单晶镍基合金在拉伸蠕变期间的组织演化与分析

Microstructure Evolution and Analysis of a Single Crystal Nickel-Based Superalloy during Tensile Creep

摘要:

通过[001]取向镍基单晶合金拉伸蠕变期间的组织形貌观察，采用应力应变有限元方法计算出立方γ/γ′两相共格界面的von Mises应力分布，研究了合金在蠕变期间γ′相的定向粗化规律。结果表明，施加拉应力可改变立方γ/γ′两相的应力分布，使不同晶面发生晶格收缩与扩张应变，其中，（001）晶面产生晶格收缩可排斥较大半径的Al、Ti原子，（100）和（010）晶面沿平行于应力轴方向产生晶格扩张应变，可诱捕较大半径的Al、Ti原子，是使其γ′相沿扩张晶格的法线定向生长成为类似筛网层状结构的组织演化规律。并进一步提出蠕变期间发生元素扩散和γ′相定向生长的驱动力。

Abstract:

The microstructure of a [001] orientated single crystal Ni-based superalloy was observed during tensile creep. By the stress-strain finite element method (FEM) for calculating the von Mises stress distribution in the coherent interface of the cubic γ/γ′ phases, the influence of the applied stress on the regularity of γ′ phase directional coarsening was investigated. Results show that the distribution of the von Mises stress in the cubic γ/γ′ interfaces is changed by the applied tensile stress, which may bring the lattice contraction or expanding of the various crystal planes in the cubical γ′ phase. Thereinto, the lattice contraction strain on (001) plane may repel the Al and Ti atoms with bigger radius, while the lattice expanding strain on (100) and (010) planes may trap the Al and Ti atoms to promote the directional growth of γ′ phase into the mesh-like layer structure along the normal of the expanding lattice. This is thought to be the regularity of γ′ phase directional coarsening during creep of the alloy. Furthermore, the driving force of the elements diffusing and γ′ phase directional coarsening was proposed.