文档介绍：摘要
本文采用Md法和Nv法设计了2种不同Re含量的单晶镍基合金,并对合金中析出TCP相的倾向进行了预测和验证。通过对制备的单晶合金进行热处理、蠕变曲线测定及组织形貌观察,研究了热处理、TCP相对单晶合金蠕变行为的影响。
结果表明,确定出Md和Nv方法预测含Re镍基合金中有TCP相析出的临界值分别为:Md > > ;%Re合金在高温时效期间,有TCP相沿{111}<110>取向呈片状析出,随时效时间延长,TCP相可转变成球状形态。%Re合金经1320℃高温固溶处理,可大幅度降低合金中枝晶间/臂区域的成分偏析,经高温固溶冷却后,合金中的g′相呈现组合碟形形态,经1100℃时效后,µm的立方g¢相以共格方式嵌镶在g基体中,随时效温度提高,g¢相已过分长大。%Re合金相比,%Re合金在中温高应力蠕变期间无TCP相析出,具有较好的蠕变抗力,其变形机制是位错剪切g¢相,其中,切入g¢相内的<110>超位错发生分解,形成(1/3)<112>超肖克莱不全位错加层错的位错组态,可抑制位错的交滑移,是使合金具有较好蠕变抗力和较长蠕变寿命的原因。在高温蠕变期间,%Re合金中有TCP相析出,由于TCP相发生球化转变,仅较小幅度降低合金的蠕变寿命。%Re合金相比,%Re合金在高温低应力下有较好的蠕变抗力和较长的蠕变寿命,主要原因是,蠕变期间形成具有较高强度的筏状g¢相与应力轴方向垂直,可有效阻碍位错运动。%Re合金在高温低应力蠕变期间,在最大切应力作用下,迹线方向为[0`11]和[011]的超位错切入筏状g¢相,其中,主次滑移系交替开动,使筏状g¢相扭折,位错剪切g¢相的数量增加,直至发生蠕变断裂,是合金在蠕变后期的主要变形机制
关键词:单晶镍基合金;元素Re;TCP相;蠕变;组织演化
Influence of the element Re on microstructure and creep properties of nickel-based superalloys
Abstract
In this dissertation, by means of Md and Nv method, two positions of the single crystal nickel-based superalloys containing Re have been designed to predict the precipitated tendency of TCP phase, and investigating the effects of the heat treatment regimes and TCP phase on the microstructure and creep behaviour of the single crystal nickel-based superalloys by means of the heat treatment, creep curve measurement and microstructure observation.
The results show that positions of the superalloys may be designed to forecast the precipitated tendency of TCP phase by means of Md and Nv method, and the critical value of TCP phase precipitated are determined to be Md > and Nv > , respectively. In the further, the slice-like TCP phase in %Re single crystal nickel-based superalloy during high temperature aging is precipitated along {111}<110> orientation, and the TCP phase is transformed into the sphere-like morphology as the aging time prolongs. The solution treatment of %Re single crystal superalloy is made for 4 h at 1320℃, which may reduce position segregation in the d