小偏离度对[001]取向单晶高温合金蠕变性能的影响

Influence of Small Misorientation from [001] on Creep Properties of a Ni-Base Single Crystal Superalloy

用选晶法制备了[001]取向的Ni-Co-Cr-Mo-W-Al-Ti-Ta镍基单晶高温合金板坯,从板坯上切取偏离[001]取向一定角度的持久试样,偏离度在20°以内。在750℃/750 MPa的低温高应力条件下,偏离不同角度的试样均获得了较长的蠕变寿命和较低的应变量,进入稳态阶段之前不同偏离度试样之间的初始蠕变量具有一定的差别,但稳态阶段各试样的应变速率基本相同,所以偏离度对整个试样的蠕变寿命影响不大。各取向共同的变形特征是γ′相中形成大量层错,基体通道中有大量的位错堆积,但具体的位错及层错组态有所不同。在偏离[001]取向20°以内,偏离度对微观组织演化、变形机制的影响不明显。

The slab of Ni base single crystal superalloy was fabricated in [001] orientaion by selector technique.This slab was cut into stress rupture samples of which orientaion deviate from [001] within 20°.Under low temperature 750 ℃ and high stress 750 MPa condition,all samples with various misorientation acquire long creep lives and small creep strains.Although their primary creep strains are different,their creep rates in steady creep are equal roughly.Therefore,misorientations within 20° have little influence on whole creep lives.The common deformation feature of samples with different misorientation is formation of numerous stacking faults in γ′ phase and entangling large quantities of dislocations in matrix,while their configurations are different in detail.When the misorientation is smaller than 20°,it can only produce a little effect on microstructure evolution and deformation mechanism.