Mechanical and Corrosion Properties of Intermetallics Based on Aluminum

We study Al₃Sc, Al₃Zr, Al₃Hf, and Al₃V intermetallic compounds playing the role of hardening phase in aluminum alloys. We use the technology of rapid crystallization from the liquid state. We obtain relatively fine grains d ∼ 15 μm in size for cast materials. By the method of X-ray diffraction analysis, it is shown that the Al₃Zr intermetallic compound is a single-phase material, whereas the Al₃Sc, Al₃Hf, and Al₃V intermetallics consist of several phases. The investigation of the mechanical characteristics by the indentation method shows that the Al₃Hf intermetallic has the maximum hardness HV = 6.75 GPa and the maximum yield stress σ_SH = 4.86 GPa, whereas the Al₃Sc intermetallic has the minimum hardness HV = 2.0 GPa, the minimum yield strength σ_SH = 0.86 GPa and the most plastic phase δ_H = 0.88. It is established that, in a 3% NaCl solution, the corrosion potentials (E_corr) of the Al₃Sc, Al₃Hf, and Al₃V compounds have close values ((– 0.52)–(– 0.57) V). In the potential range close to E_corr, the dissolution rate of intermetallic phases in a 3% NaCl solution increases in the following order: Al₃Sc < Al₃Hf < Al₃V. The role of intermetallic phase in the process of corrosion dissolution of aluminum alloy depends on its chemical composition, which determines the value of E_corr in aggressive media. We prove that the anodic dissolution of an Al–3 wt.% Mg alloy doped with 0.3 wt.%. Sc in a 3% NaCl solution runs within the potential range more negative than the dissolution potential of the Al₃Sc intermetallic compound. Thus, the intermetallic phases are cathodic inclusions relative to the matrix of the Al–Mg alloy that do not selectively dissolve under the corrosion conditions.