横向预压缩对[001]取向镍基单晶高温合金蠕变性能的影响

Effect of Transverse Pre-compression on High-Temperature Creep Behavior of a [001]-Oriented Single Crystal Nickel-Based Superalloy

通过蠕变性能测试及组织形貌观察,研究了预压缩对一种[001]取向镍基单晶合金蠕变性能的影响。结果表明,[001]取向镍基单晶合金在1040℃/180 MPa条件下沿[100]方向预压缩38 h后,立方??相转化为与[001]取向垂直的P型纤维状筏形组织。合金晶向及预压缩和拉伸蠕变应力轴取向误差是预压缩合金内纤维状??相发生横向连接的原因。合金在预压缩及后续拉伸蠕变过程中??/?相界面能的降低是??相发生组织演化的驱动力。有/无预压缩的[001]取向合金在980℃/200 MPa条件下蠕变至稳态阶段的变形机制为位错在基体通道内的滑移和攀移。相对于未预压缩合金,预压缩后合金的微观组织结构使位错更容易在基体通道中滑移,其对合金沿[001]方向的应变率贡献更大,因此预压缩降低了合金在980℃/200 MPa条件下的蠕变抗力。

By means of creep tests and microstructure observations, the effect of transverse pre-compression on high-temperature creep behavior of a [001]-oriented single crystal nickel-based superalloy was studied. Results show that after being pre-compressed along [100] orientation at 1040 oC/180 MPa for 38 h, the cuboidal ？？ phase transforms into one-dimensional P-type stripe-like rafts perpendicular to the [001] orientation. The misorientations of the alloy and stress axis of pre-compression/tensile creep are responsible for the transverse connection of the stripe-like ？？ rafts. The decrease of the interfacial energy of ？？/？ phases is the driving force of the microstructure evolution during the pre-compressive treatment and the subsequent tensile creep test of the alloy. The deformation mechanism of the [001]-oriented alloys with and without pre-compression during steady-state creep at 980 oC/200 MPa is dislocations gliding and climbing in ？ matrix channels. Compared to the alloy without pre-compression, the microstructure of the pre-compressed alloy makes the dislocation slip in matrix channels more easily, which has more contributions to the strain rate of the alloy along [001] orientation, so the pre-compression decreases the creep resistance of the alloy at 980 oC/200 MPa.