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SEM，EBSD and TEM techniques were used to study the effects of grain boundary precipitation characteristics and the Fe-containing second phase（Al7Cu2Fe phase） formed under different aging regimes on the intergranular corrosion properties of Al-Zn-Mg-Cu alloys. The results show that the change rate of Fe content of Al7Cu2Fe phase with large surface size of aluminum alloy specimen after aging at 120 ℃ for 24 h is the largest，while the phase change rates of Fe content of Al7Cu2Fe phase with small size in specimens aging at 120 ℃ for 60 h and 120 h are greater. With the increase of aging time，the corrosion time of surface pitting caused by Al7Cu2Fe phase in 7050 aluminum alloy specimen is shortened，and the depth of intergranular corrosion decreases，indicating that its intergranular corrosion resistance is enhanced with the increase of aging time. In addition，with the increase of aging time，the PFZ （precipitation-free zone） width of the sample increases，the number of nuclei of GBPs（grain boundary precipitation） decreases，the spacing between GBPs increases，and the grain orientation prone to intergranular corrosion is gradually concentrated.

The time-temperature-transformation (TTT) diagrams of 7A36 aluminum alloy extruded plate were determined by an interrupted-quench method. The quenching precipitation behavior was investigated by calculate phase diagram(CALPHAD) combined with optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), scanning transmission electron microscopy(STEM) and high-resolution transmission electron microscopy(HRTEM). The results show that the critical quenching rate for inhibiting the phase transition of 7A36 aluminum alloy by 0.5% is about 15.7 ℃/s. Based on 10%TTT diagram, the nose temperature is determined to be about 338 ℃ with the transformation time of about 22 s. The precipitation of η(MgZn2), T(Al2Zn3Mg3), S(Al2CuMg) or Cu-Zn rich Y phases can be found depending on different isothermal holding temperatures and time, and the precipitation behavior is described in the TTT curve, which is described as a time-temperature-precipitation diagram.η equilibrium phase tends to occur at grain boundary(GB) first and then at sub-grain boundary(SGB) and on dispersoids in the interior of grains, at higher isothermal holding temperature, the size of η phase is larger. The electrical conductivity increases first and then decreases with the increase of holding temperature; isothermal holding at 420 ℃, the increase of electrical conductivity is caused by precipitation of η phase and T phase, while at 330 ℃ and 240 ℃, the increase of electrical conductivity is due to the precipitation of η phase, T phase, S phase and Y phase.

Precipitation temperature of Al3(Sc, Zr) dispersed phase in Al-Cu-Li-Sc-Zr alloys was investigated by DSC. Four kinds of triple-step homogenization treatments were designed to obtain the holding temperature and time of Al3(Sc, Zr) dispersed phase particles. After hot rolling, solution treatment and aging treatment, the mechanical properties of homogenized samples were compared by room temperature tensile tests. The apparent activation energy was calculated by the results of aging hardening curves, the morphology and composition of the second phase in homogenized samples were investigated by SEM and EDS, and the grain orientation characteristics of samples after solution treatments were investigated by EBSD. The results show that the Al3(Sc, Zr) dispersed phase at 460 ℃ which is the second step temperature in homogenizations is more favorable than that at 410 ℃ during the multistage homogenization treatments, which can control grain structure, inhibit recrystallization and promote the precipitation of strengthening phase containing Li during aging treatment. The compound action of grain boundary strengthening, texture composition and precipitated phase improves the mechanical properties of the alloys. In addition, for the dispersed particles like Al3(Sc, Zr) separated, many sub-grain microstructures are conserved after hot deformation annealing, which makes alloys deform uniformly during tensile process at room temperature and improves the ductility of the alloys.

In the present work, after annealing at 150 °C–450 °C for 1 h, the influence of precipitate, grain structure and texture evolution on the discharge properties of the Al–0.25Mg–0.2Sn–0.04Ga–0.04In anode for Al–air batteries was investigated in detail. When the annealing temperature is not higher than 250 °C, the alloy shows high electrochemical activity attributed to the fine fibrous structure with high-density of dislocations and high corrosion resistance due to the high fraction of low angle grain boundaries, brass and Goss textures. The 150 °C annealed alloy exhibits high specific capacity, energy density and anode utilization of 2722.3 mA h g−1, 3020.0 mW h g−1 and 91.35%, respectively at 60 mA cm−2. The alloy annealed at 350 °C displays the lowest discharge performance as a result of the growth of grains, high fraction of high angle grain boundaries with Sn-rich phases and the reduction of brass and Goss textures. When the annealing temperature further increases to 450 °C, both the corrosion resistance and discharge voltage at a high current density of the alloy improve on account of the dissolution of Sn-rich phases. This is responsible for the highest discharge capacity of 2777.8 mA h g−1 and anode efficiency of 93.21% of the alloy at 60 mA cm−2. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, mechanical, and tribological properties of (Ti42V28Zr15Nb15)100-xAlx lightweight refractory high-entropy alloys (LRHEAs) were systematically investigated. The results show that the single BCC solid solution structure of LHEAs is maintained after the addition of Al elements, and no other phases are formed. The addition of Al elements to the alloys can be reduce density, improve properties, and enhance wear resistance. While the hardness of the alloy increased from about ~ 352 HV to ~ 430 HV, the tensile ductility decreased significantly. The main reason for the increase in hardness is the strong bonding between aluminum atoms and other atoms. On the other hand, the severe impairment of the tensile properties may be due to the decrease in GNDs. Although the addition of Al helps to reduce the coefficient of friction, the wear rate of the alloy increases. [ABSTRACT FROM AUTHOR]