Study On The Thermal Treatment And Thermal Deformation Of Mg-11Gd-2Y-0.4Zr Alloy

In this paper, Mg-11Gd-2Y-0.4Zr alloy was chosen as the study object. Fristly, the alloywas treated in solid solution and an prescription treatment. And secondly, we make Hotextusion on the thermal treated alloy with different temperature in Gleeble-1500D experiment.The last, hot working chart and constitutive equations were described. Microstructures undereach condition were analysed. Conclusions were as follows:The second phase in the original microscopic structure of the Mg-11Gd-2Y-0.4Zroriginal extruded magnesium alloy were observed that it mainly formed a net tructure alongthe crystal boudary. Acicular ordered structure was seen in the crystal grain and its directionwas different in different grains. It was showed solution into basic matrix grains by themetallographic analysis after thermal treatment that the alloy’s optimum condition wasachieved under 510℃（treatment time 24h）; Judged by the peak stress, aging temperature andtime should be set as 225℃and 18h. Under this condition, the highest aging peak hardnesswas 72.2HRB.In thermal extrusion between 320℃～480℃, it could be seen from the curves with strainrate from 0.001s^-1～1s^-1under various deformation temperature that the flow stress roserapidly with the strain. While the true strain was over some value, as the continuousincreasing strain, obvious change of true stress did not appear, which exhibited a steady stateand obvious strain peak value was showed. Soon afterwards, true stress fell off suddenly, andstrain-discontinuous-yielding phenomenon was observed. The alloy’s peak flow stressequation of thermal compression deformation was calculated by the peak stress value.In the certain strain conditions, the processing maps display materls power dissipationvalue and the instability distribution which is the two-dimensional space of strain rate and temperature. It was indicated by the research that the alloy’s dynamic recrystallization zonewas the processing zone between 420℃～470℃with 0.01s^-1～0.001s^-1stress rate. Underthis condition, the corresponding energy dissipation efficiency ratio was between 30% and 40%, which was easy to process the alloy.