Estudo da tenacidade e fadiga em meio assistido da liga de Al-Li de grau aeronáutico AA2050-T84

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

“…In both case the values of da/dN was found to be approximately 1E-5 mm/cycle for a ΔK = 6 MPa.m 1/2 . As was observed by Maciel 15 , the effect of crack closure on the FCG rate in this region was quite intense in this alloy in presence of the saline fog. It is assumed that it may have persisted at the beginning of the Paris-Erdogan regime, neutralizing the environment effect (salt fog effect), i. e., causing reduction in the FCG rate by wedging effect.…”

“…In this study, in the saline environment, the value of ΔK th was only evaluated for the new AA2050-T84 (Al-Cu-Li) and it was observed that this value increased to ΔK th = 4.9 MPa.m 1/2 . However, from the results from Maciel 15 , it was observed that the effective value of the stress intensity range, ΔK thef = 3.0 MPa.m 1/2 is quite similar to the one in air.…”

“…A special acrylic cell and a reservoir for fog generation were specially fabricated, see Figure 2. In this setup, the fog circulated through the cell, supplied by the external reservoir and then expelled to the external environment, detail may be found elsewhere 15 . Crack length was measured using elastic compliance technique as recommended by the ASTM E647-11 14 , with the clip gage mounted at notch mouth, providing the crack-mouth-opening displacement (CMOD).…”

Estudo de fadiga e tenacidade de ligas de alumínio e alumínio-lítio soldadas por fricção-mistura (FSW) submetidas a atmosferas corrosivas e criogênicas

“…A liga ternária de Al-Cu-Li 2050 possui densidade de 2,71 g∕cm³ e passou pelo tratamento térmico T84 que segundo Kaufman [18], é obtido pelas etapas de solubilização com temperatura entre 480⁰C a 540⁰C, encruamento com laminação a frio, alívio de tensões e envelhecimento natural. A Figura 2.5, mostra a microestrutura bandeada, típica do processo de laminação, com forte texturização na direção L e em menor escala na direção T. Segundo Maciel [19] e Bonazzi [20], este material apresenta possível presença de precipitados responsáveis pelo aumento da resisência mecânica como S'(Al2CuMg), 1 (Al2CuLi), θ' (Al2Cu) e a formação de pequenas partículas de 6 . Sua composição química, de acordo com a norma AMS 4413 [21]…”

“…Reagente Keller. Aumento 50x [19]. Composição química da liga de alumínio aeronáutica de alta resistência 2050-T84.…”