单晶镍基高温合金在600～760℃下的低循环疲劳行为

摘要

研究[001]晶体取向的第二代单晶镍基高温合金DD6中温段下的低循环疲劳行为,实验温度为600 ℃,650 ℃, 700 ℃和760 ℃,应变比为–1.结果表明:在此温度范围内,合金呈现循环硬化特性;随着温度的升高,[001]晶体取向DD6合金的弹性模量有所降低,合金的应变-寿命关系与温度相关.采用考虑温度影响修正的循环损伤累积(CDA)模型对[001]晶体取向DD6合金在中温段下的低循环疲劳寿命进行统一预测,预测寿命值位于实验结果的±3倍分散带以内.%Low cycle fatigue (LCF) tests were conducted on a single crystal nickel-based superalloy DD6 with crystallographic orientations [001] at different elevated temperatures. The typical temperatures selected are 600 ℃, 650 ℃, 700 ℃ and 760 ℃, which represent the temperature field of turbine blade root or dovetail. The experimental results indicate that the characteristic of cyclic hardening exists in DD6 superalloy at middle temperature range. The LCF strain range-life curves are temperature-dependent. A modified cyclic damage accumulation (CDA) life prediction model is proposed. In this modified model, an approximate logarithmic linear function is introduced as the additional terms to consider the temperature effect. The prediction results are mainly distributed in scatter band of ±3. The temperature-modified CDA models agree well with the experimental data.