Effect of Double Aging on the Toughness and Precipitation Behavior of a Novel Aluminum-Lithium Alloy

摘要

Precipitation behavior and mechanical properties of a novel aluminum-lithium alloy were investigated during a double-aging treatment to obtain superior combination of strength and plasticity. The double-aging process, involving subsequent high to low temperature treatments, was applied to strengthen the alloy. Transmission electron microscopy was used to characterize the precipitation behavior of the alloy, while tensile and tear tests were performed to evaluate the mechanical properties. The results indicated that the samples double aged at (165 A degrees C, 10 h) + (140 A degrees C, 35 h) possessed a desired combination of strength, plasticity, and toughness. T (1) phases were observed to nucleate preferentially at the defects during the first (primary) aging step. During the second (secondary) step of aging, these phases grew further and promoted the formation of new precipitates. Compared to the single-aging treatment, the double-aging treatment effectively prevents coarsening of T (1), which is beneficial in improving the plasticity and toughness of the alloy.