摘要
研究了镍基单晶高温合金DD10在760℃和980℃条件下低周疲劳过程中的拉-压不对称性行为,并对其机制进行了深入探讨。结果表明,在疲劳试验初期,当应变幅较低时,在两种温度条件下拉-压不对称性都不明显,且拉力略大于压力;随着循环周次或应变幅的增加合金的拉-压不对称性逐渐明显,在760℃时拉力明显大于压力,而在980℃时拉力却明显小于压力。循环初期的拉-压不对称性行为与基体应力状态有关,而在大应变幅下和循环应力稳定阶段拉-压不对称性的正负属性和程度与位错在不同温度拉伸和压缩过程中克服γ′粒子的运动方式不同有关。
The main objective of the present research aims at investigating effects of the cyclic number, temperature and strain amplitude on the tension-compression asymmetry behavior of single crystal(SX) superalloy DD10. Fully reversed LCF tests with Rε=-1 are conducted at 760℃ and 980℃ under various strain ranges, and some tests are interrupted after the 1st cycle and at the cyclic stress saturation stage to figure out the evolution of the tension- compression asymmetry and the dislocation configurations. Results show that this asymmetry behavior is affected by several factors, such as the stress field in matrix, temperature and the strain range, and these factors depict various effects in different parts of the LCF process. In the 1st cycle, the K value(the ratio of stto sc) is slightly above 1 in low strain range for both temperatures, due to the compress in matrix resulted from the negative lattice mismatch. With the increment of strain amplitude or cyclic number, the tension-compression asymmetry gets much severer: at760℃ the K is above 1, whereas at 980℃ K is below 1. TEM observations reveal that this distinct asymmetry behavior arises mainly from the different motion modes of dislocations in γ′ phase, e.g. perfect dislocations at 760℃ and stacking fault at 980°C.
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2014年第7期535-540,共6页
Chinese Journal of Materials Research
基金
国家重点基础研究发展计划项目2012AA03A513
国家自然科学基金项目51101160和51171193资助~~
