Texture and microstructure of annealed AISI302 steels wires

The texture and microstructure of cold-drawn and annealed wires made from AISI 302 austenitic steel were the object of the investigations. The wires were deformed up to 70.6% and 91.6% of reduction and annealed for I hour in the temperature range 550 - 850 degrees C. Significant amount of martensite, formed due to the strain induced (gamma ->alpha' a') transformation, were detected within the deformed structure by applying magnetic and X-ray diffraction methods. During annealing of deformed wires the ;reverse (alpha'->gamma) transformation of martensite into austenite occurred. The texture analysis of the examined wires was conducted on the basis of experimental pole figures as well as calculated inverse pole figures and orientation distribution functions. The austenite texture in cold-drawn wires was described as a strong axial texture with two < 111 > and < 100 > components. The martensite texture contained two components, the major was the < 210 > and the weaker one the < 110 > orientation. The rnicrostructure of the deformed wire exhibited a fibre character. The structure of martensite was fine and dispersed appearing mainly within the areas of the austenite matrix displaying strain localization. In the austenite texture after annealing the same two < 111 > and < 100 > orientations remained dominant. The martensite texture weakened with increasing annealing temperature, due to the reverse transformation (alpha'->gamma). Effects of deformation were still observed in the case of the wires annealed at lower temperatures (below 650 degrees C). TEM investigations confirmed the presence of ultra fine martensite in the microstructure. When annealed at higher temperatures (above 650 degrees C), the fibre rnicrostructure was retained, but with clearly visible effects of the recovery and recrystallisation processes and the martensite was not observed any more.