Deformation
The change in dimensions and/or shape of a material or work-piece due to applied forces. Deformation can be elastic or permanent. Elastic deformation happens when the work-piece returns to is previous dimensions or shape when an applied load below the yield point is removed. Loads above the yield point cause permanent deformation when the change in shape or dimension is not reversed when the load is removed.
Related terms: Yield Point
Descaling
The removal of surface scale from hot worked or heat treated products by acid pickling or mechanical means such as grit or shot blasting. Caution is advised if stainless steels are mechanically descaled as blasting media can be embedded in the surface and act as corrosion initiation sites.
It can also refer to the removal of scale formed during hot working processes by the application of water, coal dust, brushwood, oil, etc.
Ductility
The ability of a metal or alloy to deform without cracking or failing under tensile loads. Materials with low ductility exhibit brittle behaviour and fail at more modest loads. Ductility typically decreases at lower temperatures and most materials will become brittle below a certain temperature called the Ductile-Brittle Transition.
Duplex Stainless Steels
Duplex stainless steels have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. The proportions are approximately 50% of each phase.
Duplex stainless steels:
•are stronger, by a factor of up to 2, than the austenitic and ferritic grades
•are tougher and more ductile than the ferritic grades
•have better stress corrosion resistance than the austenitic grades.
Related terms: Austenite, Austenitic Stainless Steel, Ferrite, Ferritic Stainless Steels