On the low-cycle fatigue behavior of thermo-mechanically processed high-strength aluminum alloys

Sajadifar, Seyed Vahid; Scharifi, Emad; Wegener, Thomas; Krochmal, Marcel; Lotz, Steffen; Steinhoff, Kurt; Niendorf, Т.

doi:10.1016/j.ijfatigue.2021.106676

Cited by 17 publications

(16 citation statements)

References 72 publications

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“…Moreover, small numbers of microcracks were initiated at the machining defects on the specimen surface. Upon microcrack initiation under cyclic loading (Figures 10a,c and 11a,c), the fatigue microcrack propagated along the perpendicular direction to the maximum stress axis and fanned out from the step of the fatigue microcrack initiate site before expanding forward until the occurrence of specimen fracture [35][36][37]. In high-magnification images, the fatigue microcracks were initiated on the secondary surface with coarse second phases since the second phase particles with insoluble Ce-rich rare earth compounds and iron-containing intermetallic compounds could cause stress concentration during the fatigue testing (Figures 10b,d and 11b,d), resulting in particles fragmentation, detachment, and initiation of microcracks [38][39][40].…”

Section: High Cycle Fatigue Performance Of 211zx Alloymentioning

confidence: 99%

Effect of Microstructure on High Cycle Fatigue Behavior of 211Z.X-T6 Aluminum Alloy

Zhong

Huang

Chen

et al. 2022

Metals

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In the present paper, the high cycle fatigue (HCF) of a novel 211Z.X aluminum alloy with high strength was studied under hot-rolling and as-cast states at room temperature. The effects of microstructure and distribution of precipitated phases and impurities on the mechanical properties, HCF performances, fatigue microcrack initiation, and propagation behavior of the 211Z.X alloy were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The HCF S–N curves, P–S–N curves and Goodman fatigue diagrams of 211Z.X alloy consisting of two microstructures were drawn. The results suggested that the fine and dispersive distribution of the second phases improved the strength of the alloy. The formation of short-bar and spherical precipitates promoted coordinated deformation of the alloy. This promoted higher microcrack initiation resistance of 211Z.X alloy with a hot rolling state than in the cast state. As a result, the HCF properties of the hot-rolling alloy were better than those of the cast alloy. In sum, these results look promising for future reliable design of engineering structures and application of new aluminum alloys.

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Section: High Cycle Fatigue Performance Of 211zx Alloymentioning

confidence: 99%

Effect of Microstructure on High Cycle Fatigue Behavior of 211Z.X-T6 Aluminum Alloy

Zhong

Huang

Chen

et al. 2022

Metals

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“…The formation of fine and dispersed precipitates promotes low interparticle spacing. Low interparticle spacing is a key element in the strengthening of high‐strength aluminum alloys since dislocation motion can be considerably impeded due to the dislocation–precipitate interactions [45, 47]. However, coarse precipitates are formed in the vicinity of grain boundaries after the employment of low cooling rates as schematically shown.…”

Section: Resultsmentioning

confidence: 99%

“…Another detail present on the fracture surfaces of different specimens is the trace of the de-cohesion of coarse particles from the matrix. Weak precipitates/matrix interfaces provide suitable sites for crack initiation [45,46]. The size of these particles is larger for the specimens quenched in the air compared to other conditions.…”

Section: Fractographymentioning

confidence: 99%

Cooling rate as a process parameter in advanced roll forming to tailor microstructure, mechanical and corrosion properties of EN AW 7075 tubes

Sajadifar

Suckow

Heider

et al. 2022

Materialwissenschaft Werkst

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The effects of solution heat treatment parameters and quench media as a processing tool for tailoring microstructure, mechanical and corrosion properties in roll forming of EN AW 7075 alloy were studied. The highest yield stress and ultimate tensile strength were obtained for the specimens quenched in water, while the air‐cooled specimens exhibited inferior mechanical properties. Microstructural analysis of specimens showed that except water‐quenched specimens, the parts cooled/quenched in oil, in direct contact with tool steel and air are characterized by coarse precipitates and precipitate‐free zones. The corrosion tests showed that the cooling rate has a pronounced influence on the corrosion resistance and related mechanism of EN AW 7075 alloy. The surfaces of specimens quenched in water remained intact although pitting corrosion took place. The microstructure of the part processed by roll forming was explored in direct comparison. It is revealed that by the employment of quenching nozzles, a high cooling rate similar to the water‐quenched condition can be achieved. Results obtained in the present study pave the way to directly tailor aluminum parts for specific applications.

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“…The formation of coarse precipitates leads to large interparticle spacing. [28,29] As a result of large interparticle spacing, dislocation motions can occur with less resistance during further deformation/loading of the material, eventually degrading the strength and hardness of components. Low strengths and hardness values obtained for all samples (even for the sample formed for 8 s on the cooled side of the tool following water cooling) already indicate that the interparticle spacing should be relatively large.…”

Section: Microstructure Analysismentioning

confidence: 99%

Functionally Graded AA7075 Components Produced via Hot Stamping: A Novel Process Design Inspired from Analysis of Microstructure and Mechanical Properties

et al. 2023

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Herein, functionally graded AA7075 components manufactured via hot stamping are investigated by focusing on the effect of different process variables on localized microstructure evolution. To realize gradation through stamping, an active tool is designed and applied. The design of experiments allows to assess the impact of transfer time from the furnace to the tool, quenching time in the tool, and final quenching media. Related characteristics of mechanical properties throughout the hat‐shaped profile are assessed via hardness and tensile tests. As expected, the sections of the samples formed in the cooled part of the tool are characterized by higher mechanical strength following subsequent aging, while sections formed in the heated part exhibit higher ductility. Moreover, the microstructural analysis reveals that fine precipitates with minimum interparticle distances only form in the cooled section of the samples. Increasing the tool temperature at the heated side to 350 °C results in the formation of coarse precipitates in the grain interior and along the grain boundaries. A sharp gradient in terms of microstructural and mechanical properties is found between these conditions. After reducing the transfer time, an increased volume fraction of fine precipitates leads to further improvements in hardness and mechanical strengths.

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On the low-cycle fatigue behavior of thermo-mechanically processed high-strength aluminum alloys

Cited by 17 publications

References 72 publications

Effect of Microstructure on High Cycle Fatigue Behavior of 211Z.X-T6 Aluminum Alloy

Effect of Microstructure on High Cycle Fatigue Behavior of 211Z.X-T6 Aluminum Alloy

Cooling rate as a process parameter in advanced roll forming to tailor microstructure, mechanical and corrosion properties of EN AW 7075 tubes

Functionally Graded AA7075 Components Produced via Hot Stamping: A Novel Process Design Inspired from Analysis of Microstructure and Mechanical Properties

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