应力时效对镍基单晶合金DD11组织及持久性能的影响

研究了1070℃/100MPa应力时效对镍基单晶合金DD11组织和持久性能的影响,通过扫描电镜和透射电镜对应力时效前后的组织进行了观察和分析,并对合金应力时效前后的持久性能进行了测试与分析。实验结果表明:应力时效前50h是形筏阶段,竖直方向的γ相通道逐步变窄或消失,水平方向的γ相通道宽度逐步增加,立方状γ′相在应力的作用下向水平方向扩展并相互连接在一起逐渐形成筏排形貌。应力时效50h后是筏排粗化阶段,随应力时效时间的延长,组织缓慢粗化,但是筏排形貌基本保持稳定。对应力时效后的组织进行1 070℃/140 MPa持久性能测试,结果表明,在形筏阶段持久寿命基本保持稳定,在筏排粗化阶段,持久寿命逐步下降。应力时效500h后,持久寿命由热处理后初始状态的360h左右降低至140h左右。研究结果表明,γ相通道尺寸的粗化和组织的筏排化是持久性能衰退的主要因素。

Effect of stress aging on the microstructure and stress-rupture properties of a single crystal superalloy DD11

The effect of uniaxial stress aging at 1 070 ℃/100 MPa on the microstructural evolution and the stress rupture properties of a single crystal supperalloy DD11 was investigated.The microstructure before and after the stress aging was observed with scanning electron microscope and transmission electron microscope,and the stress rupture properties before and after the stress aging were also tested.The experiment results show that the evolution of the microstructure can be divided into two stages,rafting (first 50 h) and coarsening (after the first 50 h) of the rafting microstructure.At the first stage,the vertical direction of the γ phase channels becomes narrow or disappears gradually,and the width of horizontal direction of the γ phase channels increases gradually.At the same time,the cuboidal γ'phase expands horizontally and gradually connects with each other.At the second stage,the dimension of the rafts coarsens slightly.However,the morphology of rafting keeps stable.The stress rupture properties of 1 070℃/140 MPa decrease slightly at first stage and degrade gradually at second stage.After stress aging for 500 h,the stress rupture properties decline from initial 360 h to 140 h.The results show that the key factors for the degeneration of the stress rupture properties are the coarsening of the matrix channels and the rafting of the microstructure.