Diffusion Bonding and the Optimization of An Oxide Dispersion Strengthened Ni-base Alloy

研究了氧化物弥散强化镍基合金MA758的扩散连接，结合和控制了一些连接参数和微观组织。结果表明：(1)焊后再结晶处理是改善接头高温性能的关键。(2)存在获得良好接头的最佳结合压力：当扩散结合压力过低时，存在非结合区域。另一方面，当其过高时，焊接界面保留了未充分长大的非再结晶区域，降低了接头的力学性能。(3)有限元分析表明，结论(2)中所示的未再结晶区域的保留，一定是由于塑性变形过大而导致材料失去了足够的晶粒长大所需的内部应变能。对粘结件的形状进行了改进，避免了残留的非再结晶区域。采用改进的几何形状和最佳的焊接条件生产的接头，其疲劳强度几乎与母材相当。

Diffusion bondings of an oxide dispersion strengthened Ni-base alloy, MA758 was studied, combining and controlling some bonding parameters and the microstructures. The high temperature fatigue strength of the joints optimized was also investigated, compared with those of base materials.The conclusion reached are sumarized as follows :(1) The post weld recrystallization treatment was found to be essential to improve the properties of the joints at high temperatures.(2) There is the best bonding pressure to obtain good joint : When the diffusion bondeing pressure was too low, non-bonded region remained. On the other hand, when it was too high, a non-recrystallized region with inadequately growing grains was retained at the welded interface, which reduced the mechanical properties of the joints.(3) The FEM analysis indicated that the retained non-recrystallized region show in the conclusion(2), must be resulted from the too large plastic deformation which would take away internal strain energy for adequate grain growth from the material. The shape of bonding component to avoid the retained non-recrystallized region was improved and proposed. The joints produced by employing the improved geometry and the optimum welding condition, revealed the fatigue strength almost comparable to that of the base material.