Superplasticity of (α+γ) duplex stainless steel with elongated secondary phase

Effect of initial (α+γ) microstructure on the superplasticity of a hot forged Fe-26Cr-8Ni (α+γ) duplex stainless steel with elongated secondary γ precipitates was examined. The hot forged specimens contain the (α+γ) duplex structure with γ phase elongated along the longitudinal direction of the forged bar. Heavy cold rolling of hot forged specimens promotes recrystallization of γ and a during heating to and holding at 1273K (tensile deformation temperature), resulting in the formation of finer, more equiaxed (α+γ) microduplex structures. The specimens heavily cold rolled after forging exhibit large superplastic elongation nearly the same as the (α+γ) microduplex specimen produced by a conventional thermomechanical processing (solution treatment + heavy cold rolling + aging) although hot forged specimens show much smaller elongation.