Journal of Materials Science, Vol.35, No.4, 907-915, 2000
Characterization of a delta/gamma duplex stainless steel
A duplex stainless steel was investigated in both as-received sheet and after annealing at temperatures ranging from 850 to 1100 degrees C. The sheet presents a deformation texture in both phases, austenite and ferrite, induced by cold rolling. Microstructure in the as-received material consists of island-like austenitic grains in a ferrite matrix. These austenitic grains are elongated with an average size of 6, 20 and 40 mu m along the normal (ND), transversal (TD) and rolling direction (RD). Quantitative texture measurements demonstrated that texture components are distributed mainly along the theta-fiber (ND parallel to [100]) and alpha-fiber (RD parallel to [110]) for the ferrite and the zeta-fiber (ND parallel to [110]) for the austenite. After recrystallization, a decrease in the intensity of the mean fibers and an increase in the minor components was observed in both, ferrite and austenite. Therefore, a similar texture was reached in both phases after annealing at 1050 degrees C. Microstructural characterization after annealing at temperatures above 850 degrees C showed that the elongated austenitic grains transform in colonies of equiaxic grains of about 10-15 mu m in size. These colonies are surrounded by a ferritic matrix at annealing temperatures above 1000 degrees C or by a laminar microstructure at temperatures below 950 degrees C. This laminar microstructure includes sigma phase and austenite formed from delta ferrite, and untransformed delta ferrite.