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Fatigue fracture of friction-stir processed Al-Al3Ti-MgO hybrid nanocomposites

Sahandi Zangabad, P ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1016/j.ijfatigue.2016.02.007
  3. Publisher: Elsevier Ltd
  4. Abstract:
  5. This paper presents experimental results on the fatigue properties of Al-matrix nanocomposites prepared by the friction stir processing (FSP) technique. An Al-Mg alloy (AA5052) with different amounts (∼2 and 3.5 vol%) of pre-placed TiO2 nanoparticles were FSPed up to 6 passes to attain homogenous dispersion of nano-metric inclusions. Microstructural studies by electron microscopic and electron back scattering diffraction (EBSD) techniques showed that nano-metric Al3Ti (50 nm), TiO2 (30 nm), and MgO (50 nm) particles were distributed throughout a fine-grained Al matrix (<2 μm). Consequently, a significant improvement in the tensile strength and hardness was attained. Uniaxial stress-controlled tension-tension fatigue testing (R = 0.1) were utilized to evaluate the fatigue behavior of the prepared nanocomposites. The results were compared with the un-processed (annealed) and FSPed alloy without pre-placing TiO2 particles. It was found that FSP of the aluminum alloy increased the fatigue strength (at 107 cycles) for about 28% and 32% compared with the annealed specimen when the concentration of the reinforcing particles was 2 and 3.5 vol%, respectively. Fractographic analysis determined a ductile fracture behavior with deep-equiaxed dimples for the annealed and FSPed alloy. The facture surface of the nanocomposites revealed a combined ductile-brittle fracture mode with finer dimples. The mechanism of the fatigue fracture and the role of nano-metric inclusions were elaborated
  6. Keywords:
  7. Aluminum ; Fatigue ; Aluminum alloys ; Annealing ; Backscattering ; Brittle fracture ; Ductile fracture ; Fatigue of materials ; Fatigue testing ; Fractography ; Fracture ; Fracture mechanics ; Friction ; Friction stir welding ; Nanocomposites ; Tensile strength ; Titanium dioxide ; Tribology ; Electron back scattering diffraction techniques ; Fatigue properties ; Fractographic analysis ; Fracture behavior ; Friction stir processing ; Homogenous dispersions ; Hybrid nanocomposites ; Reinforcing particles ; Aluminum
  8. Source: International Journal of Fatigue ; Volume 87 , 2016 , Pages 266-278 ; 01421123 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S0142112316000529