Tension Characteristics of Notched Specimens for Al-Li-Cu-Zr Alloy Sheets with Various Cerium Contents

摘要

In the present article, the high strength Al-Li-Cu-Zr alloy sheets modified by a rare earth element, Ce, are considered for possible application in practical aircraft products containing structural notches or stress concentrations; accordingly, a study has been made on the effects of stress concentration levels and Ce contents on the tension strength of notched specimens for the alloy sheets. Moreover, a discussion has been set off on the theoretical predictability on the basis of a theoretical expression for the notch strength by means of the mechanical properties of the smooth specimens. The test results show that when the stress concentration level increases, the notch strength linearly decreases in the double logarithmic coordinate; by comparison with the Ce-free alloy, the Ce-containing alloy sheets exhibit an insignificantly varying notch strength when the Ce content changes from 0.13 to 0.31 wt pct in the transverse orientation specimens or is 0.21 wt pct in the longitudinal orientation specimens even though their ductility for the smooth specimens can be improved to a certain degree by the Ce modification. The test data of notched specimens under the theoretical stress concentration factor (K_t) from 2.0 to 8.0 agree better with the predicted values of notch strength. Therefore, in accordance with some engineering properties such as the ultimate tensile strength (UTS), percentage elongation (EL), and Young's modulus (E) of the smooth specimens, the notch strength of the alloy sheets under plane strain state can be easily estimated in a certain range of stress concentration levels.