ASTM A790 S31803/S32205 Duplex Stainless Steel Pipe Duplex stainless steels are extremely corrosion resistant, work hardenable alloys. Their microstructures consist of a mixture of austenite and ferrite phases. As a result, duplex stainless steel display properties characteristic of both austenitic and ferritic stainless steel. This combination of properties can mean some compromise when compared with pure austenitic and pure ferritic grades. Duplex stainless steels are in most cases, tougher than ferritic stainless steel Strengths of duplex stainless steel can in some cases be double that for austenitic stainless steel.