SEDL / STP / STP436-EB / STP32007S

Fractography and Microstructure of Aluminum Alloys 7075-T651 and 7075-T7351

Hunter, MS
Scientific associate, Alcoa Research Laboratories, New Kensington, Pa.

McMillan, JC
Group engineer, The Boeing Co., Renton, Wash.

Pages: 16    Published: Jan 1968

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Abstract

Specimens from 1⅜-in.-thick plate of 7075-T651 and 7075-T7351 alloys were examined by electron transmission, light microscopy, and electron fractography to relate microstructure, fracture topology, and mechanical and fracture properties. Material in the T7351 temper had a lower yield strength, smaller and more numerous fracture dimples, and an entirely transgranular fracture path. The T651 temper had a higher yield strength, fewer and larger dimples, and a partly intergranular fracture path. It was concluded that the beneficial effect of the lower yield strength more than offset the disadvantage of more numerous fracture dimple sites, and led to greater fracture toughness in the T7351 temper. The partially intergranular fracture was not significant in relation to fracture.