In-situ study of the microstructure evolution during tension of a Mg-Y-Zn-Al alloy processed by rapidly solidified ribbon consolidation technique

Mg-Y-Zn-Al alloys processed by rapidly solidified ribbon consolidation(RSRC)technique exhibit an exceptional mechanical performance indicating promising application potential.This material has a bimodal microstructure consisting of fine recrystallized and coarse non-recrystallized grains with solute-rich stacking faults forming cluster arranged layers(CALs)and nanoplates(CANaPs),or complete long period stacking ordered(LPSO)phase.In order to reveal the deformation mechanisms,in-situ synchrotron X-ray diffraction line profile analysis was employed for a detailed study of the dislocation arrangement created during tension in Mg-0.9%Zn-2.05%Y-0.15%Al(at%)alloy.For uncovering the effect of the initial microstructure on the mechanical performance,additional samples were obtained by annealing of the as-consolidated specimen at 300 and 400℃ for 2 h.The heat treatment at 300℃ had no significant effect on the initial microstructure,its evolution during tension and,thus,the overall deformation behavior under tensile loading.On the other hand,annealing at 400℃ resulted in a significant increase of the recrystallized grains fraction and a decrease of the dislocation density,leading to only minor degradation of the mechanical strength.The maximum dislocation density at the failure of the samples corresponding to the plastic strain of 10-25% was estimated to be about 16-20×10^(14)m^(-2).The diffraction profile analysis indicated that most dislocations formed during tension were of non-basal and pyramidal types,what was also in agreement with the Schmid factor values revealed independently from orientation maps.It was also shown that the dislocation-induced Taylor hardening was much lower below the plastic strain of 3% than above this value,which was explained by a model of the interaction between prismatic dislocations and CANaPs/LPSO plates.