SYMPOSIA PAPER Published: 01 January 1978
STP28720S

Influence of Advanced Ingot Thermal-Mechanical Treatments on the Microstructure and Stress Corrosion Properties of Aluminum Alloy Forgings

Source

A new approach, the application of microstructure control to products possessing an optimized alloy chemistry, has been taken to develop an improved combination of properties in 7000 series wrought aluminum products. The technique developed is an ingot (intermediate) thermal-mechanical treatment (ITMT) process which optimizes the combination of static strength, fracture toughness, fatigue strength, and stress corrosion resistance of commercial aluminum alloy die forgings. Previously, high fracture toughness had been achieved in wrought products by sacrificing tensile strength or stress corrosion properties. The ITMT processes produce either a recrystallized grain structure by thermal treatments prior to working at lower-than-conventional (warm) working temperatures or an altered grain structure by hot working the previously recrystallized structure. In both cases, the resulting grain morphology is desirable for good fracture toughness. Results of testing forging material show that ITMT on a high purity 7475 alloy produces advantageous fatigue crack propagation rates in 3.5 percent salt solution in comparison to 7075-T73, and stress corrosion resistance equivalent to 7075-T73 in addition to attractive tensile properties and high fracture toughness.

Author Information

Zola, J
Boeing Vertol Company, Philadelphia, Pa
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Details
Developed by Committee: E08
Pages: 169–188
DOI: 10.1520/STP28720S
ISBN-EB: 978-0-8031-4714-0
ISBN-13: 978-0-8031-0314-6