热处理对GH4169合金组织及650℃下低周疲劳性能的影响

Effect of heat treatment on microstructure and low cycle fatigue performance of GH4169 alloy at 650 ℃

采用两种不同热处理工艺对GH4169合金进行处理,观察并研究了合金的显微组织变化以及在5个应变幅(1.2%、1.0%、0.8%、0.6%和0.5%)和650℃条件下δ相对合金低周疲劳性能的影响。结果表明:随着900℃保温时间的延长,合金δ相的析出量增加。合金在高应变幅(Δεt/2≥0.6%)下的疲劳寿命基本不受δ相含量变化的影响;而在较小应变幅下(Δεt/2=0.5%)的疲劳寿命则具有一定的分散性,并随着δ相含量的增加而增加;与此同时,合金的塑性应变-寿命曲线在常温下具有的双线性特征在650℃高温下却不再具有,而且疲劳断口在相同应变幅下呈现出相似的形貌,裂纹源数量也随着应变幅的增加而增加。

GH4169 alloy heat-treated using different processes was employed to investigate microstructure variation of the alloy and the effect of δ phase on low cycle fatigue property of the alloy under strain amplitudes of 1. 2%,1. 0%,0. 8%,0. 6% and 0. 5% at 650 ℃.The results show that the amounts of δ phase of the alloy are increased as the extension of the holding time at 900 ℃. No significant influence of the amount of δ phase on fatigue life of the GH4169 alloy is observed under the high strain amplitude（ Δεt/2≥0. 6%）,the fatigue lives of the alloy after the two different heat treatments used in this paper are basically the same. However,when the experiment performed at low strain amplitude（ Δεt/2 = 0. 5%）,the fatigue lives show dispersive characteristics and increase with the increasing amount of δ phase. At the same time,the plastic stain amplitude-life curves of the alloy with bilinear feature at room temperature has not been found when the test temperature reached 650 ℃. Furthermore,the fatigue fracture at the same strain amplitude exhibits similar morphology,the number of crack sources observed from fatigue fracture surface increases with the increase of strain amplitude.