Effect of Sc on Microstructure Evolution and Mechanical Properties of Cast Al-Li Alloy
The effects of Sc alloying on microstructure evolution and mechanical performance of Al-Li-Cu-Mg alloy were investigated.The results indicate that 0.2%Sc addition has significant effect on grain refinement of the alloys.Meanwhile,Sc alloying obviously enhances the precipitation density of the core/shell composite particles in as-aged alloy.Sc-containing alloy exhibits excellent matching of strength and plasticity at room temperature and 200℃ ,which is attributed to the synergy of the grain refining strengthening and precipitation strengthening(δ′-Al3Li phase and core/shell composite structure particles).When the temperature is increased to 300℃ ,the strength of Sc-containing alloy is decreased sharply,while elongation is increased significantly due to the grain boundary weakening effect.The fracture morphology observation reveals that the fracture mode of the reference alloy presents quasi cleavage fracture at room temperature,which is stable with the variation of temperature.The fracture mode of Sc-containing alloy at room tem-perature is characterized by intergranular fracture,which is transformed to mixing fracture of intergranular and trans-granular at 200℃ ,and microporous aggregation fracture at 300℃ .
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