A Study of Constituent, Dispersoid, and Hardening Particles in the Fracture of 7075 Aluminum Alloys.
Abstract
Ten different alloys based on the 7075 composition are used to study the effect of purity level, dispersoid type, and heat treatment on 7075's fracture toughness. Five different purity levels ranging from 0.30 w/o to 0.30 w/o Fe+Si and two different dispersoid types were investigated. Each alloy was given two different heat treatments with both the longitudinal and the long-transverse directions tested. The notched round tensile test was modified to give the 'plastic energy per unit area'. This parameter used for ranking fracture toughness gave the same results as the total energy per unit area measured on precracked Charpy specimens. Moreover, the fracture toughness ranking for these ten alloys was the same in the longitudinal and long-transverse directions. This suggests the elongated distribution of constituent particles in the rolling direction does not change the failure mechanism. Fractographic evidence showed a clear difference in the fracture topography between the ten alloys. An analysis of variance demonstrated that heat treatment was the most significant variable investigated that affects fracture toughness. This result supports a two-stage ductile fracture failure mechanism which suggests that the dispersoid and hardening particles are primarily responsible for the fracture toughness of the higher purity aluminum alloys used by the aerospace industry today. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1977
- Accession Number
- ADA041421
Entities
People
- Joseph S. Santner
Organizations
- Air Force Research Laboratory