Damage Mechanisms and Anisotropy of an AA7010-T7452 Open-Die Forged Alloy: Fatigue Crack Propagation

Abstract

The process–microstructure–property relationship of high-strength 7000 series aluminum alloys during fatigue crack propagation (FCP) is highly relevant for safety during the design and service of aircraft structural components. It is scientifically evident that many metallurgical factors affect FCP properties, but partly contradictory or inconclusive results show that the quantitative description of the relationships is still a major challenge among researchers and engineers. Most research focuses on sheet or plate products and investigations lack quantitative information on the process–property relationship between open-die forged thick products and FCP. The present study contributes to this field by investigating the fatigue crack growth behavior of an open-die forged AA7010-T7452 aluminum alloy. Four different forging conditions comprising different characteristic microstructures are comparatively analyzed. The influence of grain size, grain shape, specimen orientation, crystallographic texture, and primary phase particles is investigated. Fractographic analysis reveals different active damage mechanisms during fatigue crack growth. Based on that, the microstructure features relevant to fatigue damage areidentified in each regime of crack growth.

Prediction of Fatigue Crack Initiation of 7075 Aluminum Alloy by Crystal Plasticity Simulation

“…The second issue is the crystallographic texture. It has been shown experimentally in aluminum alloys that the crystallographic texture has a significant effect on fatigue propagation and total fatigue life [ 25 , 26 ]. Virtual experiments based on numerical simulations also showed that the effect of the texture on fatigue crack initiation is not negligible [ 27 ].…”

Effect of Thermo-Mechanically Activated Precipitation on the Hot Deformation Behavior of High Strength Aluminum Alloy AA7075

“…However, it should be noted that both mechanisms, dynamic precipitation and dislocation multiplication, are simultaneously responsible for the obtained higher flow stress of the as-quenched condition. In the case of the TSM condition, the measured hardening rate θ in the later stages of deformation is higher, as is the noticeably increased particle size and, therefore, the large dislocation mean free path reduces the dislocation particle interactions significantly [39,45]. This phenomenon is explained by the fact that strain hardening is proportional to the ratio of the volume fraction to the size of particles or to the interparticle spacing.…”

A Review on Nonlocal Theories in Fatigue Assessment of Solids

“…Continuum damage mechanics [ 19 ] has been used to characterize fatigue crack initiation and propagation in general. It provides a macroscopic field variable that reflects the average microstructural material damage [ 20 , 21 ]. This so-called “damage variable” appears in the constitutive relations that regulate a material’s deformation behavior [ 22 ].…”