<prompt> Duplex steel is made up of:Martensitic steel and austenitic steelFerritic grain of stainless steelFerritic austenitic grains of stainless steelFerritic martensitic grains of stainless steel  <response>: Duplex stainless steel is a combination of both ferritic and austenitic grains of stainless steel. The basic chemical composition of duplex stainless steel is an equal mix of ferrite and austenite. This combination creates some very beneficial properties for this family of stainless steels. 