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Materials/Processes

Selection of Materials
Specific Metals
  Metal Ores
  Iron and Steel
  Decarburization
  Aluminum/Aluminum Alloys
  Nickel and Nickel Alloys
  Titanium and Titanium Alloys


General Manufacturing Processes

Metallic Components
Ceramic and Glass Components
Polymers/Plastic Components
Composites

Manufacturing Defects
Metals
Polymers
Composites

Service Induced Damage
Metals
Polymers
Composites
Material Specifications

Component Design, Performance and NDE
Strength
Durability
Fracture Mechanics
Nondestructive Evaluation

Bulk Defects

Bulk defects occur on a much bigger scale than the rest of the crystal defects discussed in this section. However, for the sake of completeness and since they do affect the movement of dislocations, a few of the more common bulk defects will be mentioned. Voids are regions where there are a large number of atoms missing from the lattice. The image to the right is a void in a piece of metal The image was acquired using a Scanning Electron Microscope (SEM). Voids can occur for a number of reasons. When voids occur due to air bubbles becoming trapped when a material solidifies, it is commonly called porosity. When a void occurs due to the shrinkage of a material as it solidifies, it is called cavitation.

Another type of bulk defect occurs when impurity atoms cluster together to form small regions of a different phase. The term ‘phase’ refers to that region of space occupied by a physically homogeneous material. These regions are often called precipitates. Phases and precipitates will be discussed in more detail latter.