Effect of inhomogeneous microstructure evolution on the mechanical properties and corrosion behavior of rotary friction welded AA2024 joints

The intrinsic flaws of radial gradient heat generation and uneven deformation during rotary friction welding process will damage the structural integrity of the resultant joint but almost no attention has been paid before. The relationship between radial inhomogeneous microstructure, mechanical properties and corrosion behavior of rotary friction welded 2024 aluminum alloy joint was thus systematically investigated to reveal the impact. The results showed that the highest and lowest tensile strength appeared in 0.25R and 0.75R positions along radius, respectively. And the texture evolution in 0.25R and 0.75R positions can be summarized as: Copper {112)< 111 > -> S{123} < 634 > -> Brass {011)< 211 > (strong) -> Brass {011}< 211 > (weak), Copper {112} < 111 > -> S{123) < 634 > -> Rotated Goss {110) < 110 > -> Brass {011} < 211 > (weak), respectively. The corrosion resistance of rotary friction welded joint is gradually weakened along radius, caused by the different distribution of grain size, second phase particles and residual stress. The heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ) adjacent to HAZ and dynamic recrystallization zone (DRZ) exhibited high corrosion susceptibility and occurred severe exfoliation corrosion. But the TMAZ adjacent to DRZ and base metal acquired the good corrosion resistance due to the dispersive distribution of GPB zones. Furthermore, the qualitative relationship between microhardness and corrosion susceptibility was revealed. The regions with low microhardness exhibited high corrosion susceptibility while the regions with high microhardness (except DRZ) presented good corrosion resistance.