Effect of annealing treatment on microstructure and fatigue crack growth behavior of Al–Zn–Mg–Sc–Zr alloy

Al–Zn–Mg–Sc–Zr alloy samples were annealed to four different states (under-aging, peak-aging, over-aging and double-aging) and then thoroughly investigated by means of electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile and fat...

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Bibliographic Details
Published in:Journal of Central South University 2018-05, Vol.25 (5), p.961-975
Main Authors: Chen, Jing, Pan, Qing-lin, Yu, Xue-hong, Li, Meng-jia, Zou, Hao, Xiang, Hao, Huang, Zhi-qi, Hu, Quan
Format: Article
Language:English
Subjects:
Aging
Aging (metallurgy)
Annealing
Bifurcations
Crack propagation
Electron backscatter diffraction
Engineering
Fatigue failure
Fatigue tests
Fracture mechanics
Growth rate
Magnesium
Metallic Materials
Microscopy
Microstructure
Scandium
Scanning electron microscopy
Tensile properties
Transmission electron microscopy
Yield strength
Zinc
Zirconium
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Summary:Al–Zn–Mg–Sc–Zr alloy samples were annealed to four different states (under-aging, peak-aging, over-aging and double-aging) and then thoroughly investigated by means of electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile and fatigue crack growth rate tests to explore the influence of annealing treatment on microstructure and fatigue crack growth behavior. The results indicate that Al 3 (Sc,Zr) particles can effectively refine grains and enhance tensile properties and fatigue properties. After annealing treatment, the under-aged sample and double-aged sample obtained average grain sizes of 4.9473 and 4.1257 μm, and the maximum value of yield/tensile strength (561 MPa/581 MPa) was obtained in peak-aged state. In the Paris region, fatigue crack growth rate, crack deflection and bifurcation, crack blunting and inter/trans-granular propagation were discussed based on data fitting and Laird model and Griffith theory. And the results show that the under-aged sample possesses the best resistance to fatigue crack propagation and the most tortuous and bifurcated crack path. For all samples, the fatigue crack growth rate in the rupture region was inversely proportional to yield strength.
ISSN:2095-2899
2227-5223
DOI:10.1007/s11771-018-3797-5