Effect of Yttrium on Cryogenic Mechanical Properties and Fracture Behavior of Al-Li-Cu-Mg-Zr Alloy
The effect of various contents (0.07 and 0.23 Wt-%) of rare earth (RE) element yttrium on cryogenic mechanical properties and fracture behavior of an Al-Li-Cu-Mg-Zr alloy has been studied at temperatures from 295 to 4 K. Y increased the yield strength, ultimate tensile strength, elongation, and notched tensile strength of the alloy at ambient and cryogenic temperatures. However, Y had less effect on the notch sensitivity and fracture toughness of the alloy. The better properties of the alloy can be obtained by addition of 0.23%Y. At peak-aged condition and cryogenic temperatures, the alloy (without Y) showed mixed fracture mode, the starting-fracture zone showed a cleavage-like fracture. Y addition improved the fracture resistance of the alloy, turned the mixed fracture mode into transgranular ductile fracture, and made the cleavage-like fracture in starting-fracture zone disappeared. The reasons of the improvements of properties and fracture resistance are attributed to the finer grains and S (Al2CuMg) phase homogeneous distribution induced by Y addition.
KeywordsFracture Toughness Ultimate Tensile Strength Slip Band Fracture Resistance Stress Concentration Factor
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