GH864合金蠕变/疲劳裂纹扩展速率及a-N曲线分析  

Analysis of Fatigue/Creep Crack Propagations Rates and a-N Curves of GH864 Alloy

作　　者：王璞[1] 董建新[1] 张麦仓[1] 郑磊[1] 谢锡善[1] 

机构地区：[1]北京科技大学,北京100083

出　　处：《稀有金属材料与工程》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)

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.

关 键 词：GH864合金 裂纹扩展速率曲线 a-N曲线 断口分析 蠕变 疲劳 

分 类 号：TG115.57[金属学及工艺—物理冶金]