Effect of heat treatments on microstructure and mechanical properties of 2195 Al-Li alloy
2195 Al-Li alloy sheets at T8 state were treated by solution treatment(430,450,470,490 and 510 ℃)and aging treatment(18,24 and 36 h).The tensile strength and elongation of the alloys after solution and aging treatments were measured by tensile test at room temperature.The tensile fracture and microstructure were observed by SEM,XRD,EBSD and TEM.The results show that the saw-tooth flow phenomenon exists in the stress-strain curves after solution treatment,but disappears after aging treatment,which is attributed to Porterin-Le Chatelier(PLC)effect.Solution treatment can effectively improve the plasticity of the alloy,and aging treatment can improve the strength of the alloy.Further analysis on microstructure changes during solution and aging processes shows that β'phase does not par-ticipate in solution and aging precipitation,and the increase of strength after aging treatment is due to precipitation strengthening and dis-persion strengthening caused by precipitation of θ'phase and δ'phase.
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