摘要
研究了GH864合金不同保载时间下650℃蠕变/疲劳裂纹扩展行为,分析了裂纹扩展过程中蠕变和氧化的作用,以及a-N曲线的转折点含义。结果表明:保载5s时GH864合金以穿晶断裂为主,疲劳作用占主导;保载90s时GH864合金以沿晶断裂为主,蠕变作用占主导。利用Saxena模型可较好地表征本实验条件下650℃蠕变/疲劳交互作用的裂纹扩展速率曲线,可估算较高应力强度因子和较低应力强度因子的裂纹扩展速率。另外,用Saxena模型可求出蠕变和疲劳的表达式,对比分析高温蠕变/疲劳交互作用的裂纹扩展过程中蠕变和疲劳的作用及所占的比例。最后针对a-Ni/Nf、da/dN-a曲线及da/dN-N曲线变换中出现的拐点,结合断口形貌分析了转折点对应的含义。高温合金及其它材料的裂纹扩展速率曲线也适用于以上曲线分析方法。
The crack propagation behavior of GH864 alloy was studied at 650 oC under fatigue/creep interaction with different dwell time; the effects of creep and oxidation and the meaning of transition point were analyzed in da-dN and a-N curves. The results indicate that the crack growth rate under dwell 90 s is higher than that under dwell 5 s. The alloy is mainly trans-granular fracture under dwell 5 s and the fatigue effect is principle. The alloy is mainly inter-granular fracture under dwell 90 s and the creep effect is dominant. The crack propagation rate curves of fatigue/creep interaction at 650 oC could well be described by Saxena model under the condition of this test. The descriptions could estimate the crack growth rates at lower and higher stress intensity factors. In addition, the expressions of different alloys from Saxena could contrast the effects of fatigue and creep as well as their proportion. At last, the transition points of a-Ni/Nf, da/dN-a and da/dN-N curves were obtained and the meaning of these points was analyzed with fracture analysis. The curve analysis method can also be used for the crack propagation rate curves of superalloys and other materials.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2011年第4期630-634,共5页
Rare Metal Materials and Engineering
基金
国家自然科学基金(50771011)
