Microstructure and Hot Deformation Behavior of Extruded Mg-Li-AI-Y-Zr-Gd-Nd Alloy
The work aims to characterize the microstructure of the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy,conduct unidirec-tional hot compression experiments of magnesia-lithium alloy,study the thermal deformation behavior of the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy and establish a constitutive equation and machining diagram of the alloy.The microstructure of the extruded alloy was observed and analyzed by analytical testing methods such as SEM and EBSD.A single axis thermal com-pression experiment was carried out on the Gleeble-3500 thermal simulation experimental machine under conditions of strain rates from 0.001 to 1 s-1and deformation temperature from 200 to 350 ℃.Based on the dynamic material model,the power dis-sipation diagram and the instability diagram were superposed to obtain the thermal processing map,and the processing proper-ties of the extruded alloy were analyzed as a function of deformation temperature,rate and strain.The results indicated that the main phase in the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy was the β phase,with a small amount of fine α phase uniformly distrib-uted within the β phase.The true stress-strain curves of the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy under different deformation conditions all exhibited characteristics of dynamic recrystallization.As the deformation temperature decreased and the strain rate increased,the peak stress increased.The activation energy(Q)was 98 kJ/mol,and the stress exponent n had a value of 3.339 0.Through analysis with the thermal processing map,the formability of the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy increased with increasing strain.At strains of 0.1 and 0.3,there was an instability region in the processing map,which was related to incom-plete deformation of the alloy.At strains of 0.5,0.7,and 0.9,there was no instability region,and the alloy exhibited excellent formability.Considering the actual processing conditions of the extruded Mg-Li-Al-Y-Zr-Gd-Nd alloy,the optimal processing window for the allov is a deformation temperature range of 250 to 350 ℃ and a strain rate ranee of 0.01 to 1 s1.
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