一种镍基单晶合金高温蠕变期间的变形特征及元素分布

Element Distribution and Deformation Characteristics of a Single-crystal Nickel-based Alloy During High-temperature Creep

通过对一种6%Re/5%Ru镍基单晶合金进行高温蠕变性能测试、组织形貌观察及三维原子探针成分分析,研究了合金高温蠕变前后的元素分布及蠕变过程中的变形特征。结果表明,完全热处理后Al和Ta元素主要分布在合金的γ′相中。合金在1120℃/165 MPa条件下蠕变断裂后,元素在γ/γ′两相的分布发生改变,其中,Al、Ta、Cr和Co因为氧化作用导致在γ/γ′两相中的浓度均降低。此外,一部分Re、Ru、W和Mo原子富集于γ/γ′相过渡区域附近的γ基体一侧,可引起晶格畸变,增加位错运动的阻力,延缓位错剪切进入γ′相,是含Re/Ru合金具有较好高温蠕变抗力的原因之一。蠕变后期,切入相的位错可由{111}面交滑移至{100}面形成K-W锁,其保留的高数量K-W位错锁可抑制位错滑移和交滑移,是合金有较好蠕变抗力的原因之一。

Through a high-temperature creep performance test,microstructure observation,and three-dimensional atom probe composition analysis of a 6%Re/5%Ru(mass fraction)single-crystal nickel-based alloy,the element distribution before and after the alloy creep under high temperatures and the deformation characteristics during creep were studied.The results showed that the Al and Ta elements were mainly distributed inγ′phase of the alloy after complete heat treatment.After creep fracture at 1120℃/165 MPa,the distribution of elements inγ/γ′phase changed.Among them,the concentration of Al,Ta,Cr and Co in theγ/γ′two phases was reduced due to oxidation.In addition,some Re,Ru,W and Mo atoms were expelled fromγ′and enriched on the side of theγmatrix near theγ/γ′phase transition region,which could cause the lattice distortion to increase the resistance of dislocations motion and delay the shearing of dislocations into theγ′phase.It was one of the reasons why Re/Ru alloys have better high temperature creep resistance.In the later creep stage,the dislocations of shearing intoγ′phase may cross-slid from{111}to{100}planes to form the K-W dislocation locks,and the K-W dislocation locks with more amount may inhibit the sliding and cross-sliding of dislocations to improve the resistance of alloy,which was thought to be one of the reasons of the alloy having better creep resistance.