【作者】 王威；

【导师】 孔凡涛；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2008， 硕士

【摘要】 随着TiAl合金实用化进程的发展,对TiAl合金板材制备以及其后续的热加工技术的需求越来越迫切。本文系统研究了Ti-43Al-9V-Y合金板材轧制过程中组织性能的演变;热处理对合金组织性能的影响;并初步探讨了Ti-43Al-9V-Y合金的超塑性。研究发现,经过不同道次的轧制,Ti-43Al-9V-Y合金显微组织已转变为主要由γ+B2相构成的双相组织,并有少量的α2相。轧制后,γ晶粒呈现等轴状,晶粒尺寸为5~25μm,B2相呈网络状包围在γ晶粒周围,随着轧制道次的增加,B2相中析出的γ相板条状组织含量增加,富稀土相颗粒分布越来越均匀、更加弥散,而且尺寸越来越小。抗压强度随着轧制道次的增加而增加。经过3道次轧制后,屈服强度最高,达到861MPa,6道次轧制后,屈服强度最低,进一步轧制,屈服强度逐渐升高。热处理后的Ti-43Al-9V-Y合金均由γ、α2、B2三相组成,但热处理对显微组织形貌影响较大。不同的热处理温度条件下,铸态、锻态和轧态合金相变形成的等轴γ晶粒、B2相及层片组织含量不同。其中轧态组织在1200℃及1250℃热处理组织变化不明显;1280℃热处理后,开始有层片析出;1300℃热处理时,形成双态组织;1320℃热处理时,层片组织大量降低,B2相大量生成,一部分高温α相降温过程中形成层片组织,另一部分α相降温过程中形成γ等轴晶。不同的热处理温度条件下,铸态、锻态和轧态Ti-43Al-9V-Y合金的力学性能发生显著变化。总体来说,轧态Ti-43Al-9V-Y合金热处理后的屈服强度较大;锻态Ti-43Al-9V-Y合金热处理后的压缩率较大;板材经过1320℃热处理硬度值最高,达到HV357。铸态Ti-43Al-9V-Y合金在900℃和950℃时拉伸,延伸率分别达到66.7%和17.0%。锻态Ti-43Al-9V-Y合金在900℃和950℃时拉伸,延伸率分别达到85.8%和102.2%,锻态合金在950℃拉伸时表现出超塑性。轧态Ti-43Al-9V-Y合金在900℃、950℃和1000℃时拉伸,延伸率分别达到15.1%、76.5%和100.1%。随拉伸温度的提高,塑性显著增加,轧态合金在1000℃拉伸时表现出超塑性。更多还原

【Abstract】 With the development of TiAl based alloys for high temperature structural applications, it is urgent to fabricate TiAl sheets and its hot working technology. This paper studied the microstructure and property evolution of Ti-43Al-9V-Y sheets during rolling, the effects of heat treatment on the microstructure and properties of alloys after different hot processings, and superplasticity of Ti-43Al-9V-Y alloys after different hot processings.It was found that the microstructure of the rolled Ti-43Al-9V-Y alloy shows two-phase structure,γphase and B2 phase, with a small amount ofα2 phase. After rolling, the morphology of phase grains is equiaxial with a grain size of 5 to 25μm. The morphology of B2 phase is reticulate encompassing theγphase grains. With the increase of rolling pass, the amount of precipitated lath-shaped phase from B2 phase increases, and the distribution of RE-riched phase is more homogeneous and more disperse. Their size is getting smaller. The compression strength increases with the increasing of rolling pass. After three rolling passes, the yield strength reaches a maximum, 861MPa. After six rolling passes, the yield strength drops to a minimum. With more rolling pass, the yield strength increases again.All the heat treatmented Ti-43Al-9V-Y alloys (as-cast, as-forged, as-rolled) consists ofγ、α2 and B2 phases. However, heat treatment has a significant effect on the microstructure of alloys. The amounts ofγequiaxed grains, B2 phases and lamellar structure after as-cast、as forged and as-rolled alloys phase changed with heat treatment temperature. The microstructure of as-rolled alloys showed no obvious difference between heat treatment temperature at 1200℃and 1250℃. After heat treatment at 1280℃, lamellar structure appeared at 1300℃. After heat treatment at 1320℃, duplex microstructure was obtained. During cooling, the amount of lamellar structure greatly reduced,with the formation of large amount of B2 phases. The high temperatureαphase partly transformed into lamellar structure, partly intoγequiaxed grains. At different heat treatment temperatures,there were significant change in mechanical properties of as-cast、as-forged and as-rolled alloys. Generally speaking,the as-rolled alloys show higher yielding strength; the as forged alloys show larger compressibility. After heat treatment at 1320℃, the hardness of the rolled sheets reached a highest, HV 357.The elongation of as-cast alloys reaches 66.7% and 17.0% at 900℃and 950℃, respectively. The elongation of as forged Ti-43Al-9V-Y alloys was improved to 85.8% and 102.2% at 900℃and 950℃, respectively. The as-forged alloys show superplasticity at 950℃., The elongation of as-rolled Ti-43Al-9V-Y alloys reaches 15.1%、76.5% and 100.1% at 900℃、950℃and 1000℃, respectively. With the increasing tensile temperature, plasticity increased significantly. The as-rolled alloys exhibit superplasticity at 1000℃更多还原