Optimization of Secondary Crystallographic Orientation of Ni-based superalloy single crystals

本文利用一种表现出不同活动滑移系的实验高温合金单晶，研究了初晶和二晶取向对镍基高温合金单晶蠕变和疲劳强度的影响。在{111}&lt；101&gt；和{111}&lt；112&gt；滑移系的假设下，讨论了晶体取向和塑性各向异性对镍基高温合金单晶蠕变和疲劳强度的影响。{111}&lt；112&gt；滑移是不寻常的滑移。对于靠近[001]轴的拉应力，(-111)[1-12]滑移系是本征-外在超晶格层错对通过γ相的结果。在接近[011]的拉伸方向，(111)[-211]滑移是通过γ和γ‘相的孪生剪切发生的。在蠕变强度方面，结果与一次蠕变中的{111}&lt；112&gt；滑移和二次蠕变中的{111}&lt；101&gt；滑移的假设一致。The n…在850℃，20h的附加时效抑制了{111}&lt；112&gt；滑移系统的活动，从而影响了更多的咬合蠕变行为。疲劳寿命和裂纹扩展行为取决于由{111}和lt；101&gt；滑移系排列引起的塑性各向异性和应力状态。本文报道了三种合金：TM 82+，CMSX-4和TMS 75，分别含有2.4，3.0和5.0wt%Re的一次蠕变应力依赖性的初步研究结果。蠕变试验是在一定的应力范围内对从单个棒材上切割的试件进行的；选择与[001]成8-12°的取向是为了促进合理的初始蠕变量，并在整个合金系列中提供取向的一致性。研究发现，随着合金中Re和Co含量的增加，一次蠕变量增加，并且对于每种合金，都确定了出现不同的一次蠕变的应力门槛。位错变形机制的电子显微镜观察表明，随着原生蠕变的增加，层错剪切的发生率增加。位错穿透γ相的程度和可移动位错带的构型的显著差异表明，控制移动性和硬化的因素共同导致了高的一次蠕变。较少

In this study, by using single crystals of an experimental superalloy which shows distinct active slip systems, the influence of primary and secondary crystal orientation on creep and fatigue strengths of Ni-based superalloy single crystals was investigated. The influence of crystallographic orientations and plastic anisotropy on the creep and fatigue strengths of single crystals of the Ni-base superalloy was discussed on the assumption that {111}<101> and {111}<112> slip systems. {111}<112> slip is unusual slip. For a tensile stress applied close to the [001] axis, (-111)[1-12] slip system is result of pass of intrinsic-extrinsic superlattice stacking faults pair through the γ phase. In the tensile orientation close to [011], (111)[-211] slip is occurred by twinning shear through γ and γ' phases. In the case of creep strength, the results were in agreement with the assumption of the operation of the {111}<112> slip in the primary creep and {111}<101> slip in the secondary creep. The n … More otched creep behavior was found to be influences by the additional aging at 850℃ for 20 h, which prohibited activity of {111}<112> slip systems. The fatigue lifetime and crack growth behavior depended on both plastic anisotropy caused by arrangement of {111}<101> slip systems and the stress state.We report some preliminary results of a systematic study of the stress dependence of primary creep in three alloys: TMS82+, CMSX-4 and TMS 75, containing 2.4, 3.0 and 5.0 wt % Re respectively. Creep tests were performed at a range of stresses on specimens cut from a single bar; orientations between 8-12° from [001] were chosen to promote a reasonable amount of primary creep and provide consistency in orientation across the series of alloys. It has been found that the amount of primary creep increases as the amounts of rhenium and cobalt in the alloys increase, and for each alloy a stress threshold for the occurrence of a distinct regime of primary creep is identified. TEM observations of the dislocation mechanism of deformation show a higher occurrence of stacking fault shear with increasing primary creep. Considerable differences in the extent of dislocation penetration into the γ phase and in the configuration of the mobile dislocation ribbons point to a combination of factors governing mobility and hardening being responsible for high primary creep. Less