conditions has been obtained from nitrided samples. The AlN layer (0.19) is observed to notably reduced the coefficient of friction of the substrate (0.60) under ambient air. Besides, it is observed that the nitride layer is better in ambient air (0.00010 mm 3 /Nm) than in vacuum environment (0.00087 mm 3 /Nm) in term of wear rate. In fact, the wear track on the nitrided sample is very thin under ambient air, and nearly imperceptible. Al7075 alaşımları, otomotiv endüstrisinde, askeri araçların ve uçakların bileşenlerinde, kauçuk ve plastik kalıplarda yaygın olarak kullanılmaktadır. Ayrıca, benzer Al alaşımları, uzay araştırmalarında mekanik parçalar için sıklıkla kullanılmaktadır. Bu nedenle, vakum altında aşınma özelliklerinin incelenmesi, atmosfer ortamındaki aşınma özellikleri kadar vazgeçilmezdir. Ancak söz konusu alaşımların aşınma performansı beklentileri karşılayamamaktadır. Bu bağlamda, bu çalışmada nitrürlenmiş Al7075-T6'nın atmosfer ve vakum ortamlarında aşınma özelliklerinin belirlenmesi amaçlanmıştır. Oluşturulan AlN tabakasının yüzey karakterizasyonu ve faz analizi, taramalı elektron mikroskobu, enerji dağıtıcı X-ışını spektrometresi, 3D optik profilometre ve X-ışını difraktometresi ile belirlenmiştir. Numunelerin sertliği, Vickers mikro sertlik test cihazı kullanılarak belirlenmiştir. Numunelerin aşınma performansı, bilye disk esaslı aşınma test cihazı kullanılarak atmosfer ve vakum ortamlarında incelenmiştir. Her iki koşul için de en iyi aşınma performansı nitrürlenmiş numunelerden elde edilmiştir. AlN tabakasının (0,19), ortam havası altında alt tabakanın (0,60) sürtünme katsayısını önemli ölçüde azalttığı gözlemlenmiştir. Nitrür tabakası sayesinde, alaşımın atmosfer ortamındaki aşınma direnci dikkate değer bir şekilde iyileştirilmiştir. Ayrıca aşınma oranı açısından nitrür tabakasının aşınma performansı, ortam havasında (0.00010 mm 3 /Nm) vakum ortamına (0.00087 mm 3 /Nm) göre daha iyi olduğu gözlemlenmiştir. Hatta numunelerdeki aşınma yolunun çok ince olduğu ve neredeyse fark edilemez olduğu gözlemlenmiştir.
... In the present study, solution heat treatment parameters of all conditions were equal. During solution heat treatment of EN AW 7075, high-angle and low-angle grain boundaries as well as dislocations can be pinned based on the Zener pinning mechanism, at least prior to dissolution of precipitates [44,45]. Migration of low-angle boundaries and annihilation of point defects and dislocations are known to be the main mechanisms in case of recovery of aluminum alloys [46,47]. ...
In the present study, microstructural and mechanical properties of EN AW 7075 following stress-aging were assessed. For this purpose, properties of stress-aged samples were compared with values obtained for conventionally aged counterparts. It is revealed that the strength and hardness of EN AW 7075 can be increased by the presence of external stresses during aging. Precipitation kinetics were found to be accelerated. The effects of conventional and stress-aging on the microstructure were analyzed using synergetic techniques: the differently aged samples were probed by differential scanning calorimetry (DSC) in order to characterize the precipitation processes. DSC was found to be an excellent screening tool for the analysis of precipitation processes during aging of this alloy with and without the presence of external stresses. Furthermore, using electron microscopy it was revealed that an improvement in mechanical properties can be correlated to changes in the morphologies and sizes of precipitates formed.
