K44镍基高温合金长期时效过程中γ′相粗化对拉伸性能的影响

EFFECTS OFγ′-PRECIPITATE COARSENING ON TENSILE PROPERTIES OF Ni BASE SUPERALLOY K44 DURING LONG-TERM AGING

研究了一种抗热腐蚀高温合金K44在800,850和900℃经(1-10)×103h长期时效后γ′相的变化和拉伸性能．结果表明,γ′沉淀相的长大动力学符合Lifshitz-Slyozof-Wagner熟化规律,长大激活能为255 kJ／mol．相对较小的γ′相出现与弹性应变能相关的形态不稳定现象．合金屈服强度随时效温度升高和时效时间的延长而降低,可以由Labusch-Schwarz 强化理论来解释,但塑性却出现了波动．合金的强化机制为强相互作用位错对的切割机制．

The effects of long-term aging （800-900 ℃, （1-10）×10^3 h） on the γ＇ coarsening characteristics and the mechanical properties of a corrosion resistant Ni base superalloy K44 have been investigated. SEM observation reveals that the coarsening kinetics of γ＇ follows LSW theory at different temperatures and the activation energy for γ＇ growth is 255 kJ/mol. Morphological instability occured in relatively small γ＇ precipitates during aging process. At room temperature and 900 ℃, the yield strength decreases with increasing aging temperature and aging time, while a fluctuation of elongation was observed. The dependence of the yield stress on particle size is explained by Labusch-Schwarz hardening theory rather than classical strengthening theory on coherency and mismatch strengthening. Shearing of strong-coupled dislocations is dominant strengthening mechanism.