High-strength aluminum alloys

Frantsevych Institute for Problems of Materials Science, Ukrainian Academy of Sciences, 3 Krzhizhanovsky Str, 03680 Kiev-142, Ukraine 

Abstract The perspective directions of increasing mechanical properties of wrought and 

Key words high-strength aluminum alloys, dispersion hardening, quasicrystals, eutectic alloys, mechanical properties 

The pure aluminum is the very soft metal with hardness 210 MPa and yield stress 10 -h 15 MPa. But the modem methods of alloying made possible to increase hardness of A1 alloys to 2200 MPa, yield stress to 700 MPa and ultimate tensile stress to 800 MPa. High strength characteristics of these alloys are combined with plasticity to fracture 5 15 % that is enough for the practical use. 

This dramatic increase of strength has been possible due to very high plasticity of pure A1 (which has FCC structure) and due to fundamental and experimental investigations in the theory of alloying and physics of strength and plasticity. 

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Panels of high strength aluminum alloy (7075-T6) were used in this study. The panels were approximately 10 x 3 x 0.032 inch (25 x 7.5 x 0.08 cm) in size. The test environments for coating evaluation were (1) a 5% NaCl spray (fog) chamber according to ASTM Standard Method of Salt Spray (Fog) Testing (B117-73), and (2) a modified 5% NaCl/S02 spray (fog) chamber with SO gas introduced periodically - ASTM Standard Practice for Modified Salt Spray (Fog) Testing (G85-84(A4)). In the latter case, a constant spray of 5% NaCl was maintained in the chamber and SO2 was introduced for one hour four tines a day (every 6 hours)( ). Coated test panels were examined for corrosion after one- and two- eek exposure periods. 

Aluminum powder metallurgy continues to receive high research and development priority. A major objective is to produce final aluminum parts by direct pressing of rapidly solidified aluminum particles. The process handles high-strength aluminum alloy materials. 

Aluminum composites aim at combining high-strength aluminum alloys with alumina ceramic fibers and filaments to provide even higher-strength structural materials. 

Superplastic—high-strength aluminum alloys which can be plastically shaped into difficult designed parts used on cars and aircraft. 

Y. Xue et al Micromechanisms of multistage fatigue crack growth in a high-strength aluminum alloy. Acta Mater. 55, 1975-1984 (2007)... 

D.O. Sprowls and E.H. Spuhler, Greenletter, Alcoa, Avoiding SCC in High Strength Aluminum Alloy Structures, ASM International Corrosion, Vol. 13, Metals Park, OH, Jan. 1982. 

High-strength aluminum alloys are frequently deficient in resistance to corrosion. High-purity aluminum and certain aluminum alloys are considerably more resistant to corrosion but are deficient in strength. By applying surface layers of the corrosion-resistant metal to a core of the strong alloy a clad aluminum composite is achieved that has a corrosion unattainable by either constituent acting alone. 

POSTER TITLE Continous casting of high-strength aluminum alloys containing mininum 10% solute element... 

O N. Senkov, S. V. Senkova, andR. B. Bhat, High Strength Aluminum Alloys for Cryogenic Applications, in O. N. Senkov, S. O. Firstov, and D. B. Miracle, (Eds.), Metallic Materials with High Structural Efficiency, Kluwer Academic Publishers, Dordrecht, The Netherlands, 2004, p. This volume. 

HIGH STRENGTH ALUMINUM ALLOYS FOR CRYOGENIC APPLICATIONS... 

High strength aluminum alloys for cryogenic applications... 

Aluminum and alloys are not suitable for (1) alkalis, (2) acids at pH 4.5, and (3) mercury, which can be a significant risk in some liquified natural gas operations. The heat treatable, high-strength aluminum alloys of the 2000- and 7000-series are rarely used because of environmental cracking susceptibility. Aluminum and its alloys are susceptible to chloride pitting and to concentration cell problems such as crevice corrosion and under-deposit corrosion. 

Fig. 7.90 Effect of stressing direction on the intergranular stress-corrosion crack path in susceptible high-strength aluminum alloy. Dark boundaries are representative of ones favored for cracking for indicated direction of applied stress. Source Ref 97...

Fig. 7.112 Dependence of corrosion-crack-growth rate on stress intensity for two high-strength aluminum alloys in saturated NaCI solution at 23 °C. Crack orientation TL (stress in transverse direction crack propagation in longitudinal direction). Source Ref 159...

Fig. 7.114 Dependence of stress-corrosion-crack-growth rate on stress intensity for a high-strength aluminum alloy at various temperatures. Source Ref 1 59...

The SCC behavior of a high-strength aluminum alloy in several environments is shown in Fig. 7.113. The effect of cyclic stress-intensity range, AK, on the growth of fatigue cracks in the same high-strength aluminum alloy and in similar environments is shown in Fig. 7.125 (Ref 173). The similarity in the shapes of the two sets of curves should be... 

Fie. 7.125 Corrosion-fatigue-crack-growth rate as a function of stress-in-tensity range for a high-strength aluminum alloy in dry argon and indicated halide solutions. Source Ref 1 73... 

M.O. Speidel and M.V. Hyatt, Stress-Corrosion Cracking of High Strength Aluminum Alloys, Advances in Corrosion Science and Technology, M.G. Fontana and R.W. Staehle, Ed., Vol 2, Plenum Press, 1972, p 115-335... 

M.O. Speidel, Interaction of Dislocations with Precipitates in High Strength Aluminum Alloys and Susceptibility to Stress... 

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