镍基单晶合金TLP焊接件破坏特性研究

Fracture characterization of the TLP welding specimen of a single crystal superalloy DD3

为研究镍基单晶合金的高温焊接性能,通过三点弯曲试验和扫描电镜对单晶体焊接件和单晶体试件在高温下的破坏机理进行了研究,并从晶体滑移理论出发,采用有限元方法对两种不同试样在相同载荷下的M ises应力分布和最大分切应力进行了数值分析.研究结果表明:对于采用TLP焊接连接的单晶焊接件,试样的破坏形式主要表现为脆性断裂,试样的抗弯强度明显低于单晶体试样;对于焊接连接的单晶体结构,由于焊缝处材料性质的差异,在焊缝附近出现明显的应力不连续性,对晶体界面附近的最大分切应力产生明显影响,引起界面附近分切应力分布梯度的显著增加,使试样的破坏特性发生改变,引起试样的脆性破坏,降低了试样的抗弯曲强度.

In order to study the welding characteristics of single crystal nism of the TLP welding specimen of single crystal superalloy DD3 and superalloy DD3, the fracture mechaoriginal DD3 specimen is studied with the three -point bending tests and SEM. Based on the single crystallographic theory, the distributing of the Mises stress and the maximum of resolved shear stress is analyzed by the FEM. The results showed that the welding specimen of single crystal superalloy DD3 changed more brittle than the original DD3 specimen and therefore the welding specimen had nearly half of the bending strength of original DD3 alloy. The numerical results of the Mises stress and the maximum of resolved shear stress proved that the w portant role in the models. Because of the material difference, the stress distribution elding line played an imchanged near the welding region, and the resolved shear stress concentrated very evidently near the welding line. Consequently, the brittleness of the single crystal welding specimen increased, the bending strength reduced.