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Interactive MENG 426 Lab Tutorials Experiment (8) Al-SiC MMC Microstructure

The American University in Cairo Mechanical Engineering Department MENG 426: Metals, Alloys & Composites. Interactive MENG 426 Lab Tutorials Experiment (8) Al-SiC MMC Microstructure. Prepared by Eng. Moataz M. Attallah Fall 2002. Outline. Introduction: Composite materials

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Interactive MENG 426 Lab Tutorials Experiment (8) Al-SiC MMC Microstructure

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  1. The American University in CairoMechanical Engineering DepartmentMENG 426: Metals, Alloys & Composites Interactive MENG 426 Lab Tutorials Experiment (8) Al-SiC MMC Microstructure Prepared by Eng. Moataz M. Attallah Fall 2002

  2. Outline • Introduction: Composite materials • Advantages of composites • Types of composites • Particulate reinforced MMC • Objectives • Specimen • Results

  3. Composite Materials (I) Definition • A complex solid material composed of two or more material classes by physical bonding, insoluble on the macroscopic scale to produce a material who has hybrid properties of the classes properties. • No Chemical Reaction • No Alloy forms (substitutional/interstitial) • Properties produced

  4. Composite Materials (II) • A composite is composed of a matrix, which completely surrounds the reinforcement (either in fiber, powder, or particulate form). • A coupling/bonding agent(binder) has to be used to bond the different classes together.

  5. Composite Materials (III) Matrix • Soft phase (ductility/formability/toughness) • Polymer/Ceramic/Metal Reinforcement • Hard phase (stiff/hard/not formable) • Discontinuous/Continuous • Oriented/Disoriented • Oxides/Carbides/Nitrides/Fibers/Whiskers/ Particulates.

  6. Mechanical Behavior

  7. Advantages of Composites • Higher specific stiffness • Higher specific strength • Corrosion resistance • Toughness (impact strength) • Heat deflection temperature • Mechanical damping • Design flexibility • Manufacturing economy

  8. Design Flexibility

  9. http://www.uweb.ucsb.edu/~jess28/F-117.jpg Improved Properties

  10. Classification of Composites • By Reinforcement (Fiber reinforced /Particulate /Dispersion) • By matrix (metal matrix/polymer/metal) • By manufacturing method

  11. Particulate Composites • Examples: carbides, SiCw/Al, filled polymers, glass ceramics. • Strengthening Mechanisms: Matrix contraction, Particle strength, Residual stress, Control flaw size, Microcracking, Transform tough, Crack bridging, Crack deflection. • Load bearing member: shared • Reinforcement characteristics: Large particles >1µm, typically (5-10µm) with 0.1 to .95 Vf

  12. Other Types • Fiber Composites GFRP, CFRP, SiC-Ti, SiC-Al, etc.. • Dispersed composites Age hardening alloys (experiment (#7))

  13. Particulate MMC • Properties depend on: 1. Particulate % 2. Size 3. Shape 4. Material

  14. Aluminum Matrix Composites Manufacturing Techniques • Solid State Process: Powder Metallurgy • Liquid State Process: squeeze casting/stir casting • Deposition processes

  15. Al-SiC MMC Microstructure

  16. Al-SiC MMC Applications

  17. Objectives • Understand the difference between a monolithic and a composite material • Understand the effect of the particle volume fraction on the mechanical properties and microstructure of a MMC • Pinpoint the defects & inhomogeneities in the composite structure

  18. Sample Preparation • Weigh powders acc. to fractions • Carefully blend to ensure homogenous mix • Hot compaction (120C) of Al/SiC powders acc. to weight fractions, under 7 ton pressure • Sintering in furnace for three hours (540C)

  19. Specimens • Pure aluminum • 10% SiC • 15% SiC • 20% SiC Specimens prepared for metallographic investigation

  20. Lab Report • Sketch the four microstructures • Identify any defects in the composite structure • Study the effect of the reinforcement on the mechanical properties in terms of their measured RHN, and calculated tensile strength

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