镍基单晶高温合金CMSX-2原始树枝状晶中γ'相的定向粗化

DIRECTIONAL COARSENING OF γ' PRECIPITATES IN ORIGINAL DENDRITE REGIONS OF NICKEL-BASE SINGLE CRYSTAL SUPERALLOY CMSX-2

在760－1050℃和750－140MPa范围内，选择不同温度和应力的配合对CMSX－2合金进行持久拉伸至断裂，观察了试件原始树枝状晶各区域（枝晶干、枝晶臂及枝晶间）中γ’相的定向粗化及合金元素的分布特征结果表明，γ’的走向粗化程度在枝晶干内最大，在枝晶臂内次之，在枝晶间最小.在所有这些区域中，试验温度较高者的γ’定向粗化程度较大；各试件在持久试验后，γ形成元素W，Cr和Co，γ’形成元素Al和Ta，在原始树枝状晶结构中呈一定规律分布，分析了合金元素再分布对γ’定向粗化的贡献，试验温度、应力和时间与元素分布比的关系。

Sustaining tensile tests are carried out till the specimens fail by combining differenttemperatures and stresses over the range of 760 - 1050℃ and 750 - 140 MPa on nickel-base singlecrystal superalloy CMSX-2. Directional coarsening of γ' precipitates and distribution characteristics ofalloying elements in the original typical dendrite regions (dendrite core, dendrite arm and interdendrite) areobserved. The γ' directional coarsening extent is the most significant in the dendrite core region, and theless in the dendrite arm region, and the least in the interdendrite region, respectively. But, the γ' directionalcoarsening extent is more significant in all the typical regions at higher test temperatures. The γ formingelements (W, Cr and Co) and the γ' forming elements (Al and Ta) redistribute in a certain regularity in thetypical dendrite regions, which directly affects the γ' directional coarsening extent. Element redistributionexists in these regions near the fracture surface of the tested specimens, which is affected by the testcondition (temperature, externally applied stress and testing time) and also responsible for the specimenrupture life.