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The current study investigates the influence of hot rolling on the microstructure evolution of the near-surface region on AA7050 aluminum alloy and the corrosion performance of the alloy. It is revealed that hot rolling resulted in grain refinement in the near-surface region, caused by dynamic recrystallization, and equiaxed grains less than 500 nm can be clearly observed. Fibrous grains were evident in the hot rolled AA7050 aluminum alloy with relatively lower rolling temperature or larger rolling reduction, caused by the more severe elemental segregation at grain boundaries, which inhibited the progression of dynamic recrystallization. The density of the precipitates in the fibrous grain layer was higher, compared with those in the equiaxed grain layer, due to the increased dislocation density, combined with more severe elemental segregation, which significantly promoted the nucleation of precipitates. With the co-influence exerted by low density of precipitates and dislocations on the improvement of the corrosion performance of the alloy, the rolled AA7050 alloy with decreased density of precipitates and dislocations exhibited better corrosion resistance. [ABSTRACT FROM AUTHOR]

The quenching sensitivity of an Al–Zn–Mg–Cu alloy containing trace amounts of Sc and Zr is studied by interrupted quenching experiments. Electrical conductivity of the quenched samples and the hardness of the samples subjected to one-stage and two-stage aging, are measured to construct the time–temperature–transformation (TTT) curves and the time–temperature–property (TTP) curves. It is revealed that the quenching sensitivity of the alloy is mainly influenced by the precipitation of coarse η phases during slow quenching, which preferentially nucleate and grow at grain boundaries and at the Al3(Sc, Zr) dispersoids that are incoherent with the matrix. The quenching sensitivity increases with the size and quantity of the coarse η phases. The nose temperature is 290 °C for both TTT and TTP curves, where the phase transformation rate is the fastest and the quenching sensitivity is the highest. Compared to one-stage aged samples, two-stage aged samples exhibit lower quench sensitivity due to the reduced transformation rate from η′ phases to η phases after slow quenching. The quenching sensitive temperatures range from 206 to 358 °C for the one-stage aged samples and from 213 to 352 °C for the two-stage aged samples. Moreover, based on the simulated TTT and continuous cooling transformation curves, an optimized quenching process is proposed in the present work. [ABSTRACT FROM AUTHOR]

The intergranular corrosion (IGC) resistance of the Al–Mg–Si alloy with low Zn addition treated by the interrupted aging treatment (T6I6) was investigated. The IGC results of the Al–Mg–Si alloy show that IGC resistance is enhanced by T6I6 aging treatment. The EIS results reveal that the T6I6-treated Al–Mg–Si alloy has lower double layer capacitance and higher charge transfer resistance than the T6-treated alloy. The superior IGC performance of the T6I6-treated alloy may be attributed to the finer and more densely distributed precipitates within the grains, smaller and discretely distributed precipitates along the grain boundaries and narrower precipitate-free zones (PFZs) compared to the T6-treated alloy. [ABSTRACT FROM AUTHOR]

In order to improve the corrosion and heat resistance of Al-Mg-Si alloy conductor materials, Ce, Sc, Y and Zr were added in Al-Mg-Si alloy to regulate the microstructure. The Al-Mg-Si-Ce-Sc-Y alloy was designed with excellent pitting and intergranular corrosion resistance by obtaining the micron-sized Fe-containing second phase with a lower potential difference to Al matrix, more dispersed grain boundary precipitates with a higher proportion of Si particles, narrower width of PFZ and ideal distribution of intergranular precipitates. The Al-Mg-Si-Ce-Sc-Y alloy also maintained higher hardness, strength and electrical conductivity after overaging and annealing and the corrosion/heat resistance mechanisms were proposed. • The corrosion and heat resistance of Al-Mg-Si alloy conductors were further enhanced. • The mechanisms of pitting and intergranular corrosion mechanisms in Al-Mg-Si alloys were proposed. • The microalloying of Ce，Sc and Y in Al-Mg-Si alloys with high electrical conductivity was established. [ABSTRACT FROM AUTHOR]

The intergranular corrosion and exfoliation corrosion behaviors of Al–Cu–Li–Zr–Sc alloys under different aging effects, such as single‐stage aging, strain aging, and double‐stage aging, were studied. Among the three aging treatments, single‐stage aging resulted in the best resistance to corrosion, followed by double‐stage aging; strain aging resulted in the worst corrosion resistance. A 3.5% precooling strain could increase the dislocation density, which promoted the precipitation of corrosion‐prone T1 phase and increased the corrosion driving force of the alloy. Double‐stage aging made the precipitated T1 phases finer and more uniform and reduced the number of equilibrium phases at grain boundaries, thus improving the corrosion properties of the alloy. The corrosion susceptibility of the alloy was attributed to the T1 phase and precipitate‐free zone (PFZ), and the underlying corrosion mechanism was revealed as preferential dissolution of the equilibrium phase at grain boundaries and its surrounding distortion zone, followed by expansion of the PFZ along the grain boundaries, resulting in the development of corrosion from the grain boundaries to the intragranular regions. [ABSTRACT FROM AUTHOR]

To characterize the hot deformation behavior of commonly used aluminum alloy, a homogeneous Al-Mg-Si-Mn-Cr alloy was analyzed by thermal simulation test at deformation temperature range of 653-803 K and strain rate range of 0.01-10 s−1. The flow stresses were predicted by modified Johnson-Cook model, modified Zerilli-Armstrong model and strain-compensated Arrhenius model. The results show that the three models are able to predict the flow behavior of the alloy. Strain-compensated Arrhenius model has the best simulation ability in predicting flow stresses, while the modified Johnson-Cook model has lower prediction accuracy and the modified Zerilli-Armstrong model has poorer predictive ability at low strain rates. Microstructure evolution shows that subgrain boundaries form at original grain boundaries at first, moving toward to the center of the deformed grains. The dislocation density decreases, while the number and the size of subgrains increase with the decreasing Zener-Hollomon (Z) parameter. Both dynamic recovery (DRV) and dynamic recrystallization take place in hot deformation process. DRV is considered to be the primary dynamic softening mechanism throughout the entire hot deformation range. Continuous dynamic recrystallization and discontinuous dynamic recrystallization operate concurrently at low strain rates and high temperatures. The relationship of subgrain size and predicted flow stress is presented. Moreover, activation volume is introduced to reveal the thermal activation mechanism during hot deformation. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of Al-Mg-Si alloy is studied based on diffusion mechanism. The quantity of low angle grain boundaries increases rapidly, accompanied by the formation of subgrains and recrystallization grains with the increase of strain. Dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX) are the main softening mechanisms, of which the DRV is dominant. The kinetics of dynamic recrystallization (DRX) represented by Avrami relationship shows that the DRX volume fraction increases with increasing strain. Physical-based diffusion constitutive model is established to demonstrate the flow behavior of the alloy. The relationship between diffusion activation energy and deformation condition is analyzed, and the dependence of creep exponent on temperature and strain is discussed. The result shows that the model describes the flow stress accurately. Lattice diffusion is the main diffusion mechanism during hot deformation. The variation of creep exponent can be reflected by dislocation density when the deformation mechanism is controlled by dislocation motion. Dynamic precipitation and the impediment of dislocation motion can lead to high value of creep exponent of the alloy. Unlabelled Image • Three types of physical-based diffusion models are established to demonstrate the flow behavior of the alloy. • The main diffusion mechanism during hot deformation is determined by constitutive analyses. • The relationships between creep exponent, diffusion activation energy and deformation condition are discussed. • The microstructure evolution and the dynamic softening mechanisms are investigated during hot deformation. [ABSTRACT FROM AUTHOR]