Abstract
Microstructure of Al-Cu-Yb and Al-Cu-Gd alloys at casting, hot-rolled -cold-rolled and annealed state were observed; the effect of annealing on the microstructure was studied, as were the mechanical properties and forming properties of the alloys, and the mechanism of action was explored. Analysis of the solidification process showed that the primary Al solidification is followed by the eutectic reaction. The second Al8Cu4Yb and Al8Cu4Gd phases play an important role as recrystallization inhibitor. The Al3Yb or (Al, Cu)17Yb2 phase inclusions are present in the Al-Cu-Yb alloy at the boundary between the eutectic and aluminum dendrites. The recrystallization starting temperature of the alloys is in the range of 250–350 °C after rolling with previous quenching at 590 and 605 °C for Al-Cu-Yb and Al-Cu-Gd, respectively. The hardness and tensile properties of Al-Cu-Yb and Al-Cu-Gd as-rolled alloys are reduced by increasing the annealing temperature and time. The as-rolled alloys have high mechanical properties: YS = 303 MPa, UTS = 327 MPa and El. = 3.2% for Al-Cu-Yb alloy, while YS = 290 MPa, UTS = 315 MPa and El. = 2.1% for Al-Cu-Gd alloy.
Highlights
Mining, Metallurgy and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Abstract: Microstructure of Al-Cu-Yb and Al-Cu-Gd alloys at casting, hot-rolled -cold-rolled and annealed state were observed; the effect of annealing on the microstructure was studied, as were the mechanical properties and forming properties of the alloys, and the mechanism of action was explored
The results showed that the hardness of Al-Cu-Yb and Al-Cu-Gd alloys decreased with increasing annealing temperature and time, this may be attributed to the decrease in dislocation density, and formation of subgrains
The results showed that the hardness of Al-Cu-Yb and Al-Cu-Gd alloys decreased with increasing annealing temMetals 2021, 11, x FOR PEER REVIEW
Summary
Metallurgy and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Abstract: Microstructure of Al-Cu-Yb and Al-Cu-Gd alloys at casting, hot-rolled -cold-rolled and annealed state were observed; the effect of annealing on the microstructure was studied, as were the mechanical properties and forming properties of the alloys, and the mechanism of action was explored. Al-Cu alloy is an important series of aluminum alloys, because of its excellent properties, such as high specific strength, etc. High strength and excellent machinability, Al-Cu alloys are important candidates for steel substitution in some applications in the aerospace and automotive industries [8]. Rare earth elements have been added in aluminum alloys to improve the tensile strength, heat resistance and corrosion resistance [11,12]. When Sc was added into Al alloys, a thermo-stable L12 -type (AuCu3 ) Al3 Sc phase would form in the Al solid solution, which was able to inhibit the re-crystallization and the grain growth and significantly improve the high temperature properties of the alloys [13,14]. It was found that after partial replacement of Sc with either Yb or Gd, the mechanical properties, such as incubation time and peak hardness of the Al alloy were improved [16]
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