The effects of different content of Sc addition on the
microstructure and properties of the Al-4Cu alloy were studied by
tensile tests, optical microscope, X-ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experiment results show that rare-earth element Sc is capable of refining the dendrite structure of the Al-4Cu alloy and the strength of the alloy depends on Sc
content.The tensile strengh σ b and yield strengh σ 0.2 of the alloy increase a little for Sc content lower than 0.2%; and slightly decrease for increasing Sc content to 0.3%～0.4%.σ b and σ 0.2 of the alloy rise again when the Sc content is 0.5%, though both of them are lower than that of the Al-4Cu alloy without Sc addition. However, no significant influence of Sc addition on the elongation of the Al-4Cu alloy is observed. Adding Sc to the Al-4Cu alloy, Sc mostly traps into the α-Al solid solution for Sc content lower than 0.2%.However, when the Sc content is at the range of 0.3%～0.5%, only a part of Sc traps into the α-Al solid solution, others form Al 3Sc,which can strengthen the alloy, and AlCuSc phase, which is harmful to the Al-Cu-Sc alloy.