EFFECT OF SINGLE AND DUPLEX AGING ON MICROSTRUCTURE AND FATIGUE CRACK GROWTH IN Al-Li-Cu ALLOY AF/C-458

摘要

Microstructure and fatigue crack growth (FCG) rates in Al-Li-Cu alloy AF/C-458 were studied following single and duplex aging treatments on specimens that were given a 6 percent stretch after solution heat treatment. Aging response was determined using hardness and compression yield strength measurements. Quantitative transmission electron microscopy methods were used to characterize average size, volume fraction, number density, and interparticle spacing of strengthening precipitates, δ'(Al_3Li) and T_1 (Al_2CuLi). Strength and fatigue crack growth rates for select heat treatments were obtained and were related to the precipitate microstructure and compression strength data. The relationship between precipitate characteristics and mechanical properties are discussed.