摘要
研究了新型镍基高温合金Ｕ７２０Ｌｉ在６５０和７００℃时织织稳定性、蠕变行为和变形机制，结果表明，在长期时效过程中，初生γ＇相，二次γ＇相以及晶界析出相的形态几乎不发生变化，三次γ＇相经历一个粗化长大和溶解消失的过程，在６５０℃蠕变过程中，蠕变第一阶段的形变量随着施加应力的增加单调增大，而在７００℃蠕变时，蠕变第一阶段的形变量随着施加应力的增加先降后升，合金６５０和７００℃蠕变断裂寿命和最小蠕变速率在低应力区和高应力区服从于不同斜率的双对数线性规律． 在高温低应力下，合金的蠕变机制为位错攀移机制，而在低温高应力下，蠕变过程由位错切割机制控制．
Microstructural stability creep behavior and deformation mechanisms have been investigated on nickel base superalloy U720Li at 650 and 700 degreesC. The results show that the primary and secondary gamma' particles as well as grain boundary phases maintain good thermal stability at 650-700 degreesC with aging time up to 3000 h, while the tertiary gamma' particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with increasing of aging time and temperature. The primary creep strain at 650 degreesC increases monotonously with increasing of applied stress, while the primary creep strain at 700 degreesC decreases with increasing of applied stress below 550 MPa, and increases with increasing of applied stress above 550 MPa. Rupture lives and minimum creep rate at 650 and 700 degreesC fit double logarithmic relationship with different slopes at lower stress and high stress zones. Deformation mechanism under high temperature and low stress is attributed to dislocation climb over the secondary gamma' particles, while creep under the condition of low temperature and high stress is controlled by cutting of dislocations through the secondary gamma' particles.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第11期1159-1164,共6页
Acta Metallurgica Sinica
