Recrystallization Behavior of IF Steel at the Interface of Aluminum Junction

Abstract

Two cold-rolled IF steel sheets sandwiching an aluminum sheet were heat-treated at 650°C, and the recrystallization behavior in the interfacial region between the IF steel and pure aluminum was observed and analyzed. The tongue-like structure of the η-Fe₂Al₅ phase appeared in the reaction zone and the recrystallized structure of the IF steel was characterized by an equiaxed structure including subgrains in the region surrounded by the η phase. In contrast, a bcc-ferrite phase elongated with a pancake shape was mainly observed in the other regions. The η phase grew preferentially along the c-axis, and the growing η phase caused distortion of the surrounding iron due to the difference in the molar volume. This suggests that compressive strain is generated along both a-axis and b-axis, and tensile strain is generated along c-axis of the η phase. The growth of the η phase obviously changed the recrystallization behavior of the IF steel. The development of the γ-fiber crystalline texture (<111>/ND), a typical recrystallization texture of IF steel, was not observed in the region surrounded by the tongue-like η phase. The local misorientation in the vicinity of the two-phase interface could not explain the texture change. It is suggested that the growth of the tongue-like η phase caused constraint of the surrounding region and affected nucleation in the recrystallization of the ferrite.