Ta含量对高性能镍基粉末高温合金高温拉伸性能的影响

使用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)和高温拉伸试验机等手段系统地研究了不同Ta含量FGH98合金的显微组织和高温拉伸性能。结果表明：添加Ta可明显消除原始粉末颗粒的边界(PPB，Prior Particle Boundary)，促进二次γ′相形态失稳和三次γ′相数量的增加。加入Ta使合金的高温抗拉强度和屈服强度都有一定程度的提高，Ta含量为2.4%(质量分数，下同)的合金塑性最好；无Ta和1.2%Ta合金的拉伸断口为结晶状断口；2.4%Ta合金的断口上有较多的等轴状韧窝，为韧性断裂；3.6%Ta和4.8%Ta合金为穿晶和沿晶解理断裂，属于典型的结晶状断口。在无Ta合金中产生大量孪晶和位错绕过γ′相发生变形，Ta的加入降低了合金的层错能，随着Ta含量的提高合金的位错剪切γ′相产生大量的层错。

Effect of Ta on High Temperature Tensile Properties of Advanced Ni-based Powder Metallurgy Superalloys

Microstructure and high temperature tensile properties of five powder metallurgy FGH98 alloys with different Ta content were systematically investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM) and high temperature tensile testing machine. The results show that: Ta can obviously eliminate the prior particle boundaries (PPB) and change the morphology of secondary γ'-phase. Ta can promote the generation of tertiary γ'-phase. Ta improved the high temperature tensile strength and yield strength of the alloys. When the Ta content was 2.4% (the same below), the alloy has the preferable plasticity. Alloys without Ta and with 1.2%Ta showed a crystalline-like fracture surface while the alloy with 2.4%Ta showed ductile fracture surface. Alloys with 3.6%Ta and 4.8%Ta exhibited transgranular and intergranular cleavage fractures. The alloy without Ta deformed mainly by generating a large number of twins and dislocations bypassing the γ'-phase. With the increasing Ta content, the dislocations shear the γ'-phase, therewith produce a large number of stacking faults.