Material properties are intensive properties, which means they are independent of the amount of mass and may vary from place to place within the system at any moment. Materials science involves studying materials’ structure and relating them to their properties (mechanical, electrical, etc.). Once materials scientist knows about this structure-property correlation, they can then go on to study the relative performance of a material in a given application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and how it has been processed into its final form. Understanding material properties is essential for power plant personnel to understand why the material was selected for certain applications within their facility. Almost all processes that take place in nuclear facilities involve the use of specialized metals. A basic understanding of material properties is necessary for nuclear facility operators, maintenance personnel, and the technical staff to operate and maintain the facility and facility support systems safely.
Materials are frequently chosen for various applications because they have desirable combinations of mechanical characteristics. For structural applications, material properties are crucial, and engineers must consider them. The mechanical behavior of material reflects its response or deformation concerning an applied load or force. Key mechanical design properties are:
- Stiffness. Stiffness is the ability of an object to resist deformation in response to an applied force.
- Strength. Strength is the ability of a material to resist deformation.
- Hardness. Hardness is the ability to withstand surface indentation and scratching.
- Ductility. Ductility is the ability of a material to deform under tensile load (% elongation).
- Toughness. Toughness is the ability of a material to absorb energy (or withstand shock) and plastically deform without fracturing (or rupturing); a material’s resistance to fracture when stressed; a combination of strength and plasticity.
- Malleability. Malleability is the material’s ability to be flattened into thin sheets under applications of heavy compressive forces without cracking by hot or cold working means.
- Creep. Creep is the slow and gradual deformation of an object over time.