Aluminum alloy 7150-T77 provides an unsurpassed combination of high strength and corrosion resistance compared to other 7XXX series aerospace alloys of similar strength. Alloy 7150-T77 provides peak strength through the patented-T77 aging process.
Corrosion Resistance
Alcoa guarantees an accelerated test exfoliation rating of EB or better for 7150-T7751 plate and 7150-T77511 extrusions, based on the 48-hour ASTM G34 EXCO test. This performance level is equivalent to other 7XXX-series alloys in an “exfoliation resistant” -T76 condition.
The accompanying photographs display the results of long-term, aggressive seacoast atmospheric exposure. T/2 plane specimens of 7150-T7751 plate display a typical behavior of “P” (pitting and no exfoliation) after a 2 year, 11 month exposure. For comparison, T/2 plane specimens of similarstrength 7150-T6 plates are rated ED (severe exfoliation) after exposure of 2 years and 6 months. This severe corrosion condition is not considered unusual for 7XXX-T6 alloys exposed at seacoast for this duration.
Aluminum alloy 7150-T77 also provides good stress corrosion cracking resistance. When specified, Alcoa will certify that 7150-T7751 plate and 7150-T77511 extrusions pass the 20-day alternate immersion test per ASTM-G47 at 25 ksi (172 MPa) short transverse applied stress. Other guarantees are subject to inquiry.
Typical Applications: Stiffened upper wing panels and lower horizontal stabilizer panels of Alloy 7150-T7751 plate and 7150-T77511 extrusions are now in service on numerous civil and military transport aircraft. The alloy and temper are effective in compression-loaded stiffened panels requiring a combination of high compressive yield strength, moderately high toughness, good fatigue and corrosion resistance vs. stiffened panels made from earlier products such as 7150-T6 or 7075-T6. Other successful applications of 7150-T77 include: extruded fuselage stringers, fuselage keel beams, and airline passenger seal tracks.
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