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Properties–microstructure relationship in Al–Fe in situ composite produced by friction stir processing

Najafi, A ; Sharif University of Technology | 2019

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  1. Type of Document: Article
  2. DOI: 10.1177/1464420718803752
  3. Publisher: SAGE Publications Ltd , 2019
  4. Abstract:
  5. Effects of Fe particle volume percent (from 0 to 5%) and changing the tool rotation direction in each pass were studied on the microstructure evolution and mechanical properties of the in situ Al/intermetallic composites produced by three passes friction stir processing (FSP) with ∼10 µm Fe particles. Optical and scanning electron microscopes were used for the investigation of the composite homogeneity, formation of Al–Fe intermetallic compounds, and fracture surfaces. Tensile and microhardness tests were also carried out to evaluate the mechanical properties of the composites. Solid-state reactions between the aluminum matrix and Fe particles led to in situ formation of Al3Fe and Al5Fe2 intermetallics in the composite. Changing the tool rotation direction in each pass reduced asymmetrical distribution of the reinforcing particles and resulted in better dispersion of Fe particles. Increase in the particle volume percent refined the composite average grain size from ∼35 μm in the sample processed without particles to ∼6 μm in the composite included 5 vol.% of the Fe particles. Zener limiting grain size relationship was used to estimate the volume fraction of the sub-micron particles in the composites. Enhancement of the reinforcing particle volume percent (to 5%) increased ultimate tensile strength and yield strength of the composite up to ∼60% and ∼95%, respectively, due to finer grain structure as well as the higher load-bearing capacity of the Fe and intermetallic reinforcing particles compared to the aluminum matrix. Contributions of the Hall–Petch effect and the other strengthening mechanisms in the yield strength of the composites were also investigated. © IMechE 2018
  6. Keywords:
  7. Friction stir processing ; Hall–Petch relationship ; In situ composite ; Intermetallic compound ; Mechanical property ; Zener limiting grain size ; Aluminum ; Aluminum alloys ; Binary alloys ; Friction ; Friction stir welding ; Grain size and shape ; Intermetallics ; Iron compounds ; Mechanical properties ; Microstructure ; Reinforcement ; Scanning electron microscopy ; Solid state reactions ; Tensile strength ; Yield stress ; Asymmetrical distributions ; In-situ composite ; Limiting grain sizes ; Micro-structure evolutions ; Reinforcing particles ; Strengthening mechanisms ; Ultimate tensile strength ; In situ processing
  8. Source: Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 233, Issue 10 , 2019 , Pages 1955-1965 ; 14644207 (ISSN)
  9. URL: https://journals.sagepub.com/doi/abs/10.1177/1464420718803752