Study of the Effects of Two-Step Ageing Heat Treatment on Fatigue Crack Growth on an AA7050 Aluminum Alloy

Abstract:

Aluminum alloys are the first chosen materials for aircraft structures since 1930 due to their high ratio between properties and density. Currently, aircraft industries use Al-Zn-Mg-Cu alloys, with T7451 temper, which it shows high strength, fatigue and corrosion resistance. The improvements properties are result from the η’ phase formation, MgZn₂. The aim the present work is to propose an alternative route for ageing heat treatment at one AA7050 aluminum alloy, the manner which the formation of η’ phase particles at lower temperatures and longer periods of treatment is obtained. According to the literature, ageing treatments at low temperatures and longer periods optimize the usage of the solution atoms, favoring the growth and nucleation particles. As a result, there is an increase in the density of the particle improving the alloy properties. These improvements show a decrease up to 13% in the crack propagation rate for moderate ΔK levels, keeping the same levels of Vickers hardness but with decay of 12% of ultimate tensile strength.

• Periodical: Advanced Materials Research (Volumes 891-892)
• Pages: 1111-1116
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.891-892.1111
• Online since: March 2014
• Authors: Luis Otavio Ribas Lima, Sheila Cristina Jacumasso, Cassius Olivio Figueiredo Terra Ruchert, Juliana Paula Martins, André Luis Moreira Carvalho*
• Keywords: AA7050 Aluminum Alloy, Ageing Heat Treatment, Fatigue Crack Growth (FCG), T6, T614-65, T7451

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