A Study on Fatigue Properties of Sc and Zr Added Al Alloy

摘要

Al alloy is used extensively in several fields because specific strength is good and workability is superior. It is known that If Sc is added to Al alloy, strength is increased and re-crystallization temperature rises because microstructure becomes fine. The high cycle fatigue properties of four kinds of Al-Mg-Si alloys without and with only scandium of 0.20 % or with both scandium(Sc) of 0.20 % and zirconium(Zr) of 0.12% were investigated. The fatigue strength was determined at R = -1.0 under constant amplitude loading conditions in air. The alloy with scandium of 0.20 % showed a little higher fatigue strength values. The alloy with 0.20 % Sc and 0.12 % Zr showed highest tensile yield strength and highest fatigue strength. The fine grained Al 6061+0.20Sc+0.12Zr alloy exhibited a higher resistance against fatigue crack nucleation in comparison to the coarse grained Al 6061 alloy. The results can be explained mainly with the micro-structural differences among four alloys. This results are due to the presence of coherent Al_3 (Sc, Zr) precipitates and a very fine sub-grain structure.