Effects of microstructure on the fatigue crack growth behavior of light metals and design considerations

Anastasios G Gavras,Brendan F Chenelle,Diana A Lados

doi:10.1590/s1517-70762010000200033

Anastasios G Gavras, Brendan F Chenelle + Show 1 more

Open Access

https://doi.org/10.1590/s1517-70762010000200033

Copy DOI

Abstract

Fatigue crack growth mechanisms of long and small cracks were investigated in cast and wrought aluminum and titanium alloys with various microstructures (as-cast A535, 6061-T61, and mill-and beta annealed Ti-6Al-4V). In addition, friction stir welded and cold spray processed 6061-T61 were also investigated. The effects of microstructure on the fatigue crack growth response of each material were evaluated. Long crack growth data were generated on compact tension specimens at low and high stress ratios R=0.1 and 0.7, respectively. Small crack growth testing was performed on corner and surface flaw tension specimens at low stress ratio, R=0.1. Fatigue crack growth mechanisms at the microstructural scale of the materials were identified and will be discussed. Closure corrections were applied to long crack growth data, and the results were compared to experimental small crack growth data. Models for small crack growth predictions from long crack growth data will also be presented and discussed.

Highlights

Fatigue crack growth behavior is a crucial factor for the design and performance of modern structural materials
Limited studies have been done on the fatigue crack growth behavior of Al-Mg alloys
Low residual stresses were ensured through increasing material removal after processing to focus on the effect of the microstructure on fatigue crack growth behavior

Summary

Introduction

Fatigue crack growth behavior is a crucial factor for the design and performance of modern structural materials. It has been shown in the past that the presence of residual stresses, introduced during processing, dictates the fatigue performance [1,2,3,4]. In the absence of residual stresses, fatigue crack propagation depends on the material’s microstructural features. Limited studies have been done on the fatigue crack growth behavior of Al-Mg alloys. Roughnessinduced closure mechanisms have been proposed to explain the lower threshold and higher fatigue crack growth rates of ultrafine grained Al-Mg alloys versus conventional larger grain sized alloys [5]. Similar grain size effects on the fatigue crack growth response have been observed [6]

Methods

Results

Conclusion