显微组织均匀性对片层Ti-55531合金高周疲劳裂纹萌生的影响

Influence of microstructure homogeneity on high-cycle fatiguecrack initiation of Ti-55531 alloy with lamellar microstructure

摘要:

采用高周拉压疲劳试验，测试了片层Ti-55531合金的室温高周疲劳性能；利用TEM、SEM等分析检测方法，研究了近裂纹源区次生裂纹特征，以及显微组织均匀性对高周疲劳裂纹萌生的影响。结果发现：该片状Ti-55531合金室温高强疲劳强度(σ-1(1×107))可达639 MPa。合金显微组织中含少量晶界α和大量10~50 μm大小的组织不均匀区，疲劳变形时，晶界α处开裂或组织不均匀区内次生αs断裂、αs/βr界面处开裂等萌生微裂纹，促进合金的疲劳失效。

关键词:Ti-55531钛合金;显微组织均匀性;高周疲劳;裂纹萌生

Abstract:

The influence of microstructure homogeneity on crack intiation behavior under high-cycle fatigue (HCF) test at room temperature was studied in Ti-55531 alloy with lamellar microstructure by TEM and SEM methods. The results show that the HCF strength of Ti-55531 alloy could be as high as 639 MPa. However, a small amount of grain boundary (GB) α and a large number of inhomogenious regions in microstructure significantly effect the HCF behavior of lamellar Ti-55531 alloy. Fatigue microcracks mainly initiated at interfaces between αs and β phases owing to their different structure and properties. Moreover, small amount of microcracks initiated at GB α and αs phases during fatigue.

Key words:Ti-55531 titanium alloy; microstructure homogeneity; high-cycle fatigue; crack initiation