Environmentally-assisted Fatigue Crack Growth in AA7050-T73511 Al Alloy and AA2050-T84 Al-Cu-Li Alloy

• Autor(a) principal: Moreto,Jéferson Aparecido
• Data de Publicação: 2015
• Outros Autores: Paschoal Júnior,Fernando Antônio, Maciel,Carla Isabel Santos, Bonazzi,Luis Henrique Camargo, Leonelli Júnior,José Francisco, Ruchert,Cassius Olívio Figueiredo Terra, Bose Filho,Waldek Wladimir
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Materials research (São Carlos. Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392015000601291
• topic: Al-Li alloys; low temperature; corrosion-fatigue; seawater fog

The aim of this study was to evaluate and compare the effect of low temperature and saline environment on the fatigue crack growth behavior of the AA7050-T7451 Al alloy and the recently developed AA2050-T Al-Cu-Li alloy. Fatigue at room and low temperature and corrosion-fatigue tests were carried out using an applied stress ratio (R) of 0.1, 15 Hz frequency (air at RT and –54 °C) and 1 Hz frequency (seawater fog) using a sinusoidal wave form. In the near-threshold region, in air and at RT it was found a ΔKth = 2.9 MPa.m1/2 for AA2050-T84, in saline environment this value increased to ΔKth = 4.9 MPa.m1/2, due to closure effect through wedge effect by the corrosion products. At the beginning of the Paris-Erdogan region, the crack closure effect was not present for the AA7050-T7451, but persisted for the AA2050 Al-li alloy. It was observed that both alloys were equally affected by temperature reduction. When the saline environment is considered it was observed that the AA7050-T7451 presents lower m value (2.6) than the one for AA2050-T84 (3.4), meaning a lower FCG rate variation with ΔK, however it presented the highest C value, as a consequence the worst FCG behavior.