Aging phenomenon in low molybdenum Fe-21Cr-5Mn-1.5Ni alloy: Microstructure evolution, texture development and corrosion behavior

In the present work, the effect of long-term aging at 750 degrees C up to 480 h on microstructure evolution, texture development and corrosion behavior of a low molybdenum Fe-21Cr-1.5Ni-5Mn alloy has been investigated systematically. An increase in aging time results in increase in proportion of sigma-phase. The sigma-phase formation took place by the eutectoid decomposition reaction: 8 -* sigma + gamma 2. The sigma-phase did not show any specific orientation relationship with neighboring 8 ferrite grains. The initial solution annealed sample showed the presence of strong Brass ({110}<112>), Cube ({100}<001>), Goss ({110}<112>), and minor Cu (<{112}111>) in austenite, and strong gamma-fiber (normal direction, ND//<111>) along with minor alpha-fiber (rolling direction, RD//<110>) in ferrite. After, long-term aging up to 480 h, austenite showed strong Cu ({112}<111>) and minor Brass ({110}< 112>) along with Cube ({100}<001>). Ferrite, on the other hand, showed gamma-fiber. The lower amount of Cr/Mo and higher N in Fe-21Cr-1.5Ni-5Mn alloy was not enough to avoid the sigma precipitation, however, it delayed its precipitation. The increase in sigma-phase with aging time resulted in a decrease in corrosion resistance.

Automated summary

This study systematically investigated the effect of long-term aging at 750 degrees C on the microstructure evolution, texture development, and corrosion behavior of a low molybdenum Fe-21Cr-1.5Ni-5Mn alloy. The results showed that an increase in aging time resulted in an increase in the proportion of sigma-phase. The sigma-phase formation did not have a specific orientation relationship with neighboring ferrite grains. The lower amount of Cr/Mo and higher N in the alloy delayed the precipitation of the sigma-phase but did not prevent it. The increase in sigma-phase with aging time led to a decrease in corrosion resistance.