Effects of pre-deformation on grain refinement and superplasticity of 2050 Al-Li alloy

Abstract

Fine-grain 2050 Al-Li alloy sheets were prepared by thermomechanical treatment processing(TMTP). The effects of pre-deformation on second phase distribution, grain structure and superpl-asticity of alloy sheets were studied by optical microscope and scanning electron microscope. The results show that after pre-deformation, a large amount of subgrains are formed in the plate during high temperature overaging. A large number of subgrain boundaries promote the precipitation of TB phase and increase the roughening rate, which significantly increases the size of intragranular TB phase. The volume fraction of second phase particles that effectively stimulates recrystallization nucleation increases from 0.92% to 3.28%. Compared with the non-predeformed sheets, the average grain size of the center layer of the sheets is reduced from 12.59μm to 9.59μm, the average grain size of the surface layer is reduced from 10.79μm to 8.60μm, the grain refinement effect is obviously improved, the superplastic deformation ability is significantly improved. The elongation of superpla-stic deformation increases from 230% to 470% under the condition of 490℃ and 2×10-4s-1.

Keywords

• 2050 al-li alloy
• grain refinement
• thermomechanical treatment
• particle-stimulated nuclea-tion
• superplasticity