TA15合金大型筋板件等温局部加载晶粒尺寸演化研究

Numerical simulation of microstructure evolution of TA15 alloy large-scale rib-web parts during isothermal local loading process

随着航空工业的迅速发展,大飞机和新一代军机的研制,钛合金大型筋板件的应用日益广泛,等温局部加载技术为该类构件的成形提供了新的途径。然而,等温局部加载成形是一个多因素耦合作用下的复杂成形过程,工艺参数控制不当将产生粗晶、组织不均匀等缺陷。为此,文章采用内变量法,建立了TA15合金高温变形微观组织演化物理模型,并与有限元软件DEFORM 3D结合对TA15合金筋板件等温局部加载成形过程等轴α相晶粒尺寸演化进行数值模拟。结果表明,锻件先加载区、后加载区及变形过渡区晶粒尺寸基本一致;随着温度的升高,锻件等轴α相晶粒尺寸平均值,呈先减小,后增加的趋势;锻件等轴α相平均晶粒尺寸随模具运动速度增加,先快速减小,后趋于平缓,较大的模具运动速度易造成组织不均匀性增加;采用只局部加载的加载方式,可以获得比采用先局部后整体的加载方式,更均匀细小的组织。

With the rapid development of big airplane and new generation military airplane in aviation industry, there is an increasing application for titanium large-scale rityweb parts. Isothermal local loading forming provides a new way to form them. However, it is a multi pass process and the material undergoes complex uneven deformation and microstructure which is influenced by many factors which will influence the size and distribution of primary a grain. Therefore, predicting and controlling mi- crostructure evolution are key problems in isothermal local loading process. A set of equations describing microstructure evolution of TA15 alloy are developed using internal state variable method and are implemented in FE software to investigated the microstructure evolution in isothermal local loading process. The results show that there is no distinct difference of the size and distribution of primary a grain in the first-loading region, second loading region and the transition region. The size of primary a grain decrease first with increasing deformation temperature and the increase; The size of primary a grain decreases rapidly at first with increasing loading speed, then becomes steady. High loading speed will increase inhomogeneity of the distribution of primary orphase grain size; Adopting only local loading mode can obtain workpiece with more homogeneous and smaller microstructure than adopting whole loading after local loading mode.