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 Arconic-patented-T77 aging process.
Arconic 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, Arconic 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.
Applications In Service
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.