【摘要】 采用Gleeble-1500D热压缩模拟试验机研究了铸态Ti-43Al-9V-Y合金在1100—1225℃,应变速率0.01—1.0 s^-1条件下的高温变形行为.根据测得的真应力-真应变曲线,基于动态材料模型（DMM）建立了Ti-43Al-9V-Y合金的热加工图.结果表明,在高应变速率区,合金易发生楔形开裂;在1150℃,0.01 s^-1条件下,合金发生了α+β+γ→β+γ相变;在1200—1225℃,0.01—0.05 s^-1条件下,合金发生了动态再结晶,具有一定的超塑性,组织为均匀细小的γ晶粒,此时最适于进行热加工.研究发现,1225℃处于α单相区,高温无序α相良好的变形能力是改善合金热加工性能的主要原因.锻造后的合金同时具有良好的断裂韧性和室温塑性.在室温下,Ti-43Al-9V-Y合金中的B2相可以起到阻碍裂纹扩展的作用,而不降低合金的塑性.更多还原

【Abstract】 The hot deformation behavior of as-cast Ti-43A1-9V-Y alloy has been studied using thermo-simulator system Gleeble-1500D in the temperature range 1100—1225℃ and strain rate range 0.01—1 s^-1.It was found that the flow behavior of Ti-43A1-9V-Y alloy depends on the deformation temperature and strain rate.The flow stress-strain curves exhibit oscillations in the stage of flow softening.According to principles of dynamic materials modeling（DMM）,processing maps were constructed on the basis of flow stress data.Wedge cracking was expected to be observed in the region of high strain rates with low peak efficiency（<40%）.The α+β+γ→β+γ phase transformation occurring at 1150℃ and 0.01 s^-1 contributes to the peak efficiency of around 60%.The dynamic recrystallization occurred at 1200—1225℃ and 0.01—0.05 s^-1 with a peak efficiency of around 80%, which is the optimum condition for the hot deformation of Ti-43A1-9V-Y alloy.Combining with the titanium and aluminum phase graphs,it could be found that 1225℃ located at the single-phase region of α phase.The excellent hot deformability of disordered α phase is considered to be the main reason for the improvement of hot workability of TiAl alloys.As-forged alloys have good room-temperature ductility and fracture toughness simultaneously.In addition,it has been found that B2 phase could hinder the propagation of crack without decreasing the plasticity at room temperature.更多还原