Selection of an appropriate material for a particular purpose requires a careful consideration of the conditions to which the material will be subject.
Some of the more common conditions that the engineers must consider are the mechanical behaviour of the material, the stresses that will be applied to the material, the surrounding temperature and environment, and the cost and production of the material.
Forming or processing can introduce a number of flaws or defects into the material structure that can act as stress concentrators. Components must be designed to compensate for these flaws or they must otherwise be identified and either removed or corrected. Common processing flaws include shrinkage, porosity, residual stresses, inclusions, segregation, and sensitisation at grain boundaries.