单晶高温材料中铸造微孔洞的扩长

基于有限变形晶体塑性本构关系及三维体胞模型,采用有限元的方法,分析了在不同应力三维度、不同罗德参数、不同滑移系开动及不同加载取向下,单晶高温合金中铸造微孔洞扩长的力学行为。分析结果表明:累积剪切应变在铸造微孔洞的扩长中起着很重要的作用,大的累积剪切应变对应高含量的铸造微孔洞;开动滑移系族的类型对铸造微孔扩长的影响不容忽视,故准确的确定开动滑移系的类型,对于评估单晶热端部件的寿命至关重要。由于不同的取向具有不同的Schmid因子、弹性模量及开动滑移系,单晶高温合金中的铸造微孔洞的扩长还与取向密切相关,因此根据热端部件工况,合理的选择其取向是有必要的。

Casting micro-porosity growth in single-crystal superalloys

Finite element(FE) analysis is employed to investigate casting micro-porosity growth in nickel-base single-crystal superalloys.Based on finite deformation rate-dependent crystallographic constitutive equation, the simulation of casting micro-porosity in three-dimensional unit cell model is carried out under variation in a range of parameters including triaxiality,Lode parameter,type of slip systems activated and Loading orientation.The FE results show that large local cumulative shear strain around casting micro-porosity plays an important role for driving casting micro-porosity growth,the high casting micro-porosity volume fraction corresponds to large cumulative shear strain.The type of slip systems activated has remarkable effect on casting micro-porosity growth,so it is very important to determine the operative slip systems for predicting the life of hot section.The growth of casting micro-porosity is related to crystallographic orientation,because different orientation is associated with different Schmid factor,the Young's modulus and slip systems activated.That is to say,according to load case of hot section,to choice a properly crystallographic orientation is necessary.